International Symposium on Physics
and Applications of Laser Dynamics 2012
(IS-PALD 2012)
November 7-9, 2012
Multi-Purpose Building, Room 48424
Department of Photonics
National Cheng Kung University
Tainan, Taiwan
Greetings from Organizing Committee Chairs
Welcome to Tainan, Taiwan!!
On behalf of the symposium committee, we sincerely welcome all of you to
Tainan, Taiwan and to the International Symposium on Physics and Applications of
Laser Dynamics 2012 (IS-PALD 2012). This is the 2nd IS-PALD symposium
following the 1st one successfully held in 2011. The symposium attempts to provide
an opportunity to learn advances in physics and applications of laser dynamics,
covering both ultrafast and nonlinear laser dynamics, through invited talks by
renowned scholars and through contributed presentations by active researchers.
Meanwhile, the symposium intends to create an environment for extensive discussion
and potential collaboration with researchers worldwide. Thanks to the great
contributions and submissions from all speakers and authors, the program of IS-PALD
2012 convers various aspects of laser dynamics, ranging from physics to applications
of ultra-short and high-energy laser pulses, from processing to characterization of
ultra-short and high-energy laser pulses, from physics to applications of laser
instability and laser chaos, from generation to control of laser instability and laser
chaos, among others.
We would like to thank all the symposium committee members for their efforts
in organizing IS-PALD 2012. We would also like to thank all speakers and authors for
their great contributions to and for their support for IS-PALD 2012.
We hope you will enjoy IS-PALD 2012 and Tainan, Taiwan.
Sheng-Kwang Hwang
IS-PALD 2012 Co-Chair
Department of Photonics
National Cheng Kung University
Tainan, Taiwan
Ming-Dar Wei
IS-PALD 2012 Co-Chair
Department of Photonics
National Cheng Kung University
Tainan, Taiwan
1
Program
November 7, 2012 (Wednesday)
08:00
|
08:50
Symposium Registration
08:50
|
09:00
Symposium Opening Remark
09:00
|
10:00
Ultrafast Laser
Dynamics (I)
Andrew M. Weiner
(Plenary Talk)
Ultrafast & Broadband Photonic Signal Processing: From
Combs to Microdevices to Control of RF Propagation
10:00
|
10:40
Chair:
Wen-Feng Hsieh
Yin-Chieh Lai
(Invited Talk)
New Laser Dynamics of Modelocked Fiber Lasers
10:40
|
11:00
11:00
|
11:40
11:40
|
12:20
12:20
|
12:40
Coffee Break
Ultrafast Laser
Dynamics (II)
Chair:
Chao-Kuei Lee
Gong-Ru Lin
(Invited Talk)
Nanoscale Graphite and Charcoal Passively Mode-Locked
Er-doped Fiber Laser
Sheng-Lung Huang
(Invited Talk)
Development of a High Repetition Rate 4-Stage Fiber MOPA
for EUV Generation
Wan-Tien Chao
Spectral Compression of an All-Normal Dispersion Fiber
Laser
12:40
|
14:00
Lunch
14:00
|
14:40
Nonlinear laser
Dynamics (I)
Dingyuan Tang
(Invited Talk)
Chaotic Dynamics of a Graphene Mode Locked Vector
Soliton Fiber Laser
14:40
|
15:20
Chair:
Ming-Dar Wei
Fan-Yi Lin (Invited Talk)
Dual-Frequency Laser Doppler Velocimeter for Speckle Noise
Reduction and Coherence Enhancement
2
15:20
|
15:40
Kun-Guei Hong
Dynamic Behavior in the Passive Q-Switched Nd:YVO4
Laser with Pump Modulation
15:40
|
16:00
16:00
|
16:40
16:40
|
17:00
17:00
|
17:40
Coffee Break
See Leang Chin
(Invited Talk)
Intense Femtosecond Laser Filamentation Science in Air
Ultrafast Laser
Dynamics (III)
Chair:
Yin-Chieh Lai
18:00
|
20:00
Takayoshi Kobayashi
Cleaning and Measurement of Femtosecond Pulse by Using
Self-Diffraction Process in Bulk Medium
Seng Hong
(Invited Talk)
AOARD Overview & Research Collaboration Opportunity
Welcome Reception
November 8, 2012 (Thursday)
08:30
|
09:00
Symposium Registration
09:00
|
09:40
Nonlinear laser
Dynamics (II)
Sze-Chun Chan (Invited Talk)
Laser Dynamics for Microwave Photonics: From Narrowband
to Broadband
09:40
|
10:20
Chair:
How-Foo Chen
Frederic Grillot (Invited Talk)
Modeling the Injection-Locking Behavior of Quantum
Cascade Lasers
10:20
|
11:00
Coffee Break
3
11:00
|
11:40
11:40
|
12:00
12:00
|
12:20
Kuan-Wei Su
(Invited Talk)
Self-Mode-Locking of Diode-Pumped Lasers
Ultrafast Laser
Dynamics (IV)
Chair:
Hsiang-Chen
Chui
Chih-Chang Hong
Femtosecond Pulse Compressing and Cleaning by
Self-Diffraction Process
Ting-Wei Chen
Optimal Pulse Characteristics and Pulse Stabilization in a
Hybrid Q-switched Nd:LuVO4 Laser on a Role of Modulation
Frequency
12:20
|
14:00
14:00
|
14:40
14:40
|
15:20
15:20
|
15:40
Lunch
Ultrafast Laser
Dynamics (V)
Chair:
Ming-Che Chan
15:40
|
16:00
16:00
|
16:40
16:40
|
17:00
17:00
|
17:20
Yen-Hung Chen
(Invited Talk)
Laser Pulse Generation and Wavelength Conversion in Single
Nonlinear-Optical Crystal
Shi-Wei Chu
(Invited Talk)
Saturation of Plasmonic Scattering from an Isolated Metal
Nanoparticle
Yu-Kai Sheng
Room-Temperature Excitonic Optical Nonlinearities of
p-Type ZnO Thin Film
Coffee Break
Nonlinear laser
Dynamics (III)
Chair:
Frederic Grillot
Angel Valle (Invited Talk)
High-Frequency Microwave Signal Generation Using
Multi-Transverse Mode VCSELs Subject to Two-Frequency
Optical Injection
Yu-Han Hung
Conversion from Optical Double-Sideband Modulation
Signals to Optical Single-Sideband Modulation Signals Using
Nonlinear Dynamics of Semiconductor Lasers
Ken-Chia Chang
Chaos Suppression in a Nd:YVO4 Laser by Reshaping Pump
Modulation with Dual Waveforms
4
November 9, 2012 (Friday)
08:30
|
09:00
Symposium Registration
09:00
|
10:00
Ultrafast Laser
Dynamics (VI)
Xiaoyi Bao
(Plenary Talk)
The Impact of the Nonlinear Effect in Long Distance
Distributed Brillouin Scattering Sensors
10:00
|
10:40
Chair:
Tzong-Yow Tsai
Shean-Jen Chen
(Invited Talk)
Spatiotemporal Focusing-Based Widefield Multiphoton
Microscopy for Fast optical Sectioning of Thick Tissues
10:40
|
11:00
11:00
|
11:40
11:40
|
12:20
12:20
|
12:40
12:40
|
12:50
Coffee Break
Nonlinear laser
Dynamics (IV)
Chair:
Sze-Chun Chan
Cristina Masoller (Invited Talk)
Rogue Waves in Optically Injected Semiconductor Lasers:
Origin, Predictability and Suppression
Ray-Kuang Lee
(Invited Talk)
Thresholdless Crescent Waves
Angel Valle
Excitability in Vertical-Cavity Surface-Emitting Lasers
subject to Orthogonal Optical Injection
Concluding Remark
5
Organizing Committee & Sponsors
Organizing Committee
Chairs (in alphabetical order):
Sheng-Kwang Hwang (Natinal Cheng Kung Univeristy, Taiwan)
Ming-Dar Wei
(National Cheng Kung University, Taiwan)
Members (in alphabetical order):
Ming-Che Chan
(National Chiao Tung University, Taiwan)
How-Foo Chen
(National Yang Ming University, Taiwan)
Shu-Chun Chu
(National Cheng Kung University, Taiwan)
Hsiang-Chen Chui
(National Cheng Kung University, Taiwan)
Chen-Bin Huang (National Tisng Hua University, Taiwan)
Chao-Kuei Lee (National Sun Yat-Sen University, Taiwan)
Jiunn-Yuan Lin
(National Chung Cheng University, Taiwan)
Chih Wei Luo
(National Chiao Tung University, Taiwan)
Lung-Han Peng (National Taiwan University, Taiwan)
Tzong-Yow Tsai
(National Cheng Kung University, Taiwan)
International Advisory Committee
Members (in alphabetical order):
Silvano Donati
(University of Pavia, Italy)
Wen-Feng Hsieh
Jia-Ming Liu
Junji Ohtsubo
(National Chiao Tung University, Taiwan)
(University of California at Los Angeles, USA)
(Shizuoka University, Japan)
Ci-Ling Pan (National Tsing Hua University, Taiwan)
Jyhpyng Wang (Academia Sinica, Taiwan)
6
Sponsors (in alphabetical order)
Advanced Optoelectronic Technology Center, National Cheng Kung
University, Taiwan
Asian Office of Aerospace Research and Development, Air Force Office of
Scientific Research, U.S.A.
Department of Photonics, Naitonal Cheng Kung University, Taiwan
Ministry of Education, Taiwan
National Cheng Kung University, Taiwan
National Science Concil, Taiwan
7
General Information
Objective and Scope
The Symposium provides an opportunity to learn advances in physics and
applications of laser dynamics through invited talks by renowned scholars and
through contributed presentations by active researchers. Meanwhile, the
Symposium creates an environment for extensive discussion and potential
collaboration with researchers worldwide.
Two areas of laser dynamics are covered in the Symposium:
Ultrafast Laser Dynamics, the topics of which include but are not limited to
(1) Physics and engineering of ultra-short and/or high-energy pulsed lasers
(2) Generation, shaping, and processing of ultra-short and/or high-energy
laser pulses
(3) Detection and characterization of ultra-short and/or high-energy laser
pulses
(4) Applications of ultra-short and/or high-energy laser pulses
Nonlinear Laser Dynamics, the topics of which include but are not limited to
(1) Physics and engineering of nonlinear laser dynamics, including stability,
bistability, periodic and aperiodic dynamics, and chaos
(2) Generation, measurement, shaping, and processing of diverse waveforms
based on nonlinear laser dynamics
(3) Characterization, control, and synchronization of nonlinear laser
dynamics
(4) Applications of nonlinear laser dynamics and their waveforms
Dates
November 7 to November 9, 2012
8
Location
Department of Photonics
National Cheng Kung University
Room 48424, 4th Floor, Multi-Purpose Building
1 University Road, Tainan, Taiwan
Symposium Contacts
Symposium Website: http://conf.ncku.edu.tw/ispald
Chair: Sheng-Kwang Hwang
skhwang@mail.ncku.edu.tw
+886-6-2757575 ext. 63922
Chair: Ming-Dar Wei
mdwei@mail.ncku.edu.tw
+886-6-2757575 ext. 63921
Secretariat: Ms. Emily Hung
em34150@email.ncku.edu.tw
+886-2-2757575 ext. 63900
9
Campus Entrance
Taiwan Railway
Tainan Station
Shangri-La's Far
Eastern Plaza
Hotel Tainan
(Accommodation)
Symposium Venue
(Multi-Purpose Building)
Zenda Suites
(Accommodation)
Campus Entrance
10
11
12
Paper & Summary
Ultrafast & Broadband Photonic Signal Processing:
From Combs to Microdevices to Control of RF Propagation
A.M. Weiner
Purdue University
School of Electrical and Computer Engineering
amw@purdue.edu
Summary
Recent research in the Purdue University Ultrafast Optics and Fiber Communications Laboratory is reviewed,
with a focus on ultrafast and broadband optical signal processing. Three related themes will be discussed.
The first theme comprises generation of high repetition rate frequency combs and pulse trains from continuouswave lasers, either by strong electro-optic modulation [1-2] or nonlinear optics. Line-by-line pulse shaping [3]
is employed to compress such combs into bandwidth-limited pulses, to form optical arbitrary waveforms, and to
yield information on the coherence of the combs generated via nonlinear optics [4].
A second theme involves application of ultrafast optical techniques, including pulse shaping [5-6] and frequency
combs, for ultrabroadband radio-frequency signal processing. Specific topics include agile radio-frequency
arbitrary waveform generation [7-8], photonically implemented RF filtering [9], and spatial and temporal
focusing of ultrabroadband wireless signals distorted by antennas [10] or multiply scattering indoor propagation
environments.
A final theme involves innovative microdevices, implemented in integrated optics in silicon or silicon nitride
films, for signal processing applications. Examples include a programmable RF arbitrary waveform generation
chip [11], nonlinear wave mixing in microresonators for frequency comb generation [4], and a nonreciprocal
transmission device based on nonlinearities in cascaded microresonators [12].
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
R. Wu, V. R. Supradeepa, C. M. Long, D. E. Leaird, and A. M. Weiner, "Generation of very flat optical frequency
combs from continuous wave lasers using cascaded intensity and phase modulators driven by tailored radio
frequency waveforms," Opt. Lett., vol. 35, pp. 3234-3236, 2010.
V. R. Supradeepa and A. M. Weiner, "Bandwidth scaling and spectral flatness enhancement of optical frequency
combs from phase-modulated continuous-wave lasers using cascaded four-wave mixing," Opt. Lett., vol. 37, pp.
3066-3068, 2012.
Z. Jiang, C. B. Huang, D. E. Leaird, and A. M. Weiner, "Optical arbitrary waveform processing of more than 100
spectral comb lines," Nature Photonics, vol. 1, pp. 463-467, 2007.
F. Ferdous, H. Miao, D. E. Leaird, K. Srinivasan, J. Wang, L. Chen, L. T. Varghese, and A. M. Weiner, "Spectral
line-by-line pulse shaping of on-chip microresonator frequency combs," Nature Photonics, vol. 5, pp. 770-776,
2011.
A. M. Weiner, "Femtosecond pulse shaping using spatial light modulators," Rev. Sci. Instr., vol. 71, pp. 19291960, 2000.
A. M. Weiner, "Ultrafast optical pulse shaping: A tutorial review," Optics Communications, vol. 284, pp. 36693692, Jul 2011.
C. B. Huang, D. E. Leaird, and A. M. Weiner, "Synthesis of Millimeter-Wave Power Spectra Using TimeMultiplexed Optical Pulse Shaping," IEEE Photonics Technology Letters, vol. 21, pp. 1287-1289, 2009.
V. Torres-Company, A. J. Metcalf, D. E. Leaird, and A. M. Weiner, "Multichannel Radio-Frequency Arbitrary
Waveform Generation Based on Multiwavelength Comb Switching and 2-D Line-by-Line Pulse Shaping," IEEE
Photonics Technology Letters, vol. 24, pp. 891-893, 2012.
13
[9]
[10]
[11]
[12]
V. R. Supradeepa, C. M. Long, R. Wu, F. Ferdous, E. Hamidi, D. E. Leaird, and A. M. Weiner, " Comb-based
radiofrequency photonic filters with rapid tunability and high selectivity," Nature Photonics, vol. 6, pp. 186-194,
2012.
J. D. McKinney, D. Peroulis, and A. M. Weiner, "Dispersion limitations of ultra-wideband wireless links and their
compensation via photonically enabled arbitrary waveform generation," IEEE Transactions on Microwave Theory
and Techniques, vol. 56, pp. 710-719, 2008.
M. H. Khan, H. Shen, Y. Xuan, L. Zhao, S. J. Xiao, D. E. Leaird, A. M. Weiner, and M. H. Qi, "Ultrabroadbandwidth arbitrary radiofrequency waveform generation with a silicon photonic chip-based spectral shaper,"
Nature Photonics, vol. 4, pp. 117-122, 2010.
L. Fan, J. Wang, L. T. Varghese, H. Shen, B. Niu, Y. Xuan, A. M. Weiner, and M. H. Qi, "An All-Silicon Passive
Optical Diode," Science, vol. 335, pp. 447-450, 2012.
Biography
Andrew M. Weiner graduated from M.I.T. in 1984 with an Sc.D. in electrical engineering. Upon graduation he
joined Bellcore, first as Member of Technical Staff and later as Manager of Ultrafast Optics and Optical Signal
Processing Research. Prof. Weiner moved to Purdue University in 1992 and is currently the Scifres Family
Distinguished Professor of Electrical and Computer Engineering. His research focuses on ultrafast optics signal
processing and applications to high-speed optical communications and ultrawideband wireless. He is especially
well known for his pioneering work on programmable femtosecond pulse shaping using liquid crystal modulator
arrays.
