NCTU Electrophysics
Self-Mode-Locking Investigation of High-Power
Optically Pumped Semiconductor Laser
高功率光激發式半導體雷射之自鎖模研究
Advisor: Yung Fu Chen
Student: Yi Chun Lee
Date: 2010/07/09
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
Outline
1. Introduction
1.1 Background and Motivation
1.2 OPSL V.S DPSSL
1.3 OPSL Technology
2. OPSL Experimental Results
2.1 OPSL Parameter Optimized
2.2 Spontaneous Mode-Locking of OPSL
2.3 Theoretical Simulation
3. Summary and Future Work
Solid-State Laser Physics Lab.
Y.C. Lee
• Flashlamp Pumped Double Frequency Nd:YAG Laser ~532nm
NCTU Electrophysics
閉角型青光眼之小梁成型術
視網膜剝離、眼底止血
• Diode Pumped Double Frequency Nd:YVO4 Laser ~532nm
• Diode Laser ~810nm
青光眼治療、眼底光凝結手術
• Diode Pumped Double Frequency Nd:YAG Laser ~561nm
• Optical Pumped Semiconductor Laser ~577nm
眼底黃斑部病變
白內障手術
• Flashlamp Pumped Nd:YAG Laser ~1064nm
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
Optically Pumped Semiconductor Laser
Applications for OPSL
• Medical Field
• Life Science and Research
• Forensics
• Graphic Arts and Display
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
60fs
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
Strange Phenomenon in Time Domain
Reflector
Flash Lamp
Cr4+
Crystal
Polarizer
Output
Coupler
1064 nm
Nd:YAG Rod
Reflector
Mirror
Reflector
Flash lamp pumped passively Qswitched Nd:YAG laser
2 ns/div
Tr
Solid-State Laser Physics Lab.
Y.C. Lee
Strange Phenomenon in Time Domain
NCTU Electrophysics
Fiber-coupled LD @976 nm
cavity
HT@976 nm
HR@1030~1100 nm
Yb doped double-clad fiber PM; clad/core: Dia. 250/30 μm
(3m)
NA >0.46 /<0.06
FP filter 3x50 QWs
R~4%
Diode pumped passively Q-switched
Yb-doped fiber laser
Laser output
HR @ 1030~1100 nm
10 ns/div
Tr
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
Strange Phenomenon in Time Domain
Diode Pumped Diffusion-Bonded Nd:YVO4 Laser
808nm Laser Diode
Nd:YVO4
Crystal
Coupling Lens
Output
Coupler
1064nm
Cw-pumped diffusion-bonded Nd:YVO4 laser
100 ns/div
Tr
Cavity length：19 cm
Solid-State Laser Physics Lab.
2 ns/div
1 ns/div
Tr
Cavity length：45 cm
Y.C. Lee
NCTU Electrophysics
Self-Mode-Locked Nd:YVO4 Laser
Stable CW mode locking and short pulse width
Fiber coupled LD
Output coupler
200
(a)
(c)
200
ps/div
500
ns/div
pulse width ~ 23 ps
Intensity (a.u.)
150
100
39 ps
50
0
0
Solid-State Laser Physics Lab.
20
40
60
80
100
Delay time (ps)
12
120
140
Y.C. Lee
NCTU Electrophysics
INTRODUCTION
OPSL V.S DPSSL
DPSSL – Diode Pumped Solid State Laser
二極體激發式固態雷射
OPSL – Optically Pumped Semiconductor Laser
光激發式半導體雷射
 In 1980s, the progress in the growth technology of semiconductor
heterostructures developed the high-power diode laser pumped with a
solid gain medium is so called diode-pumped solid-state (DPSS) lasers.
 In 1997, M. Kuznetsov, F.Hakimi and A. Mooradian demonstrated the
first optically-pumped semiconductor laser (OPSL).
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
INTRODUCTION
OPSL V.S DPSSL
 The Mechanism of Stimulated Emission
- Four-Level System in Solid-State Laser and
Semiconductor Laser
△Ec
Eg
Eg
well
barrier
△Ev
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
INTRODUCTION
OPSL
OPSL V.S DPSSL
V.S
DPSSL
Diode Pumped Solid State Laser
Optically Pumped Semiconductor Laser
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
INTRODUCTION
OPSL Technology
• Semiconductor as Gain Medium
- Substrate
- Quantum Well
- Bragg Mirror
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
INTRODUCTION

