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SPIE Photonics West 2010 · spie.org/pw584 Return to Contents
Contents7597: Physics and Simulation of Optoelectronic Devices
XVIII . . . . . .585
7598: Optical Components and Materials VII . . . . . . . . . . .
. . . . . . . . . .605
7599: Organic Photonic Materials and Devices XII . . . . . . . .
. . . . . . . .622
7600: Ultrafast Phenomena in Semiconductors and Nanostructure
Materials XIV . . . . . . . . . . . . . . . . . . . . . . . . . . .
. .636
7601: Terahertz Technology and Applications III . . . . . . . .
. . . . . . . . . .653
7602: Gallium Nitride Materials and Devices V . . . . . . . . .
. . . . . . . . . . .658
7603: Oxide-based Materials and Devices . . . . . . . . . . . .
. . . . . . . . . . .684
7604: Integrated Optics: Devices, Materials, and Technologies
XIV . .697
7605: Optoelectronic Integrated Circuits XII . . . . . . . . . .
. . . . . . . . . . . .709
7606: Silicon Photonics V . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . .715
7607: Optoelectronic Interconnects and Component Integration X .
. .730
7608: Quantum Sensing and Nanophotonic Devices VII . . . . . . .
. . . . .741
7609: Photonic and Phononic Crystal Materials and Devices IX . .
. . .761
7610: Quantum Dots and Nanostructures: Synthesis,
Characterization, and Modeling VII . . . . . . . . . . . . . . . .
. . . . . . . .776
7611: Advances in Photonics of Quantum Computing, Memory, and
Communication III . . . . . . . . . . . . . . . . . . . . . . . . .
.785
7612: Advances in Slow and Fast Light III . . . . . . . . . . .
. . . . . . . . . . . . .790
7613: Complex Light and Optical Forces IV . . . . . . . . . . .
. . . . . . . . . . .794
7614: Laser Refrigeration of Solids III . . . . . . . . . . . .
. . . . . . . . . . . . . . .801
7615: Vertical-Cavity Surface-Emitting Lasers XIV . . . . . . .
. . . . . . . . .804
7616: Novel In-Plane Semiconductor Lasers IX . . . . . . . . . .
. . . . . . . . .810
7617: Light-Emitting Diodes: Materials, Devices, and
Applications for Solid State Lighting XIV . . . . . . . . . . . . .
. . . . . .825
7618: Emerging Liquid Crystal Technologies V . . . . . . . . . .
. . . . . . . . . .840
7619: Practical Holography XXIV: Materials and Applications . .
. . . . .850
7620: Broadband Access Communication Technologies IV . . . . . .
. . .859
7621: Optical Metro Networks and Short-Haul Systems II . . . . .
. . . . .862
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Conference 7597: Physics and Simulation of Optoelectronic
Devices XVIIIMonday-Thursday 25-28 January 2010 • Part of
Proceedings of SPIE Vol. 7597Physics and Simulation of
Optoelectronic Devices XVIII
7597-01, Session 1
Microscopic theory and numerical simulation of quantum well
solar cellsU. Aeberhard, Forschungszentrum Jülich GmbH
(Germany)
With the increasing utilization of quantum confinement effects
in photovoltaic devices through the use of low-dimensional
structures such as quantum wells, wires or dots, microscopic
theories start to be required for an accurate analysis and
simulation of the device characteristics. These quantum
photovoltaic devices are optoelectronic systems where optimization
of both the
optical transitions and the transport properties are essential
for an ideal device performance. One of the most advanced
theoretical approaches able to describe both quantum optics and
quantum transport in nanoscale devices is based on the Keldysh or
non-equilibrium Green’s function (NEGF) formalism. In the present
paper, the NEGF approach is adapted to cover the photovoltaic
regime of operation of bipolar quantum well diodes as prototypes of
quantum photovoltaic devices. A microscopic theory is developed
that describes the essential photovoltaic processes of
photogeneration, carrier relaxation, radiative recombination and
transport to carrier selective contacts. The theory is numerically
implemented using band structure models ranging from single-band
effective mass to multiband tight-binding approaches. Interactions
with photons and phonons are described perturbatively via
corresponding self-energies on the level of the self-consistent
Born approximation. Carrier injection is considered through contact
self energies representing open-system boundary conditions. The
optical properties follow from the dielectric function derived
within the same theoretical framework via the calculation of the
transverse interband polarization function. To illustrate the
capabilities of the approach, a variety of microscopic and
macroscopic device properties is determined from the numerically
computed Green’s functions for different configurations of single
and multiple quantum wells, such as the local density of states,
charge carrier density, dark- and photocurrent as well as spectra
for absorption and emission, besides key photovoltaic
characteristics like I-V curves and quantum efficiency.
7597-02, Session 1
Modelling and performance of quantum well solar cellsP.