Prof. Weiner is author of a textbook entitled Ultrafast Optics (Wiley, 2009), has published six book
chapters and over 250 journal articles, and is inventor of 13 U.S. patents. Prof. Weiner is a Fellow both of the
Optical Society of America and of the Institute of Electrical and Electronics Engineers (IEEE) and is a member
of the U.S. National Academy of Engineering. He has won numerous awards for his research, including the
Hertz Foundation Doctoral Thesis Prize (1984), the Adolph Lomb Medal of the Optical Society of America
(1990), the Curtis McGraw Research Award of the American Society of Engineering Education (1997), the
International Commission on Optics Prize (1997), the Alexander von Humboldt Foundation Research Award for
Senior U.S. Scientists (2000), and the IEEE Photonics Society Quantum Electronics Award (2011). He is joint
recipient, with J.P. Heritage, of the IEEE LEOS William Streifer Scientific Achievement Award (1999) and the
OSA R.W. Wood Prize (2008) and has been recognized by Purdue University with the inaugural Research
Excellence Award from the Schools of Engineering (2003) and with the Provost's Outstanding Graduate Student
Mentor Award (2008). In 2009 Prof. Weiner was named a U.S. Dept. of Defense National Security Science and
Engineering Faculty Fellow. Additionally, a number of Prof. Weiner’s 27 graduated Ph.D. students have been
selected for student awards & fellowships from the IEEE Photonics Society and Optical Society of America.
Prof. Weiner has served as Co-Chair of the Conference on Lasers and Electro-optics and the
International Conference on Ultrafast Phenomena, as Secretary/Treasurer of the IEEE Lasers and Electro-optics
Society (LEOS), and as a Vice-President of the International Commission on Optics (ICO). He has also served
as Associate or Topical Editor for Optics Letters, IEEE Journal of Quantum Electronics, and IEEE Photonics
Technology Letters. Most recently Prof. Weiner served a three year term as Chair of the National Academy of
Engineering’s U.S. Frontiers of Engineering Meeting.
14
New Laser Dynamics of Mode-Locked Fiber Lasers
Yinchieh Lai
Department of Photonics
National Chiao Tung University
Hsinchu, Taiwan
Email: yclai@mail.nctu.edu.tw
Summary
We have investigated several new types of mode-locked fiber lasers in recent years. These lasers include the
high-repetition-rate asynchronous harmonic mode-locked fiber lasers [1-3], the high-pulse-energy passive
mode-locked fiber lasers, and the passive synchronization of two-color passive mode-locked fiber lasers [4-5].
All of these lasers exhibit interesting new laser dynamics and will be reviewed during the talk.
For asynchronous mode-locked fiber lasers, we have found that the asynchronous harmonic mode-locking
technique can also be generalized to rational harmonic mode-locked fiber lasers for further increasing the pulserepetition-rate. Another more interesting result is that the technique can also be generalized to normal dispersion
mode-locked fiber laser systems (i.e., mode-locked Yb-fiber lasers) to produce stable high-repetition-rate pulse
trains in different optical wavelengths. In contrast to previous belief, the nonlinear soliton mechanism in the
anomalous dispersion regime may not be the necessary requirement for the asynchronous mode-locking
technique to be effective. For the physical mechanism of asynchronous mode-locking, the transition boundary
from synchronous to asynchronous mode-locking can be clarified by using the analytical variational method.
We find that the pulse-repetition-rate of asynchronous mode-locking is actually modulation-depth dependent.
This provides a new method to fine-tune the pulse-repetition-rate of asynchronous mode-locked fiber lasers
without changing the cavity length, which may have some advantages for further laser stabilization applications.
For high-pulse-energy passive mode-locked fiber lasers, we have successfully achieved the pulse energy of
more than 100 nJ directly from a passive mode-locked Er-fiber laser with long fiber cavity length, without using
external optical amplification. The high pulse energy is obtained through the reduction of the pulse repletion rate
so that the average power does not increase proportionally. This approach provides a way to efficiently increase
the output optical pulse energy. However, due to the long fiver cavity length, the output pulse width is from subns to 10 ns orders. We have characterized the output pulses by the spectral filtering technique. Large higher
order spectral chirps are found to be the main characteristics for the output pulses from these kinds of long fiber
cavity passive mode-locked fiber lasers. Preliminary pulse compression experiments have been tried with
limited success due to the large higher order spectral chirps, which should also be compensated if one also wants
to obtain short pulse-width from these laser systems.
For passive synchronization of two-color passive mode-locked fiber lasers, we have successfully passively
synchronized a mode-locked Er-fiber laser at the 1550nm wavelength with a mode-locked Yb-fiber laser at the
1060nm wavelength. The passive synchronization can be done either by sharing a common fiber section in the
two lasers or by using the Yb-fiber laser as the master oscillator to synchronize the Er-fiber laser. The actual
physical mechanisms for passive synchronization are made clear by carefully examining the relative pulse
position of the two color pulses experimentally.
To summarize, mode-locked fiber lasers have become a new platform for investigating new nonlinear
mode-locked laser dynamics. Profound new phenomena have been found thanks to the unique properties of fiber
lasers, which should open up many new research opportunities as well as potential new applications.
References
[1] W.‐W. Hsiang, H.‐C. Chang, and Y. Lai, IEEE J. of Quantum Electronics, 46, 299n (2010).
[2] S.-S. Jyu, S.-F. Liu, W.-W. Hsiang, Y. Lai, IEEE Photonics Technology Letters, 22, 598 (2010).
15
[3] W.-W. Hsiang, C.-Y. Lin, N.-K. Sooi, Y. Lai, Optics Express, 14, 1822 (2006).
[4] W.-W. Hsiang, W.-C. Chiao, C.-Y. Wu, and Y. Lai, Optics Express, 19, 24507 (2011).
[5] W.-W. Hsiang, C.-H. Chang, C.-P. Cheng, and Y. Lai, Optics Letters, 34, 1967(2009)
Biography
Yinchieh Lai received the B.S. degree in Electrical Engineering from National Taiwan University, Taipei,
Taiwan, in 1985, and M.S. and Ph.D. degrees in Electrical Engineering & Computer Science from the
Massachusetts Institutes of Technology, Cambridge, MA, U.S.A., in 1989 and 1991 respectively. He joined the
Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan in 1991 and is
currently a professor at the Department of Photonics in the National Chiao Tung University. He became an OSA
Fellow in 2012 with the recognition of his continuing contributions on the theoretical development of quantum
soliton theories as well as on the experimental/theoretical investigation of new types of mode-locked fiber lasers
and fiber devices.
16
Nano-Scale Graphite and Charcoal
Passively Mode-Locked Erbium-Doped Fiber Laser
Gong-Ru Lin
Graduate Institute of Photonics and Optoelectronics,
Department of Electrical Engineering,
National Taiwan University,
Taipei, Taiwan
Email: grlin@ntu.edu.tw
Summary
Passive mode-locking of fiber lasers with nano-scale graphene/graphite/charcoal saturable absorbers is
currently a new stream of investigation in ultrashort pulsed fiber lasers. Since 2009, graphene has been the first
candidate to show its saturable absorption property for passively mode-locking the fiber lasers, which reveal
some remarkable features including fast saturable absorption with femtosecond recovery time, high optical
damage threshold intensity and wideband wavelength tenability [1]. Recently, graphite based materials have
also shown similar optical properties with graphene for ultrafast laser applications [2]. By directly brushing the
graphite nano-particles on the end-face of a single-mode fiber (SMF) and connects with another SMF, the
graphite nano-particle saturable absorber can be easily inserted into the resonant cavity. The passively modelocked erbium-doped fiber laser (EDFL) with graphite nano-partilce is successfully generated by using the direct
brushing method [2]. In particular, charcoal nano-particle is also used to passively mode-lock the EDFL,
indicating that all the carbon based materials containing crystalline graphene phase can be employed as the
saturable absorber [3]. However, both the graphite and the charcoal nano-particle-based passively mode-locked
EDFL pulsewidths are limited in the ps region due to low cavity gain and large absorption loss caused by the
nano-scale particles.
In this work, the passively mode-locked EDFLs with graphite and charcoal naon-particles are demonstrated.
The cavity gain is enhanced by using a high gain erbium-doped fiber amplifier (EDFA) to approve the
pulsewidth shortening. The saturable absorptions of the graphite and the charcoal nano-particle are compared to
show the dependence of the modulation depth and the pulsewidth shortening. Moreover, the cavity dispersion is
well compensated with the appropriate SMF length to avoid the pulsewidth broadening. As a result, the
passively mode-locked EDFLs with the directly imprinted graphite and charcoal nano-particles are produced.
The mode-locked pulsewidths are shortened to 660 fs and 1.08 ps, respectively. Fig. 1 shows the configuration
of the passively mode-locked EDFL system with intra-cavity graphite nano-particles [2].
Fig. 1 Configuration of the passively mode-locked EDFL system with intra-cavity graphite nano-particles. Left inset: the
microscopy image of the fiber end-face. Lower: the SEM image of the graphite nano-particle [2].
References
[1] Q. Bao, H. Zhang, Y. Wang, Z. Ni, Y. Yan, Z. X. Shen, K. P. Loh, and D. Y. Tang, Adv. Funct. Mater. 19,
3077 (2009).
17
[2] Y. H. Lin and G.-R. Lin, Laser Phys. Lett., 9, 398 (2012).
[3] Y. H. Lin and G.-R. Lin, Conference on Lasers and Electro-Optics (CLEO/QELS 2012), 1304607 (2012).
Biography
Gong-Ru Lin received the B.S. degree in Physics from Soochow University, Taipei, Taiwan, R.O.C., in 1990,
the M.S. and the PhD degrees in Electro-Optical Engineering from National Chiao Tung University, Hsinchu,
Taiwan, in 1990 and 1996, respectively. He was the faculty member of several universities in Taiwan from
1997 to 2006. He joined the Graduate Institute of Photonics and Optoelectronics (GIPO) and the Department of
Electrical Engineering at National Taiwan University (NTU) as a full professor in 2006. He is currently
directing the Laboratory of Fiber Laser Communications and Si Nano-Photonics in GIPO, NTU, Taiwan. He is
the Senior Member of OSA, the Senior Member of IEEE, the Fellow of SPIE, the Fellow of IET, and the Fellow
of IOP. He has coauthored more than 200 SCI-ranked journal papers and 240 international conference papers
during his research career. His research interests include femtosecond fiber lasers, fiber-optic communications,
all-optical data processing, nano-crystallite Si photonics, ultrafast photoconductors, and optoelectronic phaselocked loops.
18
Development of a High Repetition Rate 4-Stage Fiber MOPA for
EUV Generation
Sheng-Lung Huang
Institute of Photonics and Optoelectronics
National Taiwan University
Taipei, Taiwan
Email: slhuang@cc.ee.ntu.edu.tw
Summary
Yb doped double-clad fiber (DCF) based master oscillator power amplifiers (MOPAs) have high single-pass gain, low
quantum defect, and high saturation energy, thus have opened a pathway toward a highly efficient, compact, robust, reliable,
and cost-effective laser-produced plasma sources for extreme ultraviolet (EUV) generation. Very recently, multi-kW of
average power can be produced out of a single-mode fiber. Laser diode seeding of the MOPA can enable highly-controlled
nanosecond MOPA system in terms of pulse repetition rate and pulse shape, but the seed source is typically in nano-joule
level or weaker, especially in single mode. Therefore the design of preamplifier becomes significant. In this manner, the
subsequent amplifiers can be seeded more to suppress the inter-pulse amplified spontaneous emission (ASE) for saving the
stored energy, and to enhance the signal amplification for the release of fiber localized thermal load while pump power
arises. The utilization of large-mode-area fibers can scale up the extractable pulse energy, but it is hard to maintain the
quasi-single-mode output when the core diameter is greater than 15 μm. At the latter stages of a MOPA system, forward
pumping scheme is usually advantageous in all-fiber layout because the stimulated Raman scattering (SRS) is most likely to
occur along the later passive delivery fiber. Besides, large seed energy can ease the efficiency loss caused by shortening
active fibers for higher SRS threshold.
Using a double-pass single-mode preamplifier, we obtained an energy 4 times higher than the single-pass configuration
with >36-dB gain. The core-pumped scheme can shorten the active fiber significantly without photo-darkening effect tested
in hours. As a preliminary result, a 15-ns pulse with a record-breaking energy of 250 μJ at 20-kHz repetition rate was
achieved at the output of a 15/130 double-clad fiber. At present, it was verified by experiments that the empirical scaling
law including the influence of SRS and ASE for both active and passive fibers can be envisioned. The viability of further
energy scaling to mJ pulses at the 30/130 DCF output of the fourth-stage MOPA in high repetition rate can be anticipated.
In this talk, the design and experiment results of a 4-stage MOPA will be addressed in terms of energy scalability, ASE
suppression, signal isolation, and SRS limitation.
Biography
Sheng-Lung Huang received the B.S. degree from the Department of Electrical Engineering, National Taiwan
University in 1986, and the M. S. and Ph. D. degrees from the Department of Electrical Engineering, University
of Maryland, College Park in 1990 and 1993, respectively. He joined the Graduate Institute of Photonics and
Optoelectronics (GIPO) and Department of Electrical Engineering, National Taiwan University in 2006. He
served as the Director of GIPO from August 2007 to July 2010. Prior to joining National Taiwan University, he
served as Director of the Institute of Electro-Optical Engineering, National Sun Yat-Sen University from April
2003 to Jan. 2006. His expertise is on fiber based photonics and tomography technologies.
Dr. Huang is a senior member of the IEEE Photonics Society (PS) and a member of the Optical Society of
America and the Photonics Society of Chinese-Americans. He served as the Chairman of IEEE PS (formerly
LEOS) Taipei Chapter, 2005-2006, and was a Topical Editor of Optics Letters from 2005-2011. He is presently
a steering board member, European Master of Science in Photonics (EMSP).
19
Spectral Compression of an All-Normal Dispersion Fiber Laser
Wan-Tien Chao, Hung-Wen Chen, Hsiu-Po Chuang, Shang-Da Yang, and Chen-Bin Huang*
Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan
*robin@ee.nthu.edu.tw
Asbtract The feasibility to achieve large-scale spectral compression on an all-normal dispersion (ANDi) fiber
laser is studied both numerically and experimentally. Our numerical analyses indicate the spectrum of the ANDi
laser can be compressed with a ratio greater than 40 in a dispersion-increasing fiber (DIF), regardless of the
signs of the pulse chirp. Experimentally, a record-high spectral compression ratio of 46.7 is achieved.
In spectroscopic applications, laser sources with high spectral brightness (power density) are essential in
enhancing the signal-to-noise ratio and the reduction of the measurement time. However, typical fs and
supercontinuum sources suffer from low spectral brightness due to their inherent wide bandwidth. An interesting
solution is to perform external laser spectral compression to effectively enhance the spectral brightness through
the redistribution of the energy into a narrow user-desired spectral window. Such spectral narrowing effect was
first explained for a negatively-chirped optical pulse propagating in a normal dispersion optical fiber [1]. It was
demonstrated later, chirped optical pulses within standard single-mode fiber [2] and photonic crystal fiber [3,4]
were also capable of achieving spectral compression. A comb-profiled fiber was used to demonstrate quasiadiabatic soliton spectral compression [5]. Recently, true adiabatic soliton spectral compression using a
dispersion-increasing fiber (DIF) was experimentally demonstrated using a soliton fiber laser [6]. In this paper,
we first present numerical analysis for large-scale spectral compression on an all-normal dispersion (ANDi)
fiber laser [7]. The results indicate the spectrum of the ANDi laser can be compressed with a ratio greater than
40 in a DIF, regardless of the signs of the initial pulse chirp applied. Experimentally, a record-high spectral
compression ratio of 46.7 is achieved by launching 160 fs positively-chirped ANDi laser pulses into a DIF with
linear dispersion ramp.
Figure 1(a) shows the schematics of the setup. The optical source is an ANDi laser with 8 MHz repetition
frequency [7]. The optical spectrum of the ANDi laser is shown in Fig. 1(b), with a 43.5 nm full-width-halfmaximum (FWHM) bandwidth, capable of supporting 139 fs transform-limited pulses. A segment of single
mode fiber (SMF) is used to compensate the normal dispersion of the laser output pulse. The ten percent port of
an optical coupler is used to monitor the power launched into the DIF. The ninety percent port is connected to a
1-km dispersion-flattened DIF. The spectrally compressed optical spectra after the DIF are measured using an
optical spectrum analyzer (OSA).
Fig. 1(a) Schematic experimental setup: SMF, single mode fiber; DIF: dispersion-increasing fiber; PM, power meter; OSA, optical
spectrum analyzer. (b) Initial ANDi laser optical spectrum.
The feasibility over the spectral compression of such ANDi laser is first studied numerically. The
experimental laser spectrum shown in Fig. 1(b) is employed in our numerical studies and the calculations are
performed by solving the generalized nonlinear Schrödinger equation using the split-step Fourier method with
2000 computational steps. In the calculations, the DIF is modeled using a linear dispersion ramp from 0.6 to
13.5 ps/nm/km, an input dispersion slope of 0.07 ps/nm2/km, a loss coefficient of 0.4 dB/km, along with the
nonlinear and Raman coefficients of 3.5 (W-km)-1 and 3 fs, respectively. Figure 2(a) shows the spectral
evolution along the DIF distance of a positively-chirped ANDi laser pulse with a quadratic spectral phase
coefficient of 0.0039 ps2 (pulse broadened to 160 fs). The output spectral FWHM is effectively compressed to
0.86 nm, giving a large spectral compression coefficient of 50.58. On the other hand, Fig. 2(b) shows the
spectral evolution of a negatively-chirped (quadratic spectral phase coefficient of -0.0039 ps2) ANDi laser pulse
20
within the DIF. Surprisingly, the output spectrum can still yield a spectral compression coefficient of 45.31. A
close comparison between the two dispersion regimes show that in the positive chirp case, the compressed
spectrum is red-shifted while no red-shift is noticed when the input pulse is negatively chirped. This finding
could lead to interesting future potential in providing a wavelength tunable source.
