International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
The evaluation of laser diodes and gain media
Peter Blood
Department of Physics and Astronomy, Cardiff University,
Cardiff CF24 3YB, U.K
1. Basic analysis of threshold current data
Review of basic concepts of laser diodes: band diagram, threshold condition, gain-current characteristics.
Analysis of temperature dependence of threshold current, T 0, threshold as a function of cavity length.
Analysis of light current curves.
2. Device efficiency and Fermi level pinning
Definitions of internal and external differential efficiency, and overall efficiency. Relations between the
efficiencies and the measurement of efficiency. Interpretation of differential efficiency data, the role of
Fermi level pinning.
3. Methods for measurement of optical gain and intrinsic waveguide loss
Definitions of optical gain and absorption in quantum wells. Review and comparison of methods for
measurement gain from spontaneous emission, e.g., Hakki-Paoli and stripe length methods.
Measurement of the injection level and determination of gain-current relations. Comparisons between
experiment and theory.
4. Gain and absorption properties of quantum dots
Definitions of gain and absorption in quantum dots. Some simple numerical estimates and gain
saturation. Measurements. Independent or collective behaviour.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
Nanostructured Optoelectronic Materials and Devices
Connie J. Chang-Hasnain
Electrical Engineering and Computer Sciences Department
University of California, Berkeley, CA, 94720, USA
1. Ultraslow Light in Nanostructured Semiconductors
Part I: Physics and Materials
The past decades have witnessed an unprecedented information revolution. We are now able to process
hundreds of billions of computations per second and communicate terabits per second across thousands of
kilometers.
Optoelectronic technology played a pivotal role in activating this revolution. One key
fundamental challenge in information technology today remains to be: the processing, storing and buffering of
optical signals directly in optical format. As such, optical signals must be converted to electronic signals to
route, switch or be processed. This resulted in significant latencies and traffic congestions in current networks.
One of the grand challenges in optoelectronics is the ability to store an optical signal without converting it to an
electrical signal. Being able to keep the data in optical domain during the routing process is particularly of
interest, because it can greatly reduce the switching/routing delay, and the required power, complexity and size
of (electronic) routers. To this end, a controllable optical delay line can effectively function as an optical buffer
and the storage is proportional to the variability of the group velocity. Due to the delay time not being tunable, a
fixed fiber delay loop or waveguide resonator cannot serve the function of an optical buffer. On the other hand,
if we control the group velocity of light, we can generate a variable time delay. The capacity of buffering is
directly proportional to the variability of the light velocity. Such approach has received wide interests recently.
The application of a semiconductor optical buffer is not limited to all-optical routing. It can enable technologies
such as ultra-low Vpi modulators, true-time delay elements in microwave photonics, ultra-compact and low
power level nonlinear optical components, optical signal processing, and quantum information processing.
In semiconductors, slow-light via electromagnetically induced transparency (EIT) has been predicted in
quantum dot (QD) structures. Quantum dots exhibit delta-function like density of states and narrow
homogeneous linewidths on the order of meV~meV. A slow-down factor was predicted to be more than 1E5
with a uniform QD array at low temperature. Experimentally, slow-light via coherent population oscillation
(CPO) has also been investigated in semiconductors.
2. Ultraslow Light in Nanostructured Semiconductors
Part II: Novel Devices and Applications
Recently, we demonstrated for the first time in time-domain measurements that group velocity <200 m/sec and
slow down factor greater than 1.5E6 in GaAs/AlGaAs quantum wells (QWs) can be achieved at low
temperature. In this two-part talk, I will discuss the basic physics, material requirements, theoretical calculations
and review of recent experimental findings. Various potential applications will be discussed and the prospects
speculated.
3. MOCVD growth of III-V Nanowires
As the advancement of nanostructures progresses rapidly in a variety of application fields, extensive demands
for synthesizing nanostructures are growing. Among a wide range of nanostructures, one-dimensional
semiconductor nanostructures, such as nanowires (NWs), have been receiving considerable attentions with a
hope that only one NW, rather than an ensemble of many nanostructures, can be directly accessed through
external microscopic systems. Synthesis of group IV semiconductor NWs has been widely studied for many
years while group III-V semiconductor NWs appear to be still in their infancy, although many advantages
associated with physical characteristics and heterostructures of III-V semiconductors are readily recognized.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
In this talk, we will review recent progress made on III-V nanowires and discuss the optical and material
characteristics of III-V NWs.