OPSL Technology
GaAs substrate based
AlGaAs (800-870nm)
InGaAs (870-1150nm)
GaInNAs (1.1-1.5μm)

InP substrate based
Wavelength＞1.3μm
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
INTRODUCTION
OPSL Technology
• The Length of Quantum Well would be
designed as 1/2 laser wavelength
Active region
• Laser Wavelength would slightly shifted
according to quantum well design.
2.5
2.5
2
1  sin( x)
2
1  sin( x)
1
Energy
2.5
2.5
2
1.5
0.5 0.5
2.5
Laser optical standing wave
2.5
2
1
0
1
2
Multi-layer
Substrate mirrors (DBRs)
3
4
5
6
7
1  sin( x)
1.5
2

2
1.5
1.5
1
0.5 0.5
8
1
1
x
30 periods
2
1
1
Cap layer
Substrate
0.5 0.5
9
0
10 1
10
2
3
4
5
6
x
7
8
1
1
9
0
10
1
2
3
10
λ/2
4
5
6
7
8
9
x
…..
10
…..
10
Cap layer
 sin( x) 
2
Quantum wells
x
Pumping absorbing region
 0.5
Surface barrier
0
Semiconductor
Solid-State Laser Physics Lab.
Fig4.1.2 Bandgap diagram and operation principle of the OP-VECSEL
x
21.9
air
Y.C. Lee
NCTU Electrophysics
Outline
1. Introduction
1.1 Background and Motivation
1.2 OPSL V.S DPSSL
1.3 OPSL Technology
2. OPSL Experimental Results
2.1 OPSL Parameter Optimized
2.2 Spontaneous Mode-Locking of OPSL
2.3 Theoretical Simulation
3. Summary and Future Work
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
OPSL Optimized
Pumping Source
Semiconductor Gain Medium
1060 nm
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
OPSL Optimized
OPSL Optimized by using
• Different Radius of Output Coupler
• Cavity Length
Semiconductor
Gain Medium
Output
Coupler
High speed
photo-detector
Laser Diode
1060 nm
Focusing lens
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
OPSL Optimized
• Different Radius of OC and Cavity Length.
10
6
Cavity Length 50mm
4
2
0
10
15
Cavity Length 25 mm
8
Cavity Length 50 mm
Cavity Length 100 mm
8
Average Output Power (W)
Cavity Length 30mm
Average Output Power (W)
Average Output Power (W)
ROC = 250mm
ROC = 50mm
Cavity
Length ~7.4W
= 25mm, Max Power ~7.8W
Cavity Length = 30mm,
Max=Power
ROC
250mm
Cavity
Length ~7.03W
= 50mm, Max Power ~8.0W
Cavity Length ~ 50mm,
Max Power
Cavity
Length = 50mm,ROC
Max=Power
~8.0W
2000mm
Cavity Length = 100mm, Max Power ~ 7.8W
Cavity Length = 25mm, Max Power ~6.8W
8
Cavity Length = 50mm, Max Power ~6.7W
6
4
2
20
25
30
Pumped Current (A)
0
12
Solid-State Laser Physics Lab.
14
16
18
20
22
Cavity Length 50 mm
Cavity Length 25 mm
6
4
2
0
24
12 (A)14
Pumped Current
26
28
16
30
18
20
22
24
Pumped Current (A)
26
28
30
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
Digital oscilloscope
Semiconductor
Gain Medium
Output
Coupler
Laser Diode
1060 nm
Focusing lens
Power Optimized
5ns/div
Mode-Lock Optimized
5ns/div
High speed
photo-detector
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
ROC = 250mm
Cavity Length ~ 250mm
IP Curve of Mode Locking for 25cm Cavity Length
IP Curve of Power Optimized for 25cm Cavity Length
1.4
6
Specturm of Mode-Locking
Spectrum of Power Optimized
1.2
Intensity (a.u.)
Average Output Power (W)
8
4
2
1.0
0.8
0.6
0.4
0.2
0.0
1058
0
4
6
8
10
12
14
16
Pump power (W)
18
20
22
1059
1060
1061
1062
Wavelength (nm)
1063
1064
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
ROC = 250mm
Cavity Length ~ 250mm
Power Optimized
5ns/div
Solid-State Laser Physics Lab.
Mode-Lock Optimized
5ns/div
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
ROC = 250mm