Fig. 2 Calculated spectral evolution when (a) positively and (b) negatively chirped 160 fs ANDi laser pulse are injected into the DIF.
Figure 3(a) shows the experimental spectrally compressed optical spectrum after the DIF (blue line) plotted
against the initial ANDi laser spectrum (black line) with an input average power of 62.6 W. The input pulse is
near transform-limited. The FWHM bandwidth of spectrum after DIF is 0.93 nm, giving a record high spectral
compression ratio of 46.7. Figure 3(b) shows the experimental and the calculated compressed optical spectra.
The experiment and calculation are in good agreements.
Fig. 3 (a) Experimental DIF output spectrum giving a spectral compression ratio of 46.7. (b) Experimental (solid blue curve) and
calculated (dot green curve) compressed spectra.
In summary, the feasibility in yielding large spectral compression using an ANDi laser is numerically
studied. A record-high spectral compression ratio of 46.7 is experimentally achieved by launching positively
chirped optical pulses derived from an ANDi fiber laser into a 1-km dispersion-increasing fiber. This work was
supported by the National Science Council in Taiwan under grant NSC 100-2112-M-007-007-MY3, 100-2221E-007-093-MY3 and by National Tsing Hua University grant 101N2081E1.
References
1. S. A. Planas, N. L. Pires Mansur, C. H. Brito Cruz, and H. L. Fragnito, Opt. Lett.18, 699 (1993).
2. B. R. Washburn, J. A. Buck, and S. E. Ralph, Opt. Lett.25, 445 (2000).
3. E. R. Andresen, J. Thøgersen, and S. R. Keiding, Opt. Lett.30, 2025 (2005).
4. A. B. Fedotov, A. A. Voronin, I. V. Fedotov, A. A. Ivanov, and A. M. Zheltikov, Opt. Lett.34, 662 (2009).
5. N. Nishizawa, K. Takahashi, Y. Ozeki, and K. Itoh, Opt. Express18, 11700 (2010).
6. H.-P. Chuang and C.-B. Huang, Opt. Lett.36, 2848 (2011).
7. H.-W. Chen and S.-D. Yang, Proc. IEEE Photonics Conference, WJ3, 2012.
21
Chaotic Dynamics of a Graphene Mode Locked Vector Soliton
Fiber Laser
Dingyuan Tang
School of Electrical and Electronic Engineering
Nanyang technological University
Singapore 639798
Email: edytang@ntu.edu.sg
Photo
Summary
Apart from the stable soliton emission, the passively mode locked soliton lasers can also exhibit a variety of
deterministic dynamics, such as the soliton period-doubling bifurcation and route to chaos, soliton quasiperiodicity and intermittency [1-3]. These experimental results suggest that the solitons formed in a laser are
fundamentally different from those formed in a conservative system, e.g. the solitons formed in propagation of
strong pulses in single mode fibers. A laser is essentially a dissipative system. Soliton formation in a laser
requires the balanced interplay between the dispersion and nonlinearity, and the losses and gain. Such a soliton
is known as a dissipative soliton. Extensive theoretical studies have shown that the dynamics of dissipative
solitons is governed by the complex Ginzburg-Landau equation, which, apart from having stable localized
solutions, also displays bifurcations to chaos [4].
So far the experimental studies on the deterministic soliton dynamics have mainly focused on the dissipative
scalar solitons. Recent experiments have demonstrated the vector soliton operation of passively mode locked
fiber lasers [5]. A vector soliton has two mutually coupled orthogonal polarization components. Comparing
with the scalar solitons, it is expected that a vector soliton would have more complicated dynamics.
We constructed various passively mode locked vector soliton fiber lasers for the experimental investigation
on the vector dissipative soliton dynamics. One of the lasers is an erbium-doped fiber laser passively mode
locked with atomic layer graphene. Like a semiconductor saturable absorber mirror (SESAM), the saturable
absorption of graphene is light polarization insensitive. Through carefully selecting the cavity components to
ensure a small net cavity birefringence, it was found that vector solitons could be easily formed in our fiber
laser. Either the polarization locked or polarization rotation vector solitons was routinely obtained.
Like the case of scalar solitons, we found that as the vector soliton pulse energy became beyond a certain
level, the stable vector soliton emission of the fiber laser gradually evolved into a quasi-periodic evolution state,
as shown in figure 1, where the vector soliton pulse energy quasi-periodically varied with the cavity roundtrips.
The polarization resolved measurement on the vector soliton also showed that the polarization of the vector
soliton rotated quasi-periodically. Detailed experimental studies also revealed that associated with the quasiperiodic vector soliton evolution, an extra set of spectral sidebands appeared on the soliton spectrum, and the
new spectral sidebands exhibited the characteristics of the sidebands of the soliton modulation instability,
which suggests that the quasi-periodic dynamics of the vector solitons is caused by the coherent wave mixing
between the soliton and the dispersive waves in the laser. A similar effect was also observed on the scalar
soliton fiber lasers. However, as a vector soliton has two orthogonal polarization components, it was found that
the soliton modulation instability could occur on either one of the polarization components or both of them
depending on the strength of each of the two polarization components.
The coherent energy exchange between the dispersive waves and soliton resulted in the energy of the
dispersive waves becoming sufficiently strong, eventually the dissipative waves was shaped into a new soliton
in the cavity, and the laser then moved to a multiple soliton operation state. Our experimental results clearly
demonstrated that the ultimate ultrashort optical pulse achievable in a laser is limited by the modulation
instability of the dissipative solitons.
22
Fig. 1 Oscilloscope traces of the vector soliton under quasi-periodic evolution. Blue line: the total vector
soliton pulse train; Green line: the horizontal axis; Red line: the vertical axis.
References
[1] G. Sucha, S. R. Bolton, S. Weiss, and D. S. Chemla, Optics Letters, 20 (17), 1794 (1995).
[2] F. Sanchez, et al , IEEE Journal of Quantum Electronics, 31(3), 481 (1995).
[3] L. M. Zhao, D. Y. Tang, F. Lin, and B. Zhao, Optics Express, 12(19), 4573 (2004).
[4] N. Akhmediev, J. M. Soto-Crespo, and G. Town, Physical Review E, 63, 056602(2001).
[5] H. Zhang, D. Y. Tang, L. M. Zhao, and N. Xiang, Optics Express, 16 (17), 12618 (2008).
Biography
D. Y. Tang received B.Sc. degree in physics from Wuhan University, China in 1983, M.Sc. degree in laser
physics from the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science in 1986 and
Ph.D. degree in physics from the Hannover University, Germany in 1993. From 1993 to 1994, he worked as a
scientific employee at the Physikalisch-Technische Budesanstalt, Braunschweig, Germany. From 1994 to 1997
he was a University Postdoctoral Research Fellow, and from 1997 to 1999 he was an Australian Research
Council (ARC) Postdoctoral Research Fellow, both at the University of Queensland, Australia. From 1999 to
2000 he was a Research Fellow in the Optical Fiber Technology Center (OFTC), the University of Sydney,
Australia. He is currently an Associate Professor in the School of Electrical and Electronic Engineering,
Nanyang Technological University, Singapore. His current research interests include physics and dynamics of
ultrashort pulse lasers, solid state and fiber lasers, laser ceramics and nanophotonics.
23
Dual-Frequency Laser Doppler Velocimeter for Speckle Noise
Reduction and Coherence Enhancement
Fan-Yi Lin
Department of Electrical Engineering
Institute of Photonics Technologies
National Tsing Hua University
Hsinchu, Taiwan
Email: fylin@ee.nthu.edu.tw
Summary
A dual-frequency laser Doppler velocimeter (DF-LDV) with the unique advantages of speckle noise
reduction and coherence enhancement is proposed and studied. Instead of using a conventional single frequency
laser, an optically-injected semiconductor laser operated in a period-one (P1) dynamical state with two optical
frequencies in its spectrum is used as the dual-frequency light source. While lidars and radars using nonlinear
laser dynamics have been widely studied recently, to the beset of our knowledge, this is the first demonstration
of using a dual-frequency implement to mitigate the influence of speckle noise in laser detection with a diffuse
target. Compared to the conventional optical methods that losses the crucial spatial resolution by performing
spatial averaging, the spatial resolution remains intact in the DF-LDV proposed.
With a microwave beat signal of 11.25 GHz carried to and back from the target by the light, the DF-LDV
utilizing the P1 state proposed is shown to possess both the advantages of good directionality, high intensity,
and high spatial resolution from the light and low speckle noise and good coherence from the microwave,
respectively. By phase-locking the two frequency components with a microwave modulation at their detuning,
the coherence of the dual-frequency light source can be further improved and the detection range can be much
extended. To demonstrate the speckle noise reduction and the coherence enhancement of the DF-LDV, the
velocity resolutions with different amounts of speckle noise and at different detection ranges are experimentally
measured and analyzed. To quantify the improvement, the results from the conventional single-frequency LDV
(SF-LDV), DF-LDV without phase-locking, and DF-LDV with phase-locking using the exact same laser are
compared. The velocity resolution of the DF-LDV is shown to improve 8x103 times from 2.5 m/s to 0.31 mm/s
compared with the conventional SF-LDV for a target with a longitudinal velocity vz = 4 cm/s, a transverse
velocity vt = 5 m/s, and at a detection range of 108 m.
Biography
Fan-Yi Lin received his BS degree in electro-physics from the National Chiao Tung University, Taiwan, in 1997
and his MS and PhD degrees in electrical engineering from the University of California, Los Angeles, in 2001
and 2004, respectively. He joined the faculty of the Department of Electrical Engineering and Institute of
Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan as an assistant professor in 2004 and
later became an associate professor in 2010. His current research interests include nonlinear dynamics of
semiconductor lasers, optical injection, optical feedback, optical chaos, microwave photonics, lidar and radar
systems, and optical sensing.
24
Dynamic Behavior in the Passive Q-Switched Nd:YVO4 Laser
with Pump Modulation
Kun-Guei Hong* and Ming-Dar Wei
Department of Photonics, National Cheng Kung University, No.1, University Road, Tainan City 701, Taiwan
*
L78011083@mail.ncku.edu.tw
Asbtract The dynamical behavior in passively Q-switched Nd:YVO4 laser with pump modulation was
studied. Period and chaotic dynamics phenomena were observed at the various modulation frequencies. Since
the system needed to accumulate the power to saturate the absorber, modulating the pump power would vary the
characteristics of the pulse train. The Q-switched pulse laser system can be controlled into specifically periodic
pulse train as the modulation frequency being the ratio of the repetition frequency without modulation. When
the modulation frequency was closed to the pulse repetition frequency, the timing jitter of pulse train became
very stable and the pulse width compared with pulse train without modulation was compressed. The numerical
simulations based on rate equation agree with the experimental results.
Since the passively Q-switched lasers were developed, the instrinsical dynamical problems such as time
jitter and nonlinear dynamics were attracted much attension and many methods were proposed to explore and
control the dynamics. Modulating the cavity loss can reduce the timing jitter of the passively Q-switched laser in
an Nd:YAG laser [1] and B. Cole reported another way modulating the pumping source with pulse signal to
reduce the timing jitter[2]. The deterministic chaos was recently found in a diode-pumped Nd:YAG laser with
Cr4+:YAG saturable absorber based on the laser operating at the fundamental mode [3]. Further, the transverse
competition would induce the chaos in a passively Q-switched laser [4]. In this work, the dynamics of the pulse
train under pump modulation was studied.
To analyze the dynamics of passively Q-switched laser, the rate equation of Q-switched laser[5] is analyzed
by four order Runge-Kutta method. To make a difference to cavity loss modulation, we changed the pumping
rate from CW pumping into P(ω) which is regarded as the gain modulation.
(1)
P (  )  P 0  P m sin(  t   )
Here, P0 is CW pumping rate; P m is modulation depth and ω is modulation frequency. We altered the modulation
frequency of the rate equation to simulate and analyze the nonlinear behavior of passively Q-switched laser. The
pulse repetition frequency without modulation is 8.3 kHz by setting P m to zero. Figure 1 shows the result of
simulation which is pulse duration distribution versus modulation frequency. There is three particular regions
that are period two, period three and the final period one respectively with increasing modulation frequency. The
period two occurred at 4.2~4.5 kHz which is half of repetition frequency. The period three occurred between 5.3
and 5.5 kHz around two-thirds times of the repetition frequency. The period one exactly occurred at repetition
frequency and the timing jitter obviously go down. The other regions distributions were chaotic. Maybe the
modulation will overtake chaos threshold.
Duration ( μ)
Fig. 1. The pulse duration versus modulation frequency by simulating of the modificatory rate equation.
The Fig.2 schematically depicts the experimental setup. A 808nm and 2W diode laser pumped the
Nd:YVO4 laser. The Nd:YVO4 crystal had dimensions 3 × 3 × 1 mm3 with 1 at.% Nd3+ doping. One side of the
25
Nd:YVO4 crystal was coated with an antireflection coating at 808 nm and with a highly reflection coating at
1064 nm as a cavity mirror of the laser. The other side was antireflection coated at 1064 nm to prevent the effect
of intracavity etalons. A three-element cavity was designed to reduce the size of the spot at the position of the
Cr4+:YAG crystal, which has a transmission of 80% and a length of 5 mm, and so is a saturable absorber and is
mounted in a water-cooled cooper block. The intracavity lens had a focal length f = 7.5 cm with a 1.06 μm
antireflection coating. A concave mirror with a radius of curvature of R c = 8 cm served as an output coupler and
the other cavity mirror, and the reflection of is 80%. The structural diagram traces the rays when the distance
between Nd:YVO4 and lens is 4.5 cm and the distance between lens and output coupler equals Rc + f = 15.5 cm .
The parallel ray from Nd:YVO4 is focused at the focal point, which is also the center of curvature of the output
coupler. The pump laser was modulated by adding a function generator which generated the sinusoidal signal.
The 808nm signal and the 1064nm signal connected to the scope.
Fig. 2. The experimental setup with function generator and scope.
The result of the experiment is shown in Fig. 3. With varying modulation frequencies, the duration
distribution occurred period two, period three and period one, respectively at the specific modulatin frequencies.
In experimental situation without moduration, the repetition frequency was 24.5 kHz. The period two occurred
between 12.5kHz and 14 kHz near half of repetition frequency, and the period three occurred around two-thirds
times of the repetition frequency(15.9~17.1 kHz). Moreover,, the period one exactly occurred at repetition
frequency and the timing jitter was suppressed.
Duration ( μ)
Fig. 3. The experimental result which is pulse duration versus modulation frequency.
In summary, modulating the pump source can control the pulse duration behavior. Periodic and chaotic
pulse train were observed at various modulation frequencies. The timing jitter became very small when the
modulation frequency was closed to the repetition frequency. The gain modulation is a way to change the pulse
duration distribution into special pulse signal with special frequency.
References
[1]S.-L. Huang, T.-Y. Tsui, C.-H. Wang, Jpn. J. Appl. Phys. 38, 239-241 (1999).
[2] B. Cole and L. Goldberg, Opt. Express. 17, 1766-1771 (2009).
[3] D. Y. Tang and S. P. Ng, Appl. Lett. 28, 325-327 (2003).
[4] M.-D. Wei, C. H. Chen and K. C. Tu Opt. Express. 12, 3972-3980 (2004)
[5] A. Siegman, Lasers (University Science, Mill Valley, Calif., 1986), ch.26.
26
Intense Femtosecond Laser Filamentation Science in Air
See Leang Chin
Department of Physics, Engineering physics and Optics &
Center for Optics, Photonics and Laser (COPL)
Laval University,
Quebec City, QC, Canada.
Email: slchin@phy.ulaval.ca
Summary
When an intense femtosecond laser pulse propagates in air, it will self-focus resulting in a continuous series
of foci, or a filament [1]. Filaments can be formed remotely at different distances with different lengths, in
principle. With a Ti-sapphire laser at a wavelength of 800nm (invisible), the color of the pulse will be broadened
into the near UV as well as into the infrared after filamentation. This so-called chirped white light laser or
supercontinuum could be used as a remote special purpose ‘illuminator’. The clamped intensity inside the
filament core being high (5x1013/cm2), nonlinear optical phenomena occur inside the filament. Examples are
third and higher harmonics generation, ultrafast birefringence, THz generation, molecular excitation giving rise
to fluorescence, population trapping, molecular alignment, etc. Possible applications to remote detection of
various chem-bio targets and pollutants as well as the induction of condensation (snow and rain making) will
also be discussed.
References
[1] S.L. Chin, ‘Femtosecond Laser Filamentation’, monograph, Springer, (2010). ISBN 978-1-4419-0687-8.