4. Ultrahigh Speed Performance of Optical Injection-Locked VCSELs
I will discuss greatly enhanced high speed performance of directly modulated VCSELs under optical injection
locking. Injection locking of semiconductor lasers has been actively investigated recently. The locking
phenomenon happens when the wavelengths of the master laser and follower (slave) laser are very close to
identical. In this talk, we will review key recent results of injection-locked VCSELs with enhanced analog and
digital modulation performance. Due to the high Q of the VCSEL cavity, the injected photons are much more
effectively coupled into the follower laser (VCSEL). The resulting effects include an astoundingly large
increase of resonance frequency (from 7 GHz to >50 GHz), increase in modulation efficiency (10 dB) and spur
free dynamic range (>20 dB), and greatly reduced chirp under modulation.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
Connection between many-particle theory and
semiconductor laser engineering
Weng W. Chow
Sandia National Laboratories, Albuquerque, NM
87185-0601 USA.
1. Adaptation of general theory to analyze laser experiments
incorporation of bandstructure and resonator effects. k.p theory, Luttinger Hamiltonian, strained and unstrained
quantum well bandstructures. Numerical calculation of many-body gain and absorption spectra
2. Examples of interesting physics in semiconductor laser systems
Laser systems such as, VCSELs, wide-bandgap nitrides, type-II quantum wells and quantum dots. Many-body
effects in VCSELs, Quantum-confined Stark effects in wide-bandgap nitrides, charge separation effects in typeII lasers.
3. Examples of interesting physics in semiconductor laser systems
such as, VCSELs, wide-bandgap nitrides, type-II quantum wells and quantum dots. Many-body theory of gain
in quantum-dot structures. Dephasing effects in deep and shallow quantum dots. Quantum coherences in
semiconductor quantum dots.
4. Physics of high speed modulation in quantum-well and quantum-dot lasers
Nonequilibrium carrier effects. High speed modulation of quantum-well lasers and the effects of carrier-carrier
and carrier-phonon scatttering. Dynamical response of deep and shallow quantum-dot lasers. Effects of
nonequilibrium carrier populations.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
Modulated spectroscopy of semiconductor quantum dots
and Quantum dot single photon source
Jen-Inn Chyi
Optical Sciences Center and Department of Electrical Engineering
National Central University, Taiwan, China
1. Modulated spectroscopy of semiconductor quantum dots
(1) Introduction to modulation reflectance spectroscopy
(2) Electroreflectance spectroscopy (Electric field effects on InAs QDs: Quantum confined Stark effect
and permanent dipole moment; Strain reducing effects and/or strain-driven alloy decomposition)
(3) Electron-filling modulation reflectance spectroscopy (Experimental techniques and mechanism;
Carrier population and Coulomb charging effects; Electron and hole escapes from InAs QDs)
2. Quantum dot single photon source
(1)
(2)
(3)
(4)
(5)
(6)
Introduction
Device fabrication
Single quantum dot spectroscopy
Detection of anti-bunched single photons
Auto- and cross-correlation of exciton emissions
Photonic crystal single photon source
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
Optical microcavities and theoretical modeling of their
properties
Yong-Zhen Huang
State Key Lab on Integrated Optoelectronics, Institute of semiconductors
Chinese Academy of Sciences, PO Box 912, Beijing 100083, China
1. Optical Microcavities and their mode analysis
An introduction to optical microcavity, and discuss the analytical solutions of mode field distributions and
mode wavelengths for 2D microdisk, equilateral triangle resonator, and square resonators. Detailed
comparison with experimental results, mode symmetric characteristics based on group theory will also be
provided.
2. FDTD simulation of microcavity resonator
An introduction to the FDTD technique, Pade approximation to transform the time-series output of FDTD to
field spectrum and to obtain mode frequency and quality factor, 3D FDTD simulation for microdisk and square
resonator, and the application of Pade approximation to the simulation of photonic crystals.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
Basics of MBE growth and in-situ monitoring
Shane Johnson and Yong-Hang Zhang
Arizona State University, USA
This lecture will discuss the fundamentals of MBE growth mechanism and numerous in-situ monitoring
techniques such as Reflection High Energy Electron Diffraction (RHEED) and Diffused Reflectance
Spectroscopy (DRS).
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
Many particle theory of semiconductor nanostructures
Stephan W. Koch
Department of Physics and Materials Sciences Center
Philipps University Marburg, Renthof 5
35032 Marburg, Germany
1. General theory (2nd quantization, free particle results)
This lecture presents the theoretical background needed to understand the microscopic theory of the semiconductorlaser gain medium. The formalism of second quantization is introduced and the semiconductor gain is computed for
non-interacting carriers in 0, 1, 2, and 3 dimensions.
2.