Cavity Length = 187mm
IP Curve of Mode Lock Optimized for 18.75cm(3:1) Cavity Length
IP Curve of PowerOptimized for 18.75cm(3:1) Cavity Length
1.4
Specturm of Mode-Locking
Spectrum of Power Optimized
6
1.2
Intensity (a.u.)
Average Output Power (W)
8
4
1.0
0.8
0.6
0.4
2
0.2
0.0
1058
0
4
6
8
10
12
14
16
Pump power (W)
18
20
22
1059
1060
1061
1062
Wavelength (nm)
1063
1064
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
ROC = 250mm
Cavity Length = 187mm
Power Optimized
5ns/div
Solid-State Laser Physics Lab.
Mode-Lock Optimized
5ns/div
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
ROC = 250mm
Cavity Length = 125mm
IP Curve of Mode Lock Optimized for 12.5cm(4:1) Cavity Length
IP Curve of Power Optimized for 12.5cm(4:1) Cavity Length
6
1.4
5
Spectrum of Mode-Locking
Spectrum of Power Optimized
1.2
4
Intensity (a.u.)
Average Output Power (W)
7
3
2
1.0
0.8
0.6
0.4
1
0.2
0
0.0
1058
4
6
8
10
12
14
16
Pump Power (W)
18
20
22
1059
1060
1061
1062
Wavelength (nm)
1063
1064
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
ROC = 250mm
Cavity Length = 125mm
Power Optimized
2ns/div
Solid-State Laser Physics Lab.
Mode-Lock Optimized
2ns/div
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
ROC = 250mm
Cavity Length = 86mm
IP Curve of Mode Lock Optimized for 8.6cm(5:1) Cavity Length
IP Curve of Power Optimized for 8.6cm(5:1) Cavity Length
6
1.4
5
Specturm of Mode-Locking
Spectrum of Power Optimized
1.2
4
Intensity (a.u.)
Average Output Power (W)
7
3
2
1.0
0.8
0.6
0.4
1
0.2
0
0.0
1058
4
6
8
10
12
14
16
Pump power (W)
18
20
22
1059
1060
1061
1062
Wavelength (nm)
1063
1064
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
ROC = 250mm
Cavity Length = 86mm
Power Optimized
2ns/div
Solid-State Laser Physics Lab.
Mode-Lock Optimized
2ns/div
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
Power Optimized
2ns/div
ROC = 250mm
Cavity Length = 125mm
Average Output Power (W)
7
Mode Lock Optimized for 12.5cm(4:1) Cavity Length
Power Optimized for 12.5cm(4:1) Cavity Length
Fundamental Mode for 12.5cm(4:1) Cavity Length
6
Mode-Lock Optimized
2ns/div
5
4
3
2
Fundamental Mode
1
2ns/div
0
4
6
8
Solid-State Laser Physics Lab.
10
12
14
16
Pump Power (W)
18
20
22
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
• Scan the Beating to determine the distribution of
high-order mode.
Digital oscilloscope
Semiconductor
Gain Medium
Output
Coupler
High speed
photo-detector
Laser Diode
1060 nm
Focusing lens
Solid-State Laser Physics Lab.
Y.C. Lee
8
1
2ns/div
2ns/div
8
4
2ns/div
9
1
2
3
4
5
2ns/div
3
6
7
7
2ns/div
10
11
11
2ns/div
6
2ns/div
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spectral power density (dBm)
Spontaneous Mode-Locking of OPSL
-35
Transverse Frequency
-45
Longitudinal Frequency

-55
1
cos
g1 g 2
1
fT 
TR

-65

-75
1.6
3.2
4.8.
6.4.
8.0.
gi  1 
L
Ri
Frequency (GHz)
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Spontaneous Mode-Locking of OPSL
Fundamental Mode
8
Detected Point
1
High-Order Mode
Solid-State Laser Physics Lab.
3
4
6
7
11
High-Order Mode
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Theoretical Simulation
0
Eq ,m,n ( x, y, z, t ) 
e
m n
2   m! n!  ( z )
1
k q ,m,n 
q ,m ,n 

c
lcav
( x2  y 2 )
 (z)
2
 z 
 2 x   2 y  ikq ,m ,n ( x2 R(yz ) ) ikq ,m ,n ( z ct ) i (1 m n) tan1  zR 
e
H n 
H m 
e
e