Biography
See Leang Chin graduated from the National Taiwan University with a B.Sc. degree in physics in 1964. He later
earned his M.Sc. and Ph.D. degrees in physics from the University of Waterloo, Canada in 1966 and 1969,
respectively. Since then, he was employed by Laval University in Quebec City, Canada. He is now a full
professor of physics. Since 2001, he became a senior Canada Research Chair Professor in ultrafast intense laser
science in the Department of Physics and in the Center for Optics, Photonics and Laser (COPL). He had been
the director of the Laboratory for Research in Optics and Laser, the predecessor of COPL in the 80’s. During
this period, he initiated and promoted the establishment of the National Institute of Optics in the Quebec City
region. He is a fellow of OSA. He was honored with, among others, the Humboldt Research Award of the
Alexander von Humboldt Foundation in Germany (1999), the honorary doctorate degree of the University of
Waterloo, Canada (2008) and the CAP Medal for Lifetime Achievement in Physics from the Canadian
Association of Physicists (CAP) in 2011.
27
Cleaning and Measurement of Femtosecond Pulse by Using SelfDiffraction Process in Bulk Medium
Takayoshi Kobayashi1,2,3,4, Jun Liu1,2,5
1
Advanced Ultrafast Laser Research Center, University of Electro-Communications,
Chofugaoka 1-5-1, Chofu, Tokyo 182-8585 Japan
2
Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency,
4-1-8 Honcho, Kawaguchi, Saitama 332-0012，Japan
3
Department of Electrophysics, National Chiao Tung University,1001 Ta Hsueh Rd. Hsinchu 300, Taiwan
4
Institute of Laser Engineering, Osaka University, Yamadakami 2-6, Suita 565-0871, Ibaraki 567-0047, Japan
5
State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics,
Chinese Academy of Sciences, Shanghai 201800, China
Author e-mail address:Kobayashi@ils.uec.ac.jp
Asbtract The self-diffraction effect was used to improve temporal contrast of a femtosecond pulse by
more than four-order of magnitudes. This effect was also used to measure a 55fs pulse by the self-referenced
spectral interferometry method.
I. Introduction
Recently, a new four-wave mixing process, cross-polarized wave (XPW) generation process was used to
clean a femtosecond pulse [1]. A new method for pulse measurement called self-referenced spectral
interferometry (SRSI) was developed based on the XPW [2]. By using XPW-based SRSI (XPW-SRSI) method,
single-shot pulses with 15-fs duration have been measured with a high dynamic range [3].
Recently, we found that the self-diffraction (SD) effect, another four-wave mixing process, can also be used
to clean up femtosecond laser pulses. The output pulse of the first-order SD (hereafter termed SD1) signal has
shorter pulse duration, and a smoother and broader spectrum that the incident pulses [4]. It can be used as the
reference pulse in the SRSI method. Moreover, the two generated SD1 signals are spatially well separated from
the two incident beams in the SD process. Therefore, there is no need to use a polarizer which will limit the
contrast improvement and will introduce serious group velocity dispersion (GVD) in the measurement of sub10-fs visible pulses or even longer pulses in the UV.
II. Experiment and results
The experiment was performed based on a commercial Ti:sapphire CPA laser system (Legend-USP,
coherent)[4]. In the pulse cleaning experiment, a 0.5-mm-thick fused silica glass plate was used. The pulse
energy of two incident pulses were 40 and 51 μJ, respectively. The pulse energies of the generated SD1 signals
in two directions were about 5 and 6 μJ. Thus, the energy transfer efficiency from the input laser beam to the
two SD1 beams was about 12%. The information of the pulse contrast was obtained by a second-harmonic
generation (SHG) FROG which needs much lower incident pulse energy and hence is more sensitive to the low
energy noise. Prepulses were intended to be introduced by 50/50 beamsplitters.
Figure 1 shows how the pulse is cleaned. The extraneously introduced components within 1 ps delay are
removed while the main pulse remains. For the SD1 signal, it shows no peak at the same delay time. For the
incident pulse, the SAC peak intensity around ±0.7 ps is about 1.2×10−2 of that of the main pulse. The SAC of
the SD1 signal has a weak peak at the same delay with smaller intensity than 1.2 × 10−6 of that of the main pulse.
It means that the former is four orders of magnitudes smaller than the main pulse and is smaller than the cube of
1.2 × 10−2 (i.e., 1.7 × 10 −6), which is expected for the third-order nonlinear process of SD.
Fig. 1. SAC intensities of the incident pulse (blue-dot curve) and of
the SD1 signals when the glass was Brewster-angle (black-solid
curve) incidence or perpendicular (red-dash-dot curve) to the
incident beams located in the delay time from -6 to 6 ps and with a
5-fs/step resolution
The experimental setup for pulse characterization by SD-SRSI
method is shown in Fig.2. The energies of two incident pulses were
10 and 6 μJ, respectively. The interference spectrum between incident pulse and SD1 was measured by a
spectrometer (StellarNet Inc, EPP-2000_HR) when the time delay between them is sufficiently long. A 0.1-mm-
28
thick fused silica glass plate was located at the center of the focal waist of the concave mirror, where the two
incident beams have nearly plane wavefronts. In this way, the spatial chirp of the SD1 signal was minimized.
Fig.2 Experimental setup. VND: variable-neutral density filter; BS1, BS2, BS3:
50/50 1-mm-thick beamsplitters; SM1: spherical mirror with the curvature radius
of R=-700 mm; FS: 0.1-mm-thick fused silica glass plate; ND: neutral density
filter; SM2: spherical mirror with the curvature radius of R=-1000 mm; EPP2000-HR: high-resolution spectrometer.
Fig.3. (Color online) (a) Spectra of the incident pulse
(red-dotted curve), the SD1 signal (blue-thick solid
curve) and the interference between them (black-thin
solid curve) measured by the high resolution
spectrometer; (b) The retrieved spectrum (blue-thick
solid curve) and spectral phase (blue dash-dotted curve)
using SD-SRSI. The retrieved spectrum (thin black
solid curve) and spectral phase (black dash-dotted
curve) by SD-FROG and the spectrum of the incident
pulse measured by the spectrometer (red dotted curve).
(c) Two-dimensional SD-FROG trace of the incident
pulse; (d) The retrieved temporal intensity profile by
the SD-SRSI (red solid curve) and SD-FROG (black
solid curve).
The spectra of the incident pulse and the SD1 signal were independently measured by the high resolution
spectrometer, and are plotted in Fig. 3(a). The intensity of the incident pulse was reduced by the ND filter to
about three times lower than that of the SD1 signal. The interference spectrum was also shown in Fig. 3(a),
when the delay time between them was about 1.25 ps. The spectral amplitudes of the beam_3 ( E ( ) ) and that
of the SD1 signal ( Eref ( ) ) are linearly calculated by the following equation [2]:
Eref ( )  1/ 2

( S0 ( )  2 f ( ) )  (S 0 ( )  2 f ( ) )
and E ( )  1/ 2


( S0 ( )  2 f ( ) )  ( S0 ( )  2 f ( ) )


where S0 ( )  Eref ( ) 2  E ( ) 2 , f ( )  Eref
( ) E ( ) .
The retrieved laser spectrum of the incident pulse by the calculation with above expression agrees well with the
spectrum measured by the spectrometer, as shown in Fig. 3(c). The spectral phase of the incident pulse is also
retrieved. The pulse was checked by the SD-FROG, as shown in Fig. 3(b). The retrieved spectral phase is nearly
the same for both methods. The retrieved temporal profiles by SD-FROG and SD-SRSI method are both plotted
in Fig. 3(d). The pulse durations were obtained to be about 55 fs by both methods.
Ш. CONCLUSION
In conclusion, SD process was used to clean and measure femtosecond pulse. The temporal contrast was
improved by four-order of magnitudes. Experiment showed SD-SRSI is also an excellent method for pulse
measurement.
References
[1] A. Jullien, O. Albert, F. Burgy, G. Hamoniaux, J.-P. Rousseau, J.-P. Chambaret, F. A.-Rochereau, G.
Chériaux, J. Etchepare, N. Minkovski, and S. M. Saltiel, “10^-10 temporal contrast for femtosecond
ultraintense lasers by cross-polarized wave generation,” Opt. Lett. 30, 920-922 (2005).
[2] T. Oksenhendler, S. Coudreau, N. Forget, V. Crozatier, S. Grabielle, R. Herzog, O. Gobert, and D. Kaplan,
“Self-referenced spectral interferometry,” Appl. Phys. B 99, 7-12 (2010).
[3] A. Moulet, S. Grabielle, C. Cornaggia, N. Forget, and T. Oksenhendler, “Single-shot, high-dynamic-range
measurement of sub-15 fs pulses by SD” Opt. Lett. 35, 3856-3858 (2010).
[4] J. Liu, K. Okamura, Y. Kida, and T. Kobayashi, “Temporal contrast enhancement of femtosecond pulses by
a self-diffraction process in a bulk Kerr medium”, Opt. Express 18, 22245-22254 (2010).
29
AOARD Overview & Research Collaboration Opportunity
Seng Hong, PhD, PE
Program Manager
Asian Office of Aerospace Research & Development (AOARD)
Air Force Office of Scientific Research (AFOSR)
Air Force Research Laboratory (AFRL)
7-23-17 Roppongi, Minato-ku
Tokyo, Japan 106-0032
Office: +81-3-5410-4409
Direct: +81-3-6385-3377
Mobile: +81-90-9311-1609
seng.hong@us.af.mil
hong.aoard@gmail.com
Summary
A brief AOARD History - The Asian Office of Aerospace Research and Development (AOARD) was
established in the Spring of 1992 by Dr. H. Hellwig, director of the Air Force Office of Scientific Research
(AFOSR), with the endorsement of both Major General Rankine, Air Force Technology Executive Officer of the
Air Force Material Command (AFMC), and the Acquisition Office of the Secretary of the Air Force (SAF/AQ).
AFOSR is a directorate of the Air Force Research Lab (AFRL). The office was opened in June 1992 in Tokyo,
Japan, at the Hardy Barracks compound, which has been managed by the U.S. Army since the end of World
War II. The office is collocated with the Office of Naval Research Global and the US Army International
Technology Center - Pacific.
As AOARD Program Manager, my primary objective is to making professional visits to university, government,
and industrial R&D organizations and participation in scientific and technical meetings, to identify areas of
mutual interest and compatibility. Personal contact is often the initial step towards establishing a mutually
beneficial exchange program between the Air Force R&D community and overseas researchers and
organizations.
Biography
Dr. Seng Hong had accepted his current assignment (July 2012) as program manager station at the Asian Office
of Aerospace Research and Development (AOARD) in Tokyo, Japan. His assignment to the AOARD is to serve
as the USAF liaison for collaborative science and technology (S&T) research programs between the Air Force
Research Laboratory (AFRL) and the Asian scientific center of excellence in academia, industry, and
government laboratories.
Dr. Hong previously served as AFRL Technical Project Lead supporting Missile Defense Agency (MDA) Radar
Systems Technology (RST) Trade Study and Antenna Phased Array R&D programs, authored SBIR topics in
EW technology and serve as Technical Team Lead on RF Counter Assessment activities. Prior joining AFRL in
2002, Dr. Hong was a defense contractor with 17 years of system engineering, hardware design, foreign threat
sub-system reverse engineering, RF devices/component characterization & assessment, radar cross section
computation, RF data collection, and flight qualified assurance compliance. As Project Lead, he developed
system specifications, milestone requirements, acceptance tests, assessed preliminary/critical design reviews,
evaluated technical risk, system vulnerability, schedule/budget constraints, and conducted trade study/impact
analysis. His activities included instigating research consortium with academia and defense industry on Multi-
30
Objective Optimize algorithm, Low-Power Density panel array antenna development, and collaborating with
DoD agency, defense industry, Science &Technology Intelligence community, academia, and presenting
technical briefs/conference papers. In addition, Dr. Hong had served on the IEEE NAECON Technical Track
Chair, IEEE APS-URSI Session Chair and Steering Committee, Technical Papers Reviewer, IEEE Dayton
Section PACE Chair, Wright State University Adjunct Professor, and advisor for the National Research Council
AF Summer Faculty Fellowship program.
31
Laser Dynamics for Microwave Photonics:
From Narrowband to Broadband
Sze-Chun Chan
Department of Electronic Engineering,
City University of Hong Kong
Hong Kong, China
Email: scchan@cityu.edu.hk
Summary
Nonlinear dynamics of single-mode semiconductor lasers have enabled generations of optical waves that carry a
variety of microwave signals. In this presentation, we focus on a semiconductor laser subject to continuouswave optical injection from another laser. The injected laser is known to exhibit different nonlinear dynamics
including stable locking, period-one oscillation, period-two oscillation, and chaotic oscillation. These dynamics
are excellent candidates for generating narrowband to broadband photonic microwave signals [1]. For the
period-one oscillation, the emission from the injected laser is modulated by a microwave subcarrier. The
subcarrier microwave frequency can be tuned a few times exceeding the current modulation bandwidth. Our
experiments show that, by introducing optical feedbacks in additional to optical injection, the linewidth of the
microwave subcarrier can be significantly narrowed from the order of 10 MHz down to 100 kHz. The approach
of linewidth narrowing requires no electrical feedback into the laser and thus circumvents electronic bandwidth
limitation. Narrowband photonic microwave at 45 GHz can be obtained. Generation of narrowband photonic
microwave signals is central to novel radio-over-fiber communication systems [2]. For the chaotic oscillation,
the emission from the injected laser is modulated with random-like chaotic signals spanning over a few
gigahertz. The chaotic waveforms generated with optical injection only and without optical feedback
advantageously contain no residual time-delay signatures. The waveform can be easily harnessed for generation
of random bit sequences. Our experiments invoked a combination of oversampling and bits extraction, where
random bit generation at 40 Gbps is achieved using only 2.5 GHz of a much broader chaotic signals [3]. In short,
by simply operating a semiconductor laser in different nonlinear dynamical states, narrowband to broadband
microwave photonic applications can be realized.
The work described in this paper was fully supported by a grant from City University of Hong Kong (Project No.
7002726).
References
[1] S.C. Chan, IEEE Journal of Quantum Electronics 46, 421 (2010).
[2] C. Cui and S.C. Chan, IEEE Journal of Quantum Electronics 48, 490 (2012).
[3] X.Z. Li and S.C. Chan, Optics Letters 37, 2163 (2012).
Biography
Sze-Chun Chan received the B.Eng. degree in electrical and electronic engineering from the University of
Hong Kong, Hong Kong, and the M.S. and Ph.D. degrees in electrical engineering from the University of
California, Los Angeles, in 2001, 2004, and 2007, respectively. He is currently an Assistant Professor of
Electronic Engineering with the City University of Hong Kong, Hong Kong. His current research interests
include laser nonlinear dynamics, microwave photonics, radio-over-fiber technology, optical chaos generation,
and novel applications of semiconductor lasers. Dr. Chan received the Dr. Bor-Uei Chen Scholarship of the
Photonics Society of Chinese-Americans in 2007.
32
Modeling the Injection-Locking Behavior of Quantum Cascade
Lasers
Dr. Frédéric Grillot
Institut Mines-Télécom - Télécom ParisTech
Ecole Nationale Supérieure des Télécommunications
46 rue Barrault, 75634 Paris Cedex 13, France
Email: frederic.grillot@telecom-paristech.fr
Place
Your
Photo
Here
Summary
Because of the intersubband optical transitions, quantum cascade lasers (QCLs) are promising laser sources with
spectra ranging from mid-infrared to terahertz and which are widely used in optical communication, imaging as
well as remote sensing [1]. Although modulation bandwidth up to terahertz has been theoretically predicted [2,
3], recent results have also shown that the latter remains limited to only tens of gigahertz [4, 5]. In order to boost
the modulation properties, an attractive method consists of optically-injected semiconductor lasers. This
experimental technique has been used many times to improve the modulation characteristics of conventional
interband lasers [6,7]. For instance, a record relaxation resonance frequency of 72 GHz associated with a
broadband response of 44 GHz has been reported in an injection-locked quantum well DFB laser [8]. To this end,
a theoretical study has recently reported the impacts of optical injection on the modulation properties of QCLs
[9]. Numerical results demonstrate that injection-locked QCLs show no unstable regime in the locking map
while the modulation bandwidth can be up to 200 GHz with a 10 dB injection ratio.
This paper aims to further study the intensity modulation (IM) properties of injection-locked QCLs, by taking
into account the influences of injection strength, frequency detuning and the linewidth enhancement factor (LEF)
with fast and slow carrier removal rate. Based on a second-order system model, the modulation transfer function
of the injection-locked laser is obtained from a small signal analysis. Calculations show that the modulation
bandwidth is mostly enhanced by increasing the injection strength, while it is little impacted by the frequency
detuning and the LEF. However, both positive detuning and large LEF lead to the peak occurrence in the
modulation response. In comparison with conventional injection-locked interband semiconductor lasers, no preresonance frequency dip occurs in the QCLs’ IM response. Although simulations point out that in the case of
injection-locked QCLs, there is no unstable regime in the locking range as already reported [9], we will show
that such a conclusion is no longer valid as soon as a deeper non-linear dynamics analysis is conducted via a full
rate equation model.
References
[1] S. Kumar, IEEE J. Select. Topics Quantum Electron., 17, 38 (2011).
[2] C. Y. L. Cheung et al., IEEE proceeding Optoelectronics, 144, 44 (1997).
[3] N. Mustafa et al., IEEE Photon. Technol. Lett., 11, 527 (1999).
[4] Y. Petitjean et al., IEEE J. Quantum Electron., 17, 22 (2011).
[5] W. Maineult et al., Appl. Phys. Lett., 96, 021108 (2010).