Semiconductor Bloch eqs. and absorption and gain
In this lecture we include the important Coulomb interaction effects and derive the semiconductor Bloch equations
for the laser medium. Examples of gain and absorption spectra are discussed showing the effects of bandgap
renormalization, Coulomb enhancement, and the laser lineshape.
3. Luminescence in semiconductor nanostructures
Luminescence is the spontaneous emission of photons such that the systematic analysis requires the quantization of
the light field. We outline the derivation of the 'semiconductor luminescence equations' and discuss spontaneous
emission and other quantum optical effects in semiconductors.
4. Semiconductor nanostructures in spatially structured dielectric environments
In this lecture we discuss the modeling of semiconductor quantum wells, wires and/or dots, which are inside or close
to spatially structured dielectric media. We show that the structuring leads to modifications of the electromagnetic
field distribution and the Coulomb interaction potential between charge carriers. It is demonstrated that these effects
can be used to optimize gain in photonic bandege lasers. Furthermore, they allow us to generate excitonic
wavepackets and to obtain strong light-matter coupling for quantum dots in properly designed microcavities.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
DFB semiconductor lasers and integrated devices
Yi Luo
State Key Lab on Integrated Optoelectronics, Department of Electrical and Electronic Engineering
Tsinghua University, Beijing 100083, China
1. DFB lasers, theory and fabrication technology
2. High speed electroabsorption modulators and modulator integrated device, design, fabrication, and
measurement
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
Nanophotonics and Nanolasers
Cun-Zheng Ning
Center for Nanotechnology, NASA Ames Research Center, Moffett Field, CA 94035, USA
cning@arc.nasa.gov
The lectures will cover a new class of semiconductor nanostructures, namely nanowires made of
various semiconductors. Unlike typical planar nanostructures such as quantum wells, wires and dots,
these structures are typically surrounded by air or vacuum. From electronic point of view, electrons
are confined by infinite potential, while from optical point of view, strong mode confinement exists
because of the large refractive index difference between semiconductor and air. Strong electronic and
optical confinement leads to a serious of interesting properties of nanowires. The four lectures will
cover various aspects of such nanowires as outlined in the following:
1. Nanowire based nanodevices
This is an introductory lecture about nanowire nanophotonics. We will introduce some basic
properties of semiconductor nanowires first. We will then present a summary overview of various
nano-objects grown by tip-led chemical synthesis. The purpose is to give the participants an overall
feeling about what kinds of amazingly complicated and delicate nano-objects can be synthesized by
this tip-led growth technique and what photonic applications are possible with these structures. The
emphasis will be on nanowires as nanolasers, LEDs, detectors, and information processing units, and
waveguides.
2. Nanowire as waveguides
Whether used as lasers or waveguides, the waveguiding properties of nanowires are of great
importance. Some of the basic properties of a cylindrical waveguide such as the modes and
dispersion relations are century-old results, while others are results of recent investigations, such as
how a tightly guided wave is transmitted and reflected by facets, whose diameter is smaller than or
comparable to the wavelengths involved. In addition to reviewing the classical results of a cylindrical
waveguide as applied to nanowires, we will show how the reflection and transmission of strongly
guided modes at nanowire facets differ from the typical Fabry-Perot situation. We will also learn the
consequences of these differences for nanolasers or nano-waveguides.
3. Nanowire as nanolasers
There are mainly two aspects of nanowires that make lasers made of such wires very significantly
different from the usual semiconductor lasers based on planar heterostructures. The first is that the
characteristic dimension of nanowires is smaller or comparable to the wavelength of light in vacuum.
The second is that the difference in refractive indices of the core and cladding materials is much
larger for nanowires than for planar structures. Mainly because of these two important aspects, many
of laser properties need to be reconsidered for this new class of nanolasers. While weak waveguiding
leads to paraxial wave propagation in a typical planar semiconductor laser, strong waveguiding in a
nanowire leads to non-paraxial behavior. Such strong waveguiding also leads to strong coupling
between photons and electrons, leading to a confinement factor that is greater than unity. Many such
unique properties will be presented and compared with the more familiar planar semiconductor lasers.
4. Nanowire as LEDs
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
Optical dipoles in a nanowire can emit into modes that are guided by nanowires or into free-space modes. In a laser,
we wish to have all the dipole emission going into guided modes that would eventually become lasing modes, while
in a LED more emission into free-space modes is desired, leading to higher extraction efficiency. In either case, it is
important to understand how dipole emission in a nanowire is distributed between these two types of modes and
how such distribution changes with dipole orientation, wire diameter, and other parameters. In this lecture, we will
show how to compute dipole emission into these two types of modes; how the relative emission changes with wire
parameters, and how to use such distribution to design nanolasers or nanoLEDs.