 ( z)   ( z) 
2
2

l 
1 m  n
cos1 1  cav 
(q0  q) 

R 

q 0 表示縱向模態的指標， lcav 代表有效的共振腔長，R 為曲率半徑。
M 1
M
m, n
E
Solid-State Laser Physics Lab.
( x, y, z, t )   Eq,m,n ( x, y, z, t )
q 0
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Theoretical Simulation
E
M
m,n
1 M
3 M
( x, y, z , t )  E ( x, y, z , t )  E0,1 ( x, y, z, t )  E1, 0 ( x, y, z, t )
2
10
Solid-State Laser Physics Lab.
M
0, 0
Y.C. Lee
NCTU Electrophysics
OPSL EXPERIMENTAL RESULTS
Theoretical Simulation
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
Experimental Results
1
2
3
Solid-State Laser Physics Lab.
2ns/div
2ns/div
2ns/div
Theoretical Simulation
1
2ns/div
2
2ns/div
3
2ns/div
Y.C. Lee
NCTU Electrophysics
2ns/div
4
5
6
7
Solid-State Laser Physics Lab.
2ns/div
2ns/div
2ns/div
4
2ns/div
5
2ns/div
6
2ns/div
7
2ns/div
Y.C. Lee
NCTU Electrophysics
8
2ns/div
8
2ns/div
9
2ns/div
9
2ns/div
10
2ns/div
10
2ns/div
11
Solid-State Laser Physics Lab.
2ns/div
11
2ns/div
Y.C. Lee
8
8
1
2ns/div
2ns/div
2ns/div
2ns/div
1
8
44
2ns/div
2ns/div
9
1
2
3
4
5
2ns/div
2ns/div
33
6
7
7
7
2ns/div
2ns/div
10
11
11
11
2ns/div
2ns/div
6
6
2ns/div
2ns/div
Y.C. Lee
NCTU Electrophysics
Outline
1. Introduction
1.1 Background and Motivation
1.2 OPSL V.S DPSSL
1.3 OPSL Technology
2. OPSL Experimental Results
2.1 OPSL Parameter Optimized
2.2 Spontaneous Mode-Locking of OPSL
2.3 Theoretical Simulation
3. Summary and Future Work
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
SUMMARY AND FUTURE WORK
Summary
 OPSL also discovered the spontaneous mode-locking phenomenon.
The beating of the mode-locking output pulse trains are observed of
transverse modes coupling.
Theoretical simulation is matched to experimental results.
5ns/div
Solid-State Laser Physics Lab.
5ns/div
Y.C. Lee
NCTU Electrophysics
SUMMARY AND FUTURE WORK
0/1
Future Work
1/1
1/2
1/3
2/3
1/4
2/5
1/5
1/6
2/7
2/9
3/11
Solid-State Laser Physics Lab.
3/8
3/10
4/11
3/5
3/7
5/13
5/12
4/9
4/7
3/4
5/8
5/7
4/6
Farey Tree
Y.C. Lee
NCTU Electrophysics
SUMMARY AND FUTURE WORK
Future Work
1:3
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
SUMMARY AND FUTURE WORK
Future Work
2ns/div
1:4
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
SUMMARY AND FUTURE WORK
Future Work
2:5
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
SUMMARY AND FUTURE WORK
Future Work
5:12
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
SUMMARY AND FUTURE WORK
Future Work
5ns/div
7:17
12:29
Solid-State Laser Physics Lab.
Y.C. Lee
NCTU Electrophysics
SUMMARY AND FUTURE WORK
Future Work
Digital oscilloscope
Semiconductor
Gain Medium
Output
Coupler
High speed
photo-detector
Laser Diode
1060 nm
Focusing lens
Solid-State Laser Physics Lab.
SESAM
Y.C. Lee
NCTU Electrophysics
Thanks for your attention!
Solid-State Laser Physics Lab.
Y.C. Lee