[6] A. Murakami et al., IEEE J. Quantum Electron., 39, 1196 (2003).
[7] N. A. Naderi et al., IEEE J. Select. Topics Quantum Electron., 15, 1349 (2009).
33
[8] E. K. Lau et al., IEEE J. Quantum Electron. 44, 90 (2008).
[9] B. Meng et al., Optics Express, 20, 1450 (2012).
Biography
Frédéric Grillot was born in Versailles, France, on August 22, 1974. He received the M.Sc. degree from the
University of Dijon, France in 1999, the PhD degree from the University of Besançon, France, in 2003 and the
Research Habilitation from the University of Paris VII, France, in 2012. His doctoral research activities were
conducted with the Optical Component Research Department, Alcatel-Lucent, involving in research on the
effects of the optical feedback in semiconductor lasers, and the impact this phenomenon has on optical
communication systems.
He was with the Institut d’Electronique Fondamentale, University Paris-Sud, Orsay,
France, from 2003 to 2004, where he was engaged in research on integrated optics modeling and on Si-based
passive devices for optical interconnects. From 2004 to 2012, he was working with the Institut National des
Sciences Appliquées, Rennes, France, as an Assistant Professor. From 2008 to 2009, he was a Visiting Professor
with the University of New-Mexico, Albuquerque, involved in research on optoelectronics with the Center for
High Technology Materials. Since October 2012, he has been appointed Associate Professor within the
Communications and Electronic Department, Telecom Paristech, Paris, France. He is a regular reviewer for
several high-impact factor international journals. He is the author or co-author of 46 journal papers, one book,
three book chapters, and more than 100 contributions in international conferences. His current research interests
include advanced laser diodes using new materials like quantum dots for low-cost applications and nonlinear
dynamics in semiconductor lasers. Dr. Grillot is a Senior Member of the SPIE and of the IEEE Photonics
Society as well as a regular Member of the OSA and the ESA.
34
Self-Mode-Locking of Diode-Pumped Lasers
Kuan-Wei Su
Department of Electrophysics
National Chiao Tung University
Hsinchu, Taiwan
Email: sukuanwei@mail.nctu.edu.tw
Place
Your
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Summary
We reported several compact efficient watt-level self-mode-locked (SML) lasers with pulse repetion rate
from GHz to sub-THz recently. Numerous common diode-pumped Nd-doped, Yb-doped solid-state lasers, and
optical-pumped semiconductor lasers all demonstrated the fascinated, somehow stable, continuous mode-locked
lightsource. These pulse lasers with high repetion rate attract interest for applications such as telecomunication,
quantum communication, photonic switching, supercontinuum generation, measurement, and advanced industry
usage. Here we discuss the principles and conditions of SML lasers generally. For some SML lasers we
mentioned, we have been trying to reveal the mechanism or nature tendency behind the specified cavity
configuration.
Fig. 1 Experimental setup for a diode-pumped SML Nd-doped laser. [1].
References
[1] H.C. Liang, Ross C.C. Chen, Y.J. Huang, K.W. Su, and Y.F. Chen, Optics Express 16, 21149 (2008).
[2] H.C. Liang, H.L. Chang, W.C. Huang, K.W. Su, Y.F. Chen, and Y.T. Chen, Applied Physics B 97, 451
(2009).
[3] H.C. Liang, Y.J. Huang, W.C. Huang, K.W. Su, and Y.F. Chen, Optics Letters 35, 4 (2010).
[4] Y.F. Chen, Y.C. Lee, H.C. Liang, K.Y. Lin, K.W. Su, and K.F. Huang, Optics Letters 36, 4581 (2011).
[5] Y.F. Chen, W.Z. Zhuang, H.C. Liang, G.W. Huang, and K.W. Su, Laser Physics Letters, to be published
(2012).
[6] H.C. Liang, Y.C. Lee, J.C. Tung, K.W. Su, K.F. Huang, and Y.F. Chen, “Exploring spatio-temporal
dynamics of an optically pumped semiconductor laser with intracavity second harmonic generation,”
submitted (2012).
Biography
Kuan-Wei Su was born in Kaohsiung, Taiwan (R.O.C.) in 1979. He received the B.S. degree in Physics from
National Chen Kung University in 2001, and the Ph.D. degrees in Electrophysics from National Chiao Tung
University (NCTU) in 2007. Before he entered the graduate school, he served the compulsory military service in
2001-2003. Since 2008, he has been an assistant professor in the Department of Electrophys, NCTU, Taiwan.
His research interests include solid-state lasers, optical-pumped semiconductor lasers, fiber lasers, photonic
devices, nonlinear optics, ultrafast optics, optical wave propagation, laser dynamics, chaotic phenomena, and
applied optical/laser system.
35
Femtosecond Pulse Compressing and Cleaning by SelfDiffraction Process
Chih-Chang Hong1,*, Ying-Kuan Ko1, Chih-Wei Luo1, Atsushi Yabushita1, Takayoshi Kobayashi1,2
1
Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
Advanced Ultrafast Laser Research Center, and Department of Engineering Science, Faculty of Informatics and Engineering, The
University of Electro-Communications, Chofugaoka 1-5-1,Chofu, Tokyo 182-8585 Japan
* hone918@gmail.com
2
Asbtract We demonstrated a simple method for femtosecond pulse compression and clean with self-diffraction
process in a 0.5-mm-thick glass plate.The pulse compressed ratio is about 32% and the energy transform
efficientcy is about 3.4%. Additionally,the temproal profile was improved by this method.
In ultrafast spectroscopy and laser-mater interaction experiments, perfect Gaussian pulses with smooth
spectrum are vitally important. The unwanted signals introduced by the satellite pulses and an uncleaned
Gaussian pulse usually make experiments complicated [1]. Based on self-diffraction (SD) process in Kerr
medium [2], here we demonstrated a simple experimental setup for compressing and cleaning the femtosecond
pulses.
SD process is a cascaded third-order nonlinear process [3], the intensity of the first-order SD signal
(referred to henceforth as SD1) is a cubic dependence on the intensity pulse. In time domain, it can be simply
expressed as: I sd 1  I 21 (t ) I1 (t   ) . In a non-resonant electronic Kerr medium, the SD process is an
instantaneous process with femtosecond timescale because of inertia-free interaction. The SD signals are well
spatially separated from two input beams.
This study was performed based on a commercial Ti:sapphire chirp pulse amplified laser system (Legend,
Coherent) with the pulse duration of 69 fs and pulse repetition rate of 5 kHz. The pulse with pulse energy of
about 360 µJ was used in the experiments as shown in Fig. 1. The 0.5-mm-thick glass plate was located after the
focal point with ~50 mm. The diameters of both beams on the glass plate were about 1 mm without white light
generation. The crossing angle between two incident laser beams was about 1.2°. The transmitted pulse energies
of beam_1 (Ref1) and beam_-1 (Ref-1) after the glass plate were 36 µJ and 31 µJ, respectively. The pulse energy
of generated SD-1 signal was about 1.05 µJ. Then, the energy transfer efficiency from the input laser beams to
the SD-1 signal was about 3.4%. The characteristics of the pulse width and quality were measured by a noncollinear second harmonic generation (SHG) autocorrelator.
Fig. 2(a) shows the autocorrelation traces and Gaussian pulse fitting curves of Ref-1 and SD-1 signals. One
can see that the pulse duration of SD-1 signal is about 47.3 fs, which is shorter than that of Ref-1, and the pulse
compression ratio is about 32%. Moreover, the pulse shape of Ref-1 is not a pure Gaussian pulse with two
shoulders at ± 100 fs. In Fig. 2(b), we defined the “difference” as the difference between the experimental data
and the fitting curve for both Ref-1 and SD-1 signals. The pulse shape of SD-1 signal is the pure Gaussian pulse
without any shoulders in temporal profile due to the self-diffraction. Besides, the self-focusing process also
enhanced the intensity of main pulse and then reshaped the temporal profile of pulse.
36
Fig. 1 (a) Experimental setup and (b) photography of self-diffraction pattern. BS1 and BS2 are pellicle beamsplitters with the same
45/55 reflection/transmission ratio. SM1: spherical mirror (R=-400 mm). GP: 0.5-mm-thick glass plate. OAPM: off-axis parabolic mirror
(f=10 cm).
Fig. 2 (a) SHG intensities of incident pulses (black solid points) and SD1 signal (black opened points) with a resolution of 1-fs/step. (b)
The difference between SHG intensity and Gaussian pulse fitted curve of incident pulse (black line) and SD1 signal (gray line).
In conclusion, we have demonstrated a simple experimental setup with self-diffraction process in Kerr
media not only for improving the temporal profile but also to compressing the pulse width of femtosecond
pulses. All these outstanding performances make the SD process to be a useful method for designing a
broadband spectrum and a high pulse energy laser system.
[1] J. Liu, K. Okamura, Y. Kida, and T. Kobayashi, Chinese Optics Letters, 051903-1-051903-3 (2011)
[2] J. Liu, K. Okamura, Y. Kida, and T. Kobayashi, Optics Express 18, 22245-22254 (2010)
[3] J. Liu, K. Okamura, Y. Kida, and T. Kobayashi, Optics communication 283 1114-1123 (2010)
37
Optimal Pulse Characteristics and Pulse Stabilization in a
Hybrid Q-Switched Nd:LuVO4 Laser on a Role of Modulation
Frequency
Ting-Wei Chen1(陳挺煒), Ken-Chia Chang1(張肯嘉), Ja-Hon Lin2(林家弘), Ming-Dar Wei1,*(魏明達)
1
Department of Photonics, National Cheng Kung University, No.1, University Road, Tainan City 701, Taiwan
Department of Electro-Optical Engineering & Institute of Electro-Optical Engineering, National Taipei University of
Technology, Taipei 10608, Taiwan
*
mdwei@mail.ncku.edu.tw
2
Asbtract This work achieves a hybrid Q-switched Nd:LuVO4 laser with an acoustic-optic modulator (AOM) and
a Cr4+:YAG saturable absorber. The characteristics of pulse were ramped periodically as the modulation
frequency of AOM was increased. The mechanism with unsaturated absorber in a switched cycle of the AOM
was proposed to explain the behaviors. The ramped behavior by varying the modulation frequency could be
used to optimize the characteristics of pulse in a hybrid Q-switched laser system. Moreover, instabilities of the
pulse and pulse train were observed and discussed.
The techniques of Q-switching are extensively employed for the generation of high-power pulses in lasers.
The Q-switched techniques can be classified into two types corresponding to passive and active Q-switching. In
these Q-switched laser systems, diode-pumped Q-switched lasers have attracted much interest owing to their
wide applications in industry, military, engineering, and scientific research. Nd-doped vanadate crystal has
played a crucial role as a laser medium because of its high conversion efficiency, reliable and compact
performance as well as good beam quality. Various CW and Q-switched lasers have been realized with Nddoped vanadate crystals such as Nd:YVO4 and Nd:GdVO4. Compared with Nd:YVO4 and Nd:GdVO4,
Nd:LuVO4 not only has larger absorption and emission cross sections but also preserves high thermal
conductivity. The studies of various Nd:LuVO4 lasers have been reported so far.
Recently, a hybrid Q-switching with both passive and active elements was proposed to perform a pulse
operation. The hybrid Q-switched laser was realized in use of a spinning mirror and saturable dye in 1966. In
Nd-dopant lasers, a hybrid Q-switched laser simultaneously having the active and passive elements was
proposed for reducing the pulse width and generating tunable repetition frequencies at a fixed pump power with
minimized timing jitter. Because Nd:LuVO4 has large emission cross-section, the satellite pulse and nonlinear
dynamical behaviors easily exist in the passively Q-switched system with a saturable absorber. Moreover, in an
actively system, AOM plays the dominant role not only for Q-switched envelope but also for mode-locked
pulses generation. The competition between Q-switching and mode-locking will induce the dynamical
instabilities, hence the stabilization of solid-state pulsed lasers and the art of how to manipulate and achieve a
better pulsation are still required in many applications.
Since passive and active Q-switching simultaneously operate in a system, the mechanism of mutual
interaction is important to optimize the characteristics of the pulse operation. In a Q-switched fiber laser using
optically driven saturable absorber modulator [1], the pulse repetition rate varied periodically with the
modulation frequency starting from the free-running frequency of the saturable absorber. A locking bandwidth
exists for a pump power that can be used to reduce the pulse timing jitter. However, the behaviors as the
modulation frequency being below the free-running frequency were not included. In a co-doped Cr4+Nd3+:YAG
laser [2], a reduced timing jitter and periodic repetition frequency have also been reported, but the mechanism
has not been elucidated.
In this work, the pulse width reduction and stabilization of the pulse train were experimentally examined in
an Nd:LuVO4 laser with an AOM and a Cr4+:YAG saturable absorber by using dual loss modulation [Fig. 1].
How the pulse characteristics were varied by tuning the modulation frequency of the AOM under a fixed pump
power was discussed in detail [Fig. 2]. Therefore, an approach to optimize pulse width and peak power was
proposed. When the modulation frequency of the AOM is 4.5 kHz, the shortest pulse width and the highest peak
power at 1.06 μm were 28 ns and 0.975 kW at a pump power of 9 W, respectively.
In conclusion, a hybrid Q-switching configuration with acoustic-optic modulator and Cr4+:YAG saturable
absorber was achieved in a diode-pumped Nd:LuVO4 laser. The hybrid Q-switched system can significantly
38
suppress the single Q-switching instabilities and shorten pulse width with stable pulse train. Repetition
frequency and pulse width were ramped in a periodic manner as the modulation frequency of the AOM is varied
at a specific pump power. The locally minimal pulse width happened when the modulation frequency
corresponded to an intrinsic frequency or multiple harmonics of passive-Q-switching-operation repetition
frequency. This could be the criteria to optimize the required pulse characteristics for a specific application.
Finally, the dynamics and instabilities of the pulse train were discussed prior to the harmonics of the saturable
absorber, which is correlated to the subsequent suppression of timing jitter and reduction of pulse width.
Fig. 1 Schematic of the hybrid Q-switched Nd:LuVO4 laser.
Fig. 2 Dependence of (a) repetition frequency, (b) average output power, (c) pulse width and (d) peak power on the modulation
frequency of AOM at the pump power of 6 W. All four figures share the same abscissa.
References
[1] S.K. Hwang anT. Hakulinen, R. Koskinen and O. G. Okhotnikov, Opt. Express, 16, 8720-8726 (2008).
[2] Xuejun Wang and Zuyan Xu, Appl. Opt. 45, 8477-8483 (2006).
39
Laser Pulse Generation and Wavelength Conversion in Single
Nonlinear-Optical Crystal
Yen-Hung Chen
Department of Optics and Photonics
National Central University
Jhongli, Taiwan
Email: yhchen@dop.ncu.edu.tw
Summary
LiNbO3 is a versatile optical material for many applications in such as laser, communication, storage,
information systems because of its superior nonlinear-optic (NLO), electro-optic (EO), acousto-optic, and
piezoelectric properties. In this work, we report our recent studies and developments on the integration of the
NLO and EO effects of LiNbO3 in a solid-state laser system to achieve simultaneously the laser pulse generation
and wavelength conversion. This is done by engineering a special domain structure in single LiNbO3 crystal to
form an optical superlattice to allow the simultaneous performance of the quasi-phase-matched (QPM) EO laserQ control and nonlinear wavelength conversion processes in a laser system. With this unique technique, we have
successfully constructed and demonstrated high-peak-power pulsed second-harmonic-generation (SHG), sumfrequency-generation (SFG), and optical-parametric-oscillation (OPO) laser systems [1-3]. Figure 1 shows the
schematic arrangement of a representative pulsed intracavity wavelength converter realized by this integrated
NLO technique, where an efficient pulsed orange source in a diode-pumped, collinear dual-wavelength (1064
and 1342 nm) Nd:YVO 4 ISFG system using two EO Q switches working based on the QPM EO polarizationmode conversion mechanism [2] is demonstrated. Figure 2 shows the measured output performance of the
system pumped at 4.8-W diode power.
CH1: 1064 & 1342 nm
1.0
M1
Nd:YVO4
coupling lens
voltage pulser 2
PPLN EO
Q-switches
electrodes M2
Intensity (A.U.)
Fiber coupled
809-nm laser diode
voltage pulser 1
M3
BIBO
y
z
x
1 cm 1.3 cm
Oven
L2=7.2 cm
L1
λ=593 nm
CH2: 1064 nm
CH3: 593 nm
1.0
(a)
Q= 25 ns
at L1/L2=1.46
1.0
(b)
(c)
 Q= 0 ns
0.8
0.8
0.8
0.6
0.6
0.6
0.4
0.4
0.4
0.2
0.2
0.2
 Q= 75 ns
12 ns
0.0
-100
0.0
0
100
200
-100
0.0
0
100
200
-100
0
100
200
Time (ns)
Fig. 1 Schematic of a pulsed 593-nm ISFG system constructed in a
diode-pumped, collinear dual-wavelength Nd:YVO4 laser using two
PPLN EO Q switches.
Fig. 2 Measured oscilloscope traces of the two infrared
laser pulses (dashed line), the 1064-nm laser pulse alone
(black line), and the 593-nm SFG pulse (gray line) from
the laser system arranged at L1/L2~1.46 and operated at
 Q= (a) 25 ns, (b) 0 ns, and (c) 75 ns.