Acknowledgement: Most of the contents of these lectures are the results of collaboration with Alex Maslov. I
appreciate his thoroughness in performing all the computations and his discussion on various aspects of nanowires.
Further Readings:
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J. Johnson et al, Single nanowire lasers, J. Phys. Chem., 105, 11387 (2001)
M. Huang et al., Room-temperature ultraviolet nanowire nanolasers, Science, 292, 1897(2001)
X. Duan et al., Single-nanowire electrically driven lasers, Nature, 421, 241 (2003)
H. Yan et a., ZnO nanoribbon microcavity lasers, Adv. Mater., 15, 1907 (2003)
J. Johnson et al., Optical cavity effects in ZnO nanowire lasers and waveguides, J. Phys. Chem., B107,
8816(2003)
A.V. Maslov and C.Z. Ning, Reflection of guided modes in a semiconductor nanowire laser, Appl. Phys.
Lett., 83, 1237(2003)
A.V. Maslov and C.Z. Ning, Far-field emission of a semiconductor nanowire laser, Opt. Lett., 29,
572(2004)
A.V. Maslov and C.Z. Ning, Modal gain in a semiconductor nanowire laser with anisotropic
bandstructure, IEEE J. Quant. Electron., 40, 1389(2004)
W.I. Park et al., Metalorganic vapor-phase epitaxial growth of vertically well-aligned ZnO nanorods, Appl.
Phys. Lett., 80, 4232(2002)
H. Kim et al., Nanoscale ultraviolet light emitting diodes using wide bandgap gallium nitride nanorods,
Adv. Mater., 15, 567(2003)
X. Wang et al., Large scale hexagonal-patterned growth of aligned ZnO nanorods for nanooptoelectronics
and nanosensor arrays, Nano Lett., 4, 423(2004)
M.S. Gudiksen et al., Growth of nanowire superlattice structures for nanoscale photonics and electronics,
Nature, 415, 617 (2002)
M. Law et al, Nanoribbon waveguides for subwavelength photonics integration, Sience, 305, 1269(2004)
J. Johnson et al, Ultrafast dynamics in single ZnO nanowire and nanoribbon lasers, Nano Lett., 4,
197(2004)
A. Maslov, M.I. Bakunov, and C.Z. Ning, “Optical emission of semiconductor nanowire emission into
guided modes and free space”, submitted to J. Appl. Phys.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
The physics of semiconductors for solid state lighting
Fernando Ponce
Arizona State University, USA
1. The physics of solid state lighting
(a) Evolution of lighting technologies
(b) Light emitting diodes
(c) The nitride semiconductors
(d) Producing white light illumination
(e) InGaN alloys
(f) Nature of InGaN quantum wells
(g) The potential of ZnO in solid state lighting applications
2. Applications of wide gap semiconductors
(a) Effect of microstructure on the internal quantum efficiency of LEDs
(b) Understanding device design effect on internal quantum efficiency.
(c) Visible LED applications
(d) UV LED applications
(e) Deep UV applications
(f) High resolution DVDs, laser printers, and medical applications
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
GaN materials and devices
Hui Yang
State Key Lab on Integrated Optoelectronics, Institute of semiconductors
Chinese Academy of Sciences, PO Box 912, Beijing 100083, China
1. MBE and MOCVD growth of GaN materials
Recent progress in the GaN growth study will be introduced. in-situ monitoring techniques such as optical
reflectance and wafer strain measurements will be discussed in connection with epitaxy mechanism and defects
control study.
2. GaN LED and Lasers Fundamental problems
Study of GaN LED and lasers, as well as their potential application in the future solid state light.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China
IR Semiconductor Lasers and Their Applications
Yong-Hang Zhang
Arizona State University, USA
1. VCSELs on GaAs substrate
This lecture will focus on the design of DBRs, QW structures for the active region, and current injection, and
optical mode control.
MBE growth of VCSELs will also be discussed. Experimental results of 850 nm, 1050
nm, and 1310 nm VCSELs will be presented and discussed.
2. Midwave IR lasers
This lecture will focus on the materials properties of (InGaAl)(AsSb) materials system and their MBE growths.
The design for laser active region using both type-I and type-II QW structures and possible choices of materials
for cladding layers will be also discussed.
3. Selected current optoelectronics research topics
This lecture will discuss several selected research frontiers in optoelectronics, including semiconductor optical
refrigeration and high power single mode VCSELs.
International Institute of Advanced Studies for Semiconductor Nanostructures and Optoelectronic Devices
3-10 August, 2005, Beijing, China