Moreover, a compact, tunable pulsed intracavity OPO (IOPO) was also demonstrated in a diode-pumped,
1064-nm Nd:YVO4 laser based on a 2D periodically poled lithium niobate (PPLN) crystal for simultaneously
being an EO Bragg Q-switch and an optical parametric gain medium [3]. When driving the 2D PPLN with 140V pulses at 1 kHz, we obtained a signal at 1550 nm from the IOPO system with a pulse energy of ~9.7 μJ,
corresponding to a peak power of ~2.4 kW, at 9.1-W diode pump power. We also observed multi-wavelength
parametric generation from the system, as predicted from the characteristic phase-matching schemes in the 2D
nonlinear photonic crystal structure.
40
References
[1] Y. H. Chen, W. K. Chang, C. L. Chang, and C. H. Lin, Opt. Lett. 34, 1711 (2009).
[2] W. K. Chang, Y. H. Chen, and J. W. Chang, Opt. Lett. 35, 2687 (2010).
[3] W. K. Chang, Y. H. Chen, H. H. Chang, J. W. Chang, C. Y. Chen, Y. Y. Lin, Y. C. Huang, and S. T. Lin,
Opt. Express 19, 23643 (2011).
Biography
Dr. Yen-Hung Chen was born in 1968 in Taichung, Taiwan, R.O.C. He received the B.S. degree in nuclear
engineering in 1991 and the M.S. and Ph.D. degrees in nuclear science in 1999 from National Tsinghua
University (NTHU), Hsinchu, Taiwan. Between 1999 and 2003, he was with the Department of Electrical
Engineering, NTHU as a postdoctoral research associate. In February 2004, Dr. Chen joined the faculty of the
Department of Optics and Photonics (DOP), National Central University (NCU), Taiwan as an assistant
professor and later as an associate professor since August, 2008. His research interests are in the area of
nonlinear optics, integrated multi-function bulk and waveguide laser devices, solid-state lasers, and ion optics.
41
Saturable and Switchable Scattering of Plasmonic Structures
Shi-Wei Chu
Department of Physics
National Taiwan University
Taipei, Taiwan
Email: swchu@phys.ntu.edu.tw
Summary
The study of surface plasmon resonance (SPR) has recently attracted extensive interest because it provides
light manipulation capability for photonic integrated circuits, nano laser, biosensing, and near-field
superresolution imaging applications 1-4. The spatial resolution of plasmonic nano-imaging can be improved by
incorporating nonlinear optical phenomenon, such as coherent anti-Stokes Raman scattering 5 and saturation.
During the last decade, the diffraction limit of resolution was beautifully overcome by manipulating the on/off
switching of fluorophores 6-8, or by saturation of fluorescence emission 9-11, resulting in resolution below 100 nm.
Nevertheless, fluorescence exhibits intrinsic photobleaching issue. The on/off switching techniques require
repeated excitation of a single fluorophore while the saturation techniques need strong incident power, both
leading to faster bleaching of labeling. Therefore, it will be more than desirable to develop superresolution
imaging modality based on an alternative contrast agent without bleaching, such as scattering.
To our knowledge, neither saturation, nor switching of scattering from SPR structures has been reported, but
there are plenty of reports on saturable absorption of plasmonic nanoparticles embedded in dielectric matrix 12-14.
Since scattering and absorption are related to the real and imaginary parts of electric susceptibility, respectively,
and the two parts are closely linked via Kramer-Kronig relation, in this report, we features the first
demonstration of scattering saturation in an isolated plasmonic nanostructure, and the saturation behavior is
successfully applied to superresolution microscopy. In addition, switchable scattering was demonstrated for the
first time with two perpendicularly polarized laser beams. Since the lifetime of plasmon is on the order of 100
femtosecond, time-resolved spectroscopy are adopted to characterize the ultra-small and ultra-fast switch.
For application of the nonlinearity in scattering, by extracting the saturated part inside the focal region, and
with the aid of extra field localization due to SPR saturation, we have achieved sub-80-nm spatial resolution,
which is enough to resolve the wavelength of surface plasmon polariton in nanoscale optoelectronic devices 15, 16.
Potential applications range from biomedical imaging to functional inspection of plasmonic nanostructures. In
particular, the nonlinear saturation of plasmon is expected to increase resolution of all SPR-related imaging
modalities properties, such as surface-enhanced Raman scattering 17 and apertureless near-field microscopy 18,
which currently exhibits highest optical resolution. We anticipate our demonstration to be a stimulating example
in finding more exotic contrast agency for improving optical resolution.
References
1
2
3
4
5
6
7
8
B. Lee, S. Kim, H. Kim, and Y. Lim, Prog. Quant. Electron. 34, 47 (2010).
S. Lal, S. Link, and N. J. Halas, Nature Photonics 1, 641 (2007).
M. P. Nezhad, A. Simic, O. Bondarenko, B. Slutsky, A. Mizrahi, L. A. Feng, V. Lomakin, and Y. Fainman,
Nat. Photon. 4, 395 (2010).
N. Fang, H. Lee, C. Sun, and X. Zhang, Science 308, 534 (2005).
T. Ichimura, N. Hayazawa, M. Hashimoto, Y. Inouye, and S. Kawata, Phys. Rev. Lett. 92, 220801 (2004).
E. Betzig, G. H. Patterson, R. Sougrat, O. W. Lindwasser, S. Olenych, J. S. Bonifacino, M. W. Davidson, J.
Lippincott-Schwartz, and H. F. Hess, Science 313, 1642 (2006).
S. W. Hell, Science 316, 1153 (2007).
B. Huang, W. Q. Wang, M. Bates, and X. W. Zhuang, Science 319, 810 (2008).
42
9
10
11
12
13
14
15
16
17
18
R. Heintzmann, T. M. Jovin, and C. Cremer, J. Opt. Soc. Am. A-Opt. Image Sci. Vis. 19, 1599 (2002).
M. G. L. Gustafsson, Proc. Natl. Acad. Sci. U. S. A. 102, 13081 (2005).
K. Fujita, M. Kobayashi, S. Kawano, M. Yamanaka, and S. Kawata, Phys. Rev. Lett. 99, 228105 (2007).
H. I. Elim, J. Yang, J. Y. Lee, J. Mi, and W. Ji, Appl. Phys. Lett. 88, 083107 (2006).
G. Piredda, D. D. Smith, B. Wendling, and R. W. Boyd, J. Opt. Soc. Am. B-Opt. Phys. 25, 945 (2008).
I. Ros, P. Schiavuta, V. Bello, G. Mattei, and R. Bozio, Phys. Chem. Chem. Phys. 12, 13692 (2010).
X. H. Huang, S. Neretina, and M. A. El-Sayed, Adv. Mater. 21, 4880 (2009).
C.-Y. Wu, C.-T. Kuo, C.-Y. Wang, C.-L. He, M.-H. Lin, H. Ahn, and S. Gwo, Nano Lett. 11, 4256 (2009).
J. Ando, K. Fujita, N. I. Smith, and S. Kawata, Nano Lett. 11, 5344 (2011).
T. Yano, P. Verma, Y. Saito, T. Ichimura, and S. Kawata, Nat. Photon. 3, 473 (2009).
Biography
Shi-Wei Chu received his B.S. degree in Electrical Engineering from National Taiwan University, Taipei,
Taiwan, in 1999, and M.S. and Ph.D. degrees in Opto-electric Engineering from National Taiwan University in
2001 and 2004, respectively. He joined Department of Physics, National Taiwan University, in 2006, as an
Assistant Professor, and was promoted to Associate Professor in 2010. He has received numerous awards,
including Mediatek Scholarship (2003 – 2004), Outstanding Teaching Award of NTU (2009 – 2011),
Exploration Research Award of Pan Wen Yuan Foundation, Student Thesis Award of Chinese Institute of
Electrical Engineering and Physical Society of Republic of China, and more than 10 best paper awards in
domestic and international conferences. His students also received numerous best paper awards and travel grants
in international conferences. His current research interests cover superresolution microscopy, nonlinear optical
imaging, laser engineering, and functional study of connectome.
43
Room-Temperature Excitonic Optical Nonlinearities of P-Type
ZnO Thin Film
Yu-Kai Sheng1, Ja-Hon Lin1*, Rajalingam Thangavel2, Wen-Feng Hsieh3
1
Department and Institute of Electro-Optical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan.Department
of Photonics
2
3
Institute of Physics, Academia Sinica, Taipei 115, Taiwan
Department of Photonics and Institute of Electro-Optical Engineering , National Chiao Tung University, Hsinchu 300,
Taiwan.
*jhlin@ntut.edu.tw
Asbtract The carrier dynamic around exciton resonace of p-type ZnO produced by codoping with Li+ and N3−
was investigated by transient differential refraction change using the femtosecond Ti:sapphire laser. The
transient reflectance change will be positive above the extion resonance due to bandfilling effect. At exciton
resonance, an obviously two photon absorption effect around zero delay can be seen due to simultaneously
excitation of pump and probe beam.
Introduction
Zinc oxide (ZnO), a kind of II-VI compound semiconductor, has become a potential candidate of
ultraviolet (UV) photonic devices due to its wide direct band-gap of 3.37 eV (wavelength ∼ 368 nm)
and a relative large exciton binding energy (Eb) about 60 meV at room temperature (RT), which is
much higher than other wide band-gap semiconductors such as ZnSe (Eb = 20 meV) and GaN (Eb =
27 meV). For the production of LED or LD in optoelectronics application, the P-type conductivity
is needed but traditionally undoped ZnO exhibits n-type conductivity. Many researchers have tried
to grow up stabilize ZnO possessing p-type conductivity with various technologies. In comparing
with other complex process for producing p-type ZnO, solution-based hydrothermal method is
easier than others. This approach had the advantages of mild synthetic conditions, simple
manipulation and feasibility of large-scale production [1]. Recently, the investigation of ultrafast
carrier dynamics in pure ZnO thin film has drawn a considerable attention using the pump-probe
technique by the femtosecond Ti:sapphire laser [2]. Transient absorption measurements have been
commonly performed in ZnO on time scales of femtosecond (fs) [3]. However, there are few
studies on carrier dynamics in p-type ZnO thin films to observe the refractive index changer owing
to saturation absorption around free exciton resonance by using the degenerate pump-probe method.
In this work, we performed the carrier dynamics in a Li+ and N3- co-doped p-type ZnO sample with
excitation energy states at below band-gap by utilizing the degenerate pump-probe technique at RT
to investigate transient phenomena.
Results and Discussions
The 200 nm thickness Li+ and N3− co-doped ZnO film was deposited on c-cut sapphire substrates by
the sol-gel spin-coating method [1]. The mixture was stirred at 60ºC for 2 hours. Finally, a clear
and transparent homogenous solution was formed. The sol was aged for 24 hours at room
temperature. The sapphire substrate was cleaned in Piranha solution (H2SO4:H2O2 = 3:1), acetone,
and methanol for every 20 minutes by using ultrasonic cleaner and then cleaned with deionized
water and dried under N2 gas. The cleaned sapphire was kept at 120 ºC for 5 minutes and the
coating solution was dropped onto the sapphire substrate, which was rotated at 3000 rpm for 30
seconds by using a spin coater. After spin coating, the film was dried at 300 ºC for 10 minutes on a
hot plate to evaporate the solvent and remove organic residuals. The procedure from coating to
44
drying was repeated ten times. The grown film was then kept in a furnace and annealed in air at
600 and 800 ºC for 1 h.
As reported, the band-gap energy of pure ZnO is 3.37 eV so that exciton resonance energy is
estimated to be 3.298 ev in considering the excitonic binding energy (about 60 meV) of ZnO at RT.
The free carrier dynamics of p-type ZnO below band-gap to near exciton state at RT can be
obtained from the TDRC as shown in Fig. 1. Here, the central wavelength of KLM Ti:sapphire
laser is tuning from 373 to 376 nm (3.324 eV to 3.298 eV). The difference in reflection, ∆R = R
(with pump) − R (without pump), represents the change of reflection through the sample with and
without optical pumping. Figure 1 (a) shows the measured TDRC below band-gap regime (373,
374, and 375 nm). After excitation of the pump beam, an instantaneous rise of ∆R/R for relative
weak probe beam around zero time delay can be seen. Then the photo-generated free carriers
quickly occupy the below band-gap states to quench the further absorption that is what the BF effect
is observed. After zero time delay, the trace will decay in consisting of a fast and two slow decay
terms.
TDRC near free exciton resonance as a function of time delay for excitation wavelengths at 376 nm
(3.298 eV) is show in Fig. 1 (b). Temporal relaxation of excited carriers at this excitation
wavelength is very un-similar to that shown in Fig. 1 (a). Due to free exciton resonance at this
excitation wavelength, a negative dip can be seen resulting from the TPA by simultaneously
absorbing one pump and one probe photon. The similar behavior was observed in transient
transmittance measurement by the UV fs frequency doubling Ti:sapphire laser in GaN sample
below band-gap [4]. After the dip, the TDRC recovers to the origin level and then becomes
negative value and then slowly recover again with relative long recovery time. The expanding of
the time trace near zero decay time is shown inset of Fig. 1 (b). By the fitting in use of the Gaussian
distribution y = A exp(− 4ln(2)2/02), the pulse width  is estimated to be about 157 fs [4].
In order to extract the relaxation times of free-carrier in the p-type ZnO, we use the response
function A1 exp(−t/1) + A2 exp(−t/2) + A3 exp(−t/3) to fit the traces shown in Fig. 1. The three
characteristic time constants 1,  2 and 3, which represent carrier thermalization time, non-radiative
recombination time, radiation recombination time respectively, are show in Table 1. The first decay
time constant 1 in below band-gap regime is around 1 ps due to exciton-phonon scattering. The
second decay time constant is influence by non-radiative recombination with the value about 7-9 ps,
and the third decay time constant is hundreds of picoseconds that is considered to be radiative
recombination time.
373 nm
374 nm
375 nm
F ittin g

-2


20
40
60
T im e D e la y (P S )
80
-5
100

-4
-0 .4
- 0.2
0.0
0 .2
T im e D e la y (p s )
0.4

-4
0
T PA
T P A fittin g
-2
-6
-3
4
0
376 nm
F ittin g
0

6
(b )
-1
-3
R/R (x10 )
8
0
-3

 R/R (x10 )
(a )
0
20
40
60
80
T im e D e la y (P S )
100
Fig. 1 Measured normalized transient differential reflection as a function of time delay with photoexcited energy (a). above
band-gap state (373-375nm) (b). near exciton state with two photon absorption.
45
TABLE. 1 Characteristic time constant around exciton resonance
Wavelength (nm)
1 (ps)
2 (ps)
3 (ps)
373
1.07
7.16
304
374
1.24
7.26
390
375
1.48
9.21
310
376
1.2
1.72
373
Conclusions
The ultrafast carrier dynamics was investigated in a Li+ and N3− codoped ZnO film by utilizing the
reflective pump-probe technique near free excition by the fs laser. The transient reflectance change
will be positive above the extion resonance due to bandfilling effect and can be fitted by the
response function consisting of three terms. Around exciton resonance, an obviously two photon
absorption effect around zero delay can be seen due to simultaneously excitation of pump and probe
beam. Besides, the measured transient reflectance change is zero at serious exciton resonance that
can be explained by the Kramers-Kronig relation.
Acknowledgment
This work was supported by the National Science Council of Taiwan, Republic of China, under
grant NSC 99-2112-M-027-001-MY3.
References
[1] R. Thangavel and Y. C. Chang, Thin Solid Films 520, 2589 (2012)
[2] P. C. Ou, W. R. Liu, H. J. Ton, J. H. Lin, and W. F. Hsieh, J. Appl. Phys., 109, 013102 (2011)
[3] P. C. Ou, J. H. Lin, W. F, Hsieh, Appl. Phys. B, 106, 399 (2012)
[4] C. K. Sun, J. C. Liang, J. C. Wang, F. -j. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl.
Phys. Lett., 76, 439 (2000)
46
High-Frequency Microwave Signal Generation
using Multi-Transverse Mode VCSELs
Subject to Two-frequency Optical Injection.
Angel Valle
Instituto de Física de Cantabria
CSIC-Universidad de Cantabria
Santander, Spain
Email: valle@ifca.unican.es
Summary
1,2
1
Ana Quirce , Angel Valle , Hong Lin3, David W. Pierce3, and Yu Zhang3.
1
Instituto de Física de Cantabria, CSIC-Universidad de Cantabria, Santander, Spain.
2
Departamento de Física Moderna, Universidad de Cantabria, Santander, Spain
3
Department of Physics & Astronomy, Bates College, Lewiston, ME 04240, USA.
Nonlinear dynamics of optically injected semiconductor lasers can be used for photonic microwave
generation [1-3]. This finds applications in radio-over-fiber (RoF) technology that holds great promise for 4G
mobile communications systems [1]. Single-beam [1] and dual-beam optically injected single-mode
semiconductor lasers [2-3] have been considered. Simultaneous injection of two laser beams transforms the
slave laser into a dual-wavelength laser in such a way that the frequency of the generated microwave signal can
be easily tuned by adjusting the frequency spacing between the two master lasers [2-3]. Characterization of the
maximum microwave frequency achievable in a photonic microwave system is of interest because it sets the
bandwidth limit of the system [1]. In this work we propose a new method of photonic generation of microwave
signals using a multimode semiconductor laser subject to dual-beam optical injection. We show that the extra
degree of freedom given by the multimode operation of the semiconductor laser is useful for enhancing the
performance of the photonic microwave generation system.
We have considered a two-transverse mode VCSEL as the multimode semiconductor laser. We have
considered that both transverse modes are linearly polarized in the same direction. Calculations are performed
using a spatially dependent dynamical model of a two-transverse mode VCSEL subject to double beam optical
injection that is parallel [4] or orthogonal to the linear polarization of the two transverse modes. Our calculations
show that double injection locking, and hence broadly tunable microwave signals, can be obtained in these
systems. The response of the two-transverse mode VCSEL is enhanced with respect to that obtained with a
similar single-transverse mode VCSEL subject to the same two-frequency optical injection. The extra degree of
freedom given by the multi-transverse mode operation of the VCSEL under two-frequency optical injection
enhances the performance of the photonic microwave generation system because the higher-order transverse
mode is excited with a much larger amplitude than that of the fundamental transverse mode. Double injection
locking is obtained for a very wide range of frequency detunings between the optical injections and transverse
modes. A relative maximum of the microwave signal amplitude is obtained when the frequency of one of the
optical injections is very close to the frequency of the fundamental transverse mode of the VCSEL. Double
injection locking is demonstrated for symmetric and asymmetric values of the injection strengths. Wide tuning
ranges, extended into the THz band, are obtained in our system. Our results show that the proposed microwave
signal generation mechanism is independent on the polarization of the master lasers.
47
References
[1] X. Q. Qi and J. M. Liu, IEEE J. Sel. Top. Quantum. Electron. 17, 1198 (2011).
[2] Y. S. Juan and F. Y. Lin, IEEE Phot. Journal 3, 644 (2011).
[3] Y. C. Chen, Y. S. Juan and F. Y. Lin, Proc. of SPIE, 7936, 793609 (2011).
[4] A. Quirce and A. Valle, Opt. Exp. 20, 13390 (2012).
Biography
Angel Valle was born in Reinosa, Cantabria (Spain) in 1965. He received the M.Sc. and PhD degrees in Physics
from University of Cantabria, Santander, Spain, in 1988 and 1993, respectively. Between 1993 and 1995 he was
a Postdoctoral fellow with the School of Electronic and Electrical Engineering, University of Bath, UK. Since
1996, he has been with the Instituto de Física de Cantabria, CSIC-University of Cantabria, Santander, Spain,
first as a postdoctoral fellow till 1998 and later as an Associate Professor. His research activities are in
semiconductor lasers, vertical-cavity surface-emitting lasers, noise and nonlinear dynamics of semiconductor
lasers. In these fields he holds more than 70 SCI-stated journal papers and more than 80 publications in
international conference proceedings. He co-chaired the conferences on Semiconductor Laser and Laser
Dynamics at the SPIE Photonics Europe ´2008, ´2010 and ´2012.
48
Conversion from Optical Double-Sideband Modulation Signals
to Optical Single-Sideband Modulation Signals Using Nonlinear
Dynamics of Semiconductor Lasers
Yu-Han Hung1, Cheng-Hao Chu1, and Sheng-Kwang Hwang1,2,*,
1
Department of Photonics, National Cheng Kung University, Tainan, Taiwan
Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan
*skhwang@mail.ncku.edu.tw
2
Abstract Nonlinear dynamics of semiconductor lasers is proposed for optical DSB-to-SSB conversion. Only a
typical laser is required as the conversion unit. Such conversion can be done for microwave frequency up to
hundreds of GHz by simply adjusting input optical power or frequency. This increases flexibility and reconfigurability of the proposed scheme.
Introduction
Radio-over-fiber (RoF) has attracted much research attention for broadband wireless access networks1, which
distributes message-encoded microwave subcarriers over long distances through fibers to remote base stations.
Direct or external modulation of a semiconductor laser is the simplest scheme for such photonic microwave
generation. However, due to the inherent nature of both modulation schemes, optical double-sideband (DSB)
modulation signals are typically generated, which suffer from significant microwave power fading due to fiber
chromatic dispersion2. To minimize the power fading effect, optical single-sideband (SSB) modulation signals
are highly preferred. Therefore, a variety of schemes have been proposed for conversion from optical DSB
signals to optical SSB signals3,4.
In this study, we propose to apply period-one (P1) nonlinear dynamics of semiconductor lasers for DSB-toSSB conversion. As will be demonstrated in the following analysis, such conversion depends solely on the
property of the input optical signal for a given laser. Thus, only a typical semiconductor laser is required as the
main conversion unit. The proposed system can carry out DSB-to-SSB conversion for a microwave frequency
ranging from tens to hundreds of GHz by simply adjusting the input optical power and frequency.
Experiment and Result
The proposed DSB-to-SSB converter is shown in Fig. 1. Basically, it consists of a 1550-nm single-mode
distributed-feedback laser (LD2) which oscillates at a free-running frequency of f2 shown as the blue curve in
Fig. 2(a). LD2 is temperature-stabilized at 25o C and is current-biased at 140 mA, resulting in an output power of
29 mW. For the purpose of demonstration in this study, DSB signals are generated by external modulation of a
1550-nm tunable laser (LD1) which oscillates at f1 shown as the black curve in Fig. 2(a). LD1 is current- and
temperature-stabilized.
To understand the characteristics of P1 dynamics, let us first study the LD2 output when it is subject to CW
light injection from LD1 without applying external microwave modulation. The CW light injection would
attempt to pull the intracavity field oscillation of LD2 toward f1 by locking its optical phase, leading to the
frequency component at f1 shown as the red curve in Fig. 2(a). However, the necessary gain for LD2 is also
modified by the light injection, leading to the change in its cavity refractive index through theantiguidance effect
and thus resulting in the red-shift of its cavity resonance frequency from f2. Such injection-shifted cavity
resonance therefore competes dynamically with the injection-imposed laser oscillation, which radically modifies
the field-carrier coupling of LD2.
Our purpose in this study, however, is to take advantage of such an asymmetric featureof P1 dynamics for
DSB-to-SSB conversion, as demonstrated in Fig. 2(b). When the external modulation with a microwave
frequency of 40 GHz is applied to LD1, the resulting light output exhibits a typical DSB characteristic shown as
the black curve in Fig. 2(b), where modulationsidebands with a frequency spacing of 40 GHz around f1 appear.
Injecting such a DSB signal into LD2 with the same input power and frequency considered in Fig. 2(a) would
generate a SSB signal at the LD2 output, which is shown as the red curve in Fig. 2(b). The lower sideband at f3
is about 17 dB stronger than the upper sideband at f4 and the frequency spacing is exactly the same as the
external modulation frequency, i.e., 40 GHz. The SSB characteristic is sustained even when the external
microwave modulation is encoded with a message of 2.5 Gb/s shown in Fig. 2(c) where slight spectral
broadening around each component occurs.
49
Fig. 1 Schematic of experimental
setup. LD: laser diode; PC:
polarization controller; EM:
external
modulator;
PD:
photodiode; LPF: low-pass filter;
PG: pattern generator; ET: error
tester; LO: microwave local
oscillator; M: microwave mixer.
Fig. 2 Optical spectra. (a) No external microwave modulation is applied to LD1. (b)
External microwave modulation is applied toLD1. (c) External microwave modulation
with an encoded message of 2.5 Gb/s is applied to LD1. Blue curve: free-running LD2;
Black curve: LD1; Red curve: optically injected LD2. The frequency axis is relative to
the free-running frequency of LD2. For clear demonstration, the blue curve is up-shifted
by 20 dB and the red curves are down-shifted by 20 dB from their original values.
Under the same input power and frequency considered in Fig. 2(b), an input optical DSB signal with a
frequency spacing, or equivalently microwave frequency, slightly higher or lower than 40 GHz could also be
successfully converted to an optical SSB signal with exactly the same input microwave frequency if it varies
within a range of about 4.5 GHz around 40 GHz. Different such ranges are observed for different injection
conditions. For input microwave frequency much higher or lower than 40 GHz, the level and/or frequency of the
input optical signals can be simply adjusted to achieve the necessary frequency spacing for successful DSB-toSSB conversion.
To study the quality of the data after DSB-to-SSB conversion, the bit-error ratio (BER) as a function of the
received optical power for the operating condition considered in Fig. 2(c) is analyzed and shown in Fig. 3. The
BER of the input optical DSB signal is also shown. A BER down to 10-10 is achieved after conversion, where
no error floor is observed but a slight power penalty of about 1.3 dB is required. Similar performance
characteristics are observed for other input optical powers or frequencies and for other input microwave
frequencies. This demonstrates the feasibility of the proposed DSB-to-SSB conversion scheme.
Fig. 3 Bit-error ratio as a function of received optical power for an input optical DSB signal (blue symbols) and an output optical SSB
signal (red symbols) under the injection condition considered in Fig. 2(c), where the bit rate is 2.5 Gb/s. The solid curves are for better
visibility.
Conclusion
Period-one dynamics of semiconductor lasers has been proposed and demonstrated for DSB-to-SSB
conversion. Such conversion depends solely on the property of the input optical signal for a given laser, and
therefore only a typical semiconductor laser is required as the main conversion unit. The proposed system can
carry out DSB-to-SSB conversion for a microwave frequency ranging from tens to hundreds of GHz by simply
adjusting the input optical power and frequency. Such conversion can also be achieved without the need of such
an adjustment for microwave frequencies with a few GHz difference.
References
[1] J. O'Reilly and P. Lane,J. Lightwave Technol. 12, 369 (1994).
[2] U. Gliese, S. Norskov, and T.N. Nielsen, IEEE Trans. Microwave Theory Tech. 44, 1716 (1996).
[3] A. Kaszubowska, P. Anandarajah, and L.P. Barry, IEEE Photon. Technol. Lett. 16, 605 (2004).
[4] G.H. Smith, D. Novak, and Z. Ahmed, IEEE Trans. Microwave Theory Tech.45, 1410 (1997).
50
Chaos Suppression in a Nd:YVO4 Laser by Reshaping Pump
Modulation with Dual Waveforms
Ken-Chia Chang* and Ming-Dar Wei
Department of Photonics, National Cheng Kung University, No.1, University Road, Tainan City 701, Taiwan
*
L78001070@mail.ncku.edu.tw
Asbtract This work demonstrates the suppression of chaos in a Nd:YVO4 laser by reshaping pump modulation
with dual waveforms. When the first sinusoidal modulation induced chaos, the second modulated signal with
square, triangle and sinusoidal waveforms would reshape modulated profile to suppress chaos. The suppression
region depended on the shape of the modulation, and the shape could be a parameter to control dynamics.
Numerical simulations were confirmed by experimental results.
Since Ott, Grebogi and Yorke demonstrated the first report to control chaos [1], the control or suppression
of chaos has attracted great research interest. Recently, Chacón presented that the geometrical resonance
provides the mechanism underlying the non-feedback control of chaos based on a dynamical system under a
biharmonic modulation [2]. In solid-state laser systems, this important role of initial phase difference was
discussed in a Nd:YVO4 lasers with biharmonic pump modulation in detail [3]. Moreover, the dynamical
behavior is affected by the shape of the modulation or perturbation [4]. Since the solutions of the many
nonlinear oscillators are given in terms of Jacobian elliptic functions, modulations with the Jacobian elliptic
functions can be used to study the reshaping-induced dynamics [5]. In the lasers, the nonlinear dynamics of a
single-mode bidirectional solid-state ring laser was explored under the influence of square-wave modulation [6].
It is interesting to the role of reshaping modulation profile in a modulated system under dual waveforms. This
work examines the suppression of chaos in a Nd:YVO4 laser with a bi-waveform pump modulation in which the
first modulation for chaos-inducing was sinusoidal and the second modulation for chaos-suppressing was chosen
to be square and triangle as well as sinusoidal. The initial phase difference of these two modulated signals and
modulation depths, defined as the modulation amplitude divided by the average value of the pump intensity,
determined the region of the suppressing chaos [2]. The profile of the second modulation varied the region of
the suppressing chaos. The numerical simulation for the suppressed region agrees closely with that obtained by
experimental result.
Figure 1 schematically depicts the experimental setup for the Nd:YVO4 laser with pump modulation. A diode
laser with a wavelength of 808 nm and a maximum output power of 1 W was collimated by an objective lens
with numerical aperture of 0.47, beam shaped by an anamorphic prism pair, and focused onto the Nd:YVO4
crystal by another objective lens with a focal length of 8 mm. The Nd:YVO4 crystal had dimensions 3×3×1 mm3
and 2 at.% Nd3+ doping. One side of the Nd:YVO4 crystal had an antireflection coating at 808 nm and a high
reflection coating at 1064 nm. This side was also acted as an end mirror of the laser cavity. The other side had
an anti-reflection coating at 1064 nm to reduce the effect of intracavity etalon. A concave mirror with a radius of
curvature of R c = 80 mm and a reflectivity of 90% was used as the other end mirror and the output coupler. The
signal of the intensity and spectrum was measured by a high-speed photodetector together with an oscilloscope
and a RF spectrum analyzer. A cavity length of 60.60 mm was determined by the beating frequency of
longitudinal modes, in which the g 1g2 parameters of the cavity configurations are about 0.265 as considering the
thermal effect.
Fig. 1 The experimental setup: OL, objective lens; OC, output coupler; PD, photodetector; LD, laser diode; FG1 and FG2, function
generator 1 and 2; OSC, oscilloscope; RFSA, RF spectrum.
51
(a)
(b)
Fig. 2 The boundaries of chaos-suppressed regions with various modulation shapes of the second modulations. A periodic
intensity was observed inside each region. (a) experiment results, (b) numerical simulations.
Considering a bi-waveform pump modulation, the equivalent pumping should be represented to
(1)
pumping  pm1 sin( 2f m1t )  pm 2 wf ( 2f m 2t   ) .


The modulation frequency of first modulation resonated to the relaxation oscillation frequency to induce the
chaos. Because the suppression chaos from the second modulation was the focused topic in this work, the
sinusoidal wave was chosen. The term of wf(2fm2t+) represents that the second modulation was an arbitrarily
periodic waveform with a frequency of fm2 and had the initial phase difference,, to the first modulation. Square,
triangle, and sinusoidal waveforms were chosen to examine the chaos suppression depending on the modulation
shape. The frequencies were set to fm2=fm1/2 in the following discussions. Varying p m2 and  will reshape the
sinusoidal waveform generated by the first modulation to suppress the chaotic behavior. Figure 2 (a) depicts the
regions of chaos suppression by varying simultaneously p m2 and when the second modulated waveforms were
chosen to be sinusoidal, square, and triangle, respectivelyObviously, the suppressed regions depended on the
modulation shape. It was agreed with the numerical results that the suppression region had higher p m2 for
triangle modulation and lower p m2 for square modulation than that of sinusoidal modulation, and the central
phase difference between two modulations were around  =220o. In this work, the laser model based on the FoxLi approach [7] was established from the rate equation and the generalized Huygens diffraction integral [8].
Since the standing wave cavity configuration can be unfolded into an equivalent lens guide system, the laser can
be characterized with reference to a cascading propagation of the optical field in the gain medium and the cold
cavity. Above results of numerical simulation was shown in Figure 2 (b). This work investigates the suppression
of chaos in a Nd:YVO4 laser with the pump modulated by dual waveforms. The chaos can be suppressed by
adding the second modulation to reshape the waveform of the pump laser under subharmonic frequency, in
which the shapes of the second modulations were square, sinusoidal, and triangle. The suppression region
depending on the initial phase and the modulation depth of the second modulation would vary owing to the
reshaping. Numerical simulations were verified by the experiments. The authors would like to thank the
National Science Council of the Republic of China for financially supporting this research under Contracts No.
NSC 100-2112-M-006-008.
References
[1] E. Ott, C. Grebogi, and J. A. Yorke, Phys. Rev. Lett. 64, 1196 (1990).
[2] R. Chacón, Phys. Rev. Lett. 77, 482 (1996).
[3] M.-D. Wei, C.-C. Hsu, H.-H. Huang, and H.-H. Wu, Opt. Express 18, 19977 (2010).
[4] R. Chacón, Chaos, solitons Fractals 31, 1265 (2007).
[5] R. Chacón, Control of homoclinic chaos by weak periodic perturbations (World Scientific, Singapore, 2005).
[6] F. Rawwagah and S. Singh, J. Opt. Soc. Am. B 23, 1785 (2006).
[7] A. G. Fox and T. Li, Bell Sys. Tech. J. 40, 453 (1961).
[8] M.-D. Wei, C.-H. Chen, H.-H. Wu, D.-Y. Huang, and C.-H. Chen, J. Opt. A 11, 045504 (2009).
52
The Impact of the Nonlinear Effect in Long Distance Distributed
Brillouin Scattering Sensors
Xiaoyi Bao
Department of Physics
University of Ottawa
Ottawa, Canada
Email: xbao@uottawa.ca
Summary
Rayleigh, Brillouin and Raman scatterings in fibers result from the interaction of photons with local material
characteristic features like density, temperature and strain. For example an acoustic/mechanical wave generates
a dynamic density variation; such a variation may be affected by local temperature, strain, vibration and
birefringence [1]. By detecting changes in the amplitude, frequency and phase of light scattered along a fiber,
one can realize a distributed fiber sensor for measuring localized temperature, strain, vibration and birefringence
over lengths ranging from meters to one hundred kilometers. Such a measurement can be made in the time
domain or frequency domain to resolve location information. With coherent detection of the scattered light or
beat signal measurement one can observe changes in birefringence and beat length for fibers and devices [2],
which is an important parameter for communication system. These distributed sensors can be used for disaster
prevention in the civil structural monitoring of pipelines, bridges, dams and railroads, power generators and
aerospace applications.
Evaluation of the distributed fiber sensors includes three criteria: 1) long sensing length (over 100km); 2) short
spatial resolution (to be able to identify short spatial change, just like image resolution, which means short pulse
duration and broad frequency bandwidth; 3) high temperature or strain resolution, which is proportional to
signal to noise ratio.
Requirement of (3) means high power, for long distance of 100-200km (requirement of (1), it means high
nonlinear effect, such as self-phase modulation (SPM) and modulation instability (MI). Below the threshold of
SPM and MI, long distance transmission of the Brillouin gain signal is still subjected to the Brillouin gain
saturation and depletion, which induces Brillouin spectrum distortion. Hence low resolution for requirement #2
and #3, in addition, short pulse associated broad spectrum will make low power spectrum efficiency for narrow
Brillouin spectrum in fiber (30MHz). There is a trade-off among three requirements. I will talk about ways to
overcome those limitations by different approaches on laser power, choice of optical fibers and time [3], and
frequency [4] manipulations, as well as pulse coding to improve signal quality in spatial domain.
References
[1] X. Bao, L. Chen, “Recent Progress in distributed fiber topic sensors”, Sensors, review paper, 12, 8447-8486
(2012)
[2] Y. Lu X. Bao, L. Chen, S. Xie, M. Pang, Distributed birefringence measurement with beat period detection of
homodyne BOTDR, Opt Lett. In press.
[3] Y. Dong, L. Chen, and X. Bao, “Time-division multiplexing based BOTDA over 100km sensing length” Opt
Lett., 36(2), 277-279 (2011)
[4] Y. Dong, L. Chen, and X. Bao, “Extending the sensing range of Brillouin optical time-domain analysis
combining frequency- division multiplexing and in-line EDFAs”, IEEE J-LT, 30 (8), 1161-1167 (2012)
53
Biography
Xiaoyi Bao, received the B.Sc. and M.Sc. in Physics from Nankai University, China and a PhD in Optics from
Anhui Institute of Optics and Fine Mechanics, Academic Sinica. Her research involves nonlinear effects in
optical fibers and their applications for sensing, lasers, devices and communications. She is a fellow of Royal
Society of Canada (RSC), OSA and SPIE. She received the Ontario Premier's Research Excellence Award in
2001, Ontario Distinguish Researcher Award in 2002, the 1 st University of Ottawa Inventor of the Year Award
in 2003, the Researcher of the Year 2004 from Faculty of Science (U of Ottawa), the NCE (National Centers of
Excellence of Canada) Chair’s Medal in 2006, the Canadian Association of Physics (CAP)-National Optics
Institute (NOI) Medal for Outstanding Achievement in Applied Photonics in 2010. She joined Physics
Department at the University of Ottawa as a full professor in 2000. She is Tier I Canada Research Chair
Professor in Fiber Optics and Photonics.
54
Spatiotemporal Focusing-based Widefield Multiphoton
Microscopy for Fast Optical Sectioning of Thick Tissues
Shean-Jen Chen
Department of Engineering Science
Center for Micro/Nano Science and Technology
National Cheng Kung University
Tainan, Taiwan
Email: sheanjen@mail.ncku.edu.tw
Summary
A microscope based on spatiotemporal focusing offering widefield multiphoton excitation has been developed
to provide fast optical sectioning images. This configuration can produce multiphoton images with an excitation
area larger than 200 × 100 μm2 at a frame rate greater than 100 Hz. Brownian motions of fluorescent microbeads
as small as 0.5 μm were observed in real-time with a lateral spatial resolution of less than 0.5 μm and an axial
resolution of approximately 3.5 μm. Also, second harmonic images of chicken tendons demonstrate that the
developed widefield multiphoton microscope can provide high resolution z-sectioning for bioimaging.
Furthermore, in order to compensate temporal profile distortions, a sensorless image-based adaptive optics
system was integrated into the microscope. The two-photon excited fluorescence image quality of 1 μm
fluorescent beads sealed in agarose gel at different depths is improved.
Keywords: spatiotemporal focusing, widefield multiphoton microscopy, optical sectioning, adaptive optics.
Biography
Shean-Jen Chen received his B.S. degree from National Taiwan University in 1987 and his M.S. degree in
Mechanical Engineering from Columbia University in 1991. In December 1996, he was awarded his Ph.D.
degree for research in adaptive noise cancellation and image restoration at the University of California, Los
Angeles (UCLA). He entered the Synchrotron Radiation Research Center of Taiwan in January 1998 where he
became involved in the development of soft x-ray active gratings and microfocusing optical systems. He is
currently a Professor at the Engineering Science Department and the Director General at the Center of
Micro/Nano Science and Technology of National Cheng Kung University of Taiwan and is actively engaged in
researching plasmonic biosensing & molecular imaging and adaptive optics in biomedical nonlinear optical
microscopy.
55
Rogue Waves in Optically Injected Semiconductor Lasers:
Origin, Predictability and Suppression
Cristina Masoller
Departament de Física i Enginyeria Nuclear
Universitat Politècnica de Catalunya
Terrassa, Barcelona, Spain
Email: cristina.masoller@upc.edu
Summary
Rogue waves are extreme and rare events that occur in many natural systems and a lot of work has focused
on predicting and understanding their origin [1]. In optically injected semiconductor lasers rogue waves are
occasional ultra-high intensity pulses capable of producing catastrophic optical damage. We recently studied),
experimentally and numerically these rogue wave events in an optically injected vertical-cavity surface emitting
laser (VCSEL). We found that the laser output intensity can display two different deterministic chaotic regimes:
one in which rogue waves occur relatively frequent (see Fig. 1), and one in which they are almost inexistent [2].
In this talk I will show that i) the rogue waves can be predicted with a long anticipation time as compared with
the laser characteristic time scales and with the rogue wave characteristic time scale; ii) the rogue waves in the
laser model are generated by a deterministic external crisis-like process and iii) noise strongly affects the
probability of occurrence of rogue waves and can be used either to enhance or to suppress the rogues waves. By
providing a good understanding of the mechanisms triggering and controlling the rogue waves, our results can
contribute to improve the performance and the reliability of optically injected lasers, and can also enable new
experiments to test if these mechanisms are also involved in other natural systems where rogue waves have been
observed.
Fig.1
(left) Experimental time trace of the laser intensity displaying extreme, rogue wave intensity pulses. The experimental setup
consists of a single mode VCSEL (emitting at 980 nm with threshold current at about 0.2 mA), which receives continuouswave optical injection from an external grating tunable semiconductor laser. An optical isolator ensures that the coupling
between the two lasers is unidirectional. The time series of the VCSEL intensity is measured by an amplified photo-detector
(bandwidth DC 9.5 GHz) and recorded by a 6 GHz bandwidth oscilloscope. The VCSEL pump current is 0.97 mA, the
detuning between the VCSEL and the master laser is -1.34 GHz and the injected power is 1.1 mW.
(right) Numerically simulated time series and histogram of the intensity values. A deterministic model [2] was used to
simulate the laser dynamics. A intensity pulse is identified as a rogue wave if is higher than <I> + 8 , where <I> is the
average intensity value and  is standard deviation of the distribution of intensity values. The dashed line in the histogram
indicates the threshold for a high pulse to be considered a rogue wave.
56
References
[1] D. R. Solli, C. Ropers, P. Koonath, and B. Jalali, Optical rogue waves, Nature 450, 1054 (2007).
[2] C. Bonatto, M. Feyereisen, S. Barland, M. Giudici, C. Masoller, J. R. Rios Leite, and J. R. Tredicce,
Deterministic Optical Rogue Waves, Phys. Rev. Lett. 107, 053901 (2011).
Biography
Cristina Masoller received the Bachelor degree in physics from the Universidad de la Republica, Montevideo,
Uruguay, in 1986; the M.Sc. degree in physics from the Universidad de la Republica, in 1991 and the Ph.D.
degree in physics from Bryn Mawr College, Pennsylvania, USA, in 1999. Her PhD thesis was about nonlinear
dynamics of semiconductor lasers with optical feedback, directed by Prof. Neal B. Abraham. In the period
1991–-2004 she was Assistant Professor at the Facultad de Ciencias, Montevideo, Uruguay; in the period 20042009 she was a “Ramon and Cajal” researcher at the Universitat Politecnica de Catalunya (UPC) in Terrassa,
Barcelona, Spain. In May 2009 she was appointed Associate Professor at UPC, in the Departament de Física i
Enginyeria Nuclear. Her current research interests focus on the nonlinear dynamics of semiconductor lasers, and
the influence of external perturbations such as optical feedback, optical injection, current modulation, etc. She
studied the nontrivial interplay of nonlinearities, noise and time-delayed effects due to feedback or coupling.
She has also studied phenomena related to multi-mode emission such as polarization switching, polarization
bistability, hysteresis, multi-longitudinal and multi-transverse mode emission in vertical-cavity surface emitting
lasers and in edge-emitting lasers.
57
Thrresholdless Creescent W
Waves
Ray-Ku
uang Lee
Institutee of Photonnics Technoologies
Nationaal Tsing-Huua Universiity
Hsinchuu, Taiwan
Email: rrklee@ee.nnthu.edu.tw
w
Summaary
With microo-structured vertical cavvity surface emission seemiconductors, lasing oon extremelyy higher-order
whispering--gallery moddes, dynamical chaotic m
modes, rotatinng radiation patterns, linnear and nonnlinear surfacce
modes, and cavity solitoons are demoonstrated in eexperiments aand simulatioons, respectivvely. Especiaally, we repoort
experimentaally the geneeration of sttationary creescent surfacce solitons ppinged to thee boundary, with a shappe
similar to Barchan
B
sandd dunes. Withhout any couunterparts in the linear lim
mit, the expeerimental obsservations annd
the simulatiion results prrovide an altternative but effective appproach to coontrol lasing characteristiics and access
optical surfa
face modes inn semiconduuctor lasers. As electronss localized att crystalline surfaces knoown as Tamm
m
and Shockleey states, opttical surface waves woulld provide a link in the rrelating classsical and quaantum regimees
for nonlineaar systems. M
Moreover, a thresholdlesss crescent wave
w
is propoosed by breaaking the sym
mmetry in thhe
surface struccture.
Fig. 1: Micro-structtured
Verticaal Cavity Surrface Emissioon Lasers (VC
CSELs).
References
[1] Tsin-Dongg Lee, Chih-Yaoo Chen, YuanYaao Lin, Ming-C
Chiu Chou, Te-hho Wu, and Rayy-Kuang Lee, "S
Surface-structure-assisted chaottic
mode lasingg in vertical cavvity surface emission lasers," P
Phys. Rev. Lett.. 101, 084101 (22008).
[2] Yuan Yao Lin, Chih-Yao Chen, Wei Chiien, Jin-Shan Pan, Tsin-Dong Lee, and Ray-K
Kuang Lee, "Ennhanced directioonal lasing by thhe
Lett. 94, 2211122 (2009).
interferencee between stablee and unstable pperiodic orbits,"" Appl. Phys. L
[3] Ching-Jen Cheng, YuanY
Yao Lin, Chih-Y
Yao Chen, Tsin--Dong Lee, andd Ray-Kuang Leee, "Lasing on hhigher-azimuthaal-order modes in
vertical cavvity surface emittting lasers at rooom temperaturre," Appl. Physs. B 97, 619 (2009).
58
[4] Wen-Xing Yang, Yuan-Yao Lin, Tsin-Dong Lee, Ray-Kuang Lee, and Yuri S. Kivshar, "Nonlinear localized modes in bandgap
microcavities," Opt. Lett. 35, 3207 (2010).
[5] Chandroth P. Jisha, YuanYao Lin, Tsin-Dong Lee, and Ray-Kuang Lee, "Crescent waves in optical cavities," Phys. Rev. Lett. 107,
183902 (2011).
Biography
Ray-Kuang Lee received his BS degree from the department of Electrical Engineering of the National Taiwan
University (EE/NTU) in 1993, and his MS and PhD degrees from the Institute of Electro-Optical Engineering of
the National Chiao Tung University (IEO/NCTU), in 1999 and 2004 respectively. Then he joined the Institute of
Photonics Technologies of the National Tsing Hua University (IPT/NTHU) as a faculty member at Aug. 2005,
where he established the theoretical optics group dedicated to the establishment of theory for optical solitons
and vortices in nonlinear photonic crystals, slow-light optics, Bose-Einstein condensates, quantum memory, and
optical device syntheses. Currently, he is an adjunct Professor of the department of physics of the National
Tsing Hua University. Dr. Lee’s research was recognized as an interdisciplinary work to the societies from
theoretical physics, applied photonics, to laser engineering, and due to his contributions, he received the Junior
Research Investigators Award from Academic Sinica, Taiwan (2012), the Wu Ta You Memorial Award from the
National Science Council, Taiwan (2011), the Outstanding Young Electrical Engineering Award from the
Chinese Institute of Electrical Engineering (2010), the Young Theoretical Physician Award from the National
Center for Theoretical Science, Taiwan (2010), the Young Optical Engineer Award from the Optical
Engineering Society of ROC (2009), the Y. Z. Hsu Scientific Paper Award from the Far Eastern Y. Z. Hsu
Science and Technology Memorial Foundation (2010), and the Exploration Research Award from the Pan Wen
Yuan Foundation (2009). He has published over 50 technical journal papers, and his work "Quantum Phase
Transitions of Light for Two-level Atoms," selected as one of “Optics in 2008” by the Optical Society of
America (OSA).
59
Excitability in Vertical-Cavity Surface-Emitting Lasers
subject to Orthogonal Optical Injection
P. Pérez1,2 , L. Pesquera1 and A. Valle1,*
1
Instituto de Física de Cantabria, CSIC-Universidad de Cantabria, Avda. Los Castros s/n, Santander, Spain
Departamento de Física Moderna, Facultad de Ciencias, Universidad de Cantabria, Avda. Los Castros s/n, Santander, Spain
*valle@ifca.unican.es
2
Abstract Our calculations show that self-pulsations, excitability and polarized rogue waves are obtained in
vertical-cavity surface-emitting lasers when they are subject to orthogonal optical injection.
Optical injection can induce rich nonlinear dynamics in the light emitted by Vertical-Cavity SurfaceEmitting Lasers (VCSELs). In contrast with edge-emitter lasers VCSELs have an extra degree of freedom
associated to the polarization of light. An example of nonlinear polarization dynamics has been recently
observed in 1550 nm wavelength VCSELs subject to orthogonal optical injection1,2. Polarization switching,
bistability, period doubling and irregular dynamics for both linear polarizations of the VCSEL were observed
before injection locking was achieved. Pulses observed in the irregular regime are similar to those resulting from
excitability in optically injected quantum-well and quantum dot edge emitting semiconductor lasers3. Rare
extreme pulses have been also observed in optically injected 980 nm wavelength VCSELs subject to parallel
optical injection4 and in 1550 nm wavelength VCSELs subject to orthogonal optical injection5.
In this work we perform a theoretical study of the polarization-resolved nonlinear dynamics of single-mode
linearly polarized VCSELs when subject to orthogonal optical injection. We use a set of rate equations based on
the spin-flip model. We show that self-pulsations appear in the total power and in both linear polarizations at
negative frequency detuning (frequency difference between the optical injection and the orthogonal polarization
of the VCSEL) when the injected power, Pin, is smaller but close to that required to achieve stable injection
locking, PIL. When Pin>PIL, excitable pulses can be triggered by perturbing laser variables above a certain
threshold level. Single, double, triple and multi-pulse behaviors are observed at different frequency detunings.
These excitable pulses are identical to the self-pulsations obtained when Pin<PIL. This behavior is observed both
in the deterministic case and when spontaneous emission noise is taken into account. Irregular multipulse
behavior is obtained in the deterministic case for specific frequency detunings and Pin<PIL. In this case the
parallel polarization is excited at the end of every pulse train. Train pulses are sporadic and the histogram of the
total power shows a long tail similar to those observed in rogue waves. Similar long-tailed histograms are
obtained for the powers of both polarizations. The characteristics of these theoretically obtained polarized rogue
waves obtained in VCSELs subject to orthogonal optical injection will be discussed in relation to rare extreme
pulses observed very recently in 1550 nm wavelength VCSELs subject to orthogonal optical injection5.
References
[1] A. Quirce, P. Pérez, A. Valle and L. Pesquera, JOSA B 28, 2765 (2011).
[2] J. P. Toomey et al, , Optics Express 20, 10256 (2012).
[3] B. Kelleher, C. Bonatto, G. Huyet and S.P. Hegarty, Phys. Rev. E 83, 026207 (2011).
[4] C. Bonatto et al, Phys. Rev. Lett, 107, 053901 (2011).
[5] K. Schires, A. Hurtado, I.D. Henning and M. J. Adams, Electron. Lett. 48, 872 (2012).
60