Kailuweit, R. Kellenbenz, F. Dimroth, Fraunhofer-Institut für
Solare Energiesysteme (Germany)
Embedding quantum wells into the depletion zone of the
p-n-junction of a III/V solar cell offers an elegant way to
optimize the cell performance by extending the absorption range of
a solar cell beyond the bandgap of the host solar cell. A
predictive theoretical modelling is an important prerequisite for
solar cell design to save development cost and to understand the
physical processes of such a solar cell. Such a model, based on a
commercial TCAD system, will be presented for a quantum well solar
cell. We calculated the external quantum efficiency of a GaAs solar
cell with a stack of quantum wells embedded into it’s intrinsic
region. The model was then calibrated to the measurements of a real
quantum well solar cell to determine material dependent fitting
parameters. After this calibration the predictive capability of the
model was proved by simulation of a different sample, leaving all
fit parameters fix. Results of different parameter variations will
be presented which reveal the physical behaviour of such a solar
cell and define the frame conditions of quantum well solar cells
for use in applications.
7597-03, Session 1
Zonal efficiency limit calculation for nanostructured solar
cellsJ. Kupec, ETH Zürich (Switzerland); S. Yu, B. Witzigmann,
Univ. Kassel (Germany)
The famous Shockley-Queisser detailed balance calculation for
determining the efficiency limit of a multi-junction solar cell
with respect to the bandgap energies does not address the strong
local deviations of the optical power absorption for the case of a
nanostructured cell. Furthermore, the assumption of perfect
absorption of all incident light exceeding the bandgap energies
cannot be justified. We present a modified Shockley-Queisser
efficiency limit calculation for nanostructured photovoltaic
devices. It incorporates a rigorous wave optics calculation and
spatially resolved generation of electron-hole pairs.
We apply this method to a single-junction and dual-junction
InAs/InP nanowire array for the use in concentrator solar cells. We
investigate the efficiency limits regarding the arrangement of the
active regions within the wire. We evaluate the efficiency limit of
various radial and axial junction designs and highlight the
influence of the electromagnetic modal characteristics on the local
generation rate as well as the interplay between nanowire geometry,
arrangement of the active regions and the bandgap energies.
Our results indicate that in a nanowire array solar cell with
low volume fill factor the efficiency limit can approach the values
of planar thin-film devices. This observation indicates the
occurrence of micro-concentration and underlines the necessity of a
wave optics approach. The spatially and spectrally resolved
analysis shows that generation on the surface of the nanowires is
considerable particularly with regard to high energy photons.
Therefore, it is necessary to efficiently extract those carriers
for highest efficiency designs.
7597-04, Session 1
Higher limiting efficiencies for nanostructured solar cellsJ.
Adams, Imperial College London (United Kingdom); G. Hill, J. S.
Roberts, The Univ. of Sheffield (United Kingdom); K. W. Barnham, N.
J. Ekins-Daukes, Imperial College London (United Kingdom)
New higher limiting efficiencies have been predicted for solar
cells with low-dimensional absorbers. The strain-balanced quantum
well solar cell is a GaAs p-i-n cell containing
compressively-strained InGaAs quantum well (QW) layers. At the
operating bias, the predominant loss mechanism is via radiative
recombination from the QWs, however it has been found that the QWs
have a fundamental efficiency advantage over bulk material as they
radiate anisotropically. The effects of quantum confinement and
strain in the QWs lift the degeneracy of the heavy hole (HH) and
light hole (LH) valence bands. The HH band couples to emission
perpendicular to the QWs, and the LH band couples predominantly to
emission in the plane of the QWs. In compressively-strained QWs,
the HH transition becomes more probable, so radiative emission is
suppressed in the plane of the QWs. Fundamentally, emission need
only occur in the same direction as absorption, a situation which
can be engineered by adjusting the energetic valence band alignment
via strain. This leads to a higher detailed-balance limiting
efficiency than in previous calculations where emission was assumed
to be isotropic. We will present the results of detailed-balanced
efficiency modelling in the radiative limit for isotropic and
restricted emission, including the effects of back-reflectors such
as the angularly-dependent distributed Bragg reflector. We will
discuss what occurs for a more realistic scenario where radiative
recombination is not
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Conference 7597: Physics and Simulation of Optoelectronic
Devices XVIII
the only loss mechanism in the cell. We will also present
experimental evidence indicating anisotropic emission in devices
with highly-strained QWs.
7597-05, Session 1
FDTD simulation of metallic gratings for enhancement of
electromagnetic field by surface plasmon resonanceH. P. Paudel,
South Dakota State Univ. (United States); K. Bayat, Univ. of
Waterloo (Canada); M. F. Baroughi, South Dakota State Univ. (United
States); S. May, Univ. of South Dakota (United States); D. W.
Galipeau, South Dakota State Univ. (United States)
Enhancement of electromagnetic field by engineered metallic
nanostructure on the metal surface by exciting surface plasmon
polaritons is investigated. We employed 3D Finite-Difference Time
Domain (FDTD) method for simulation of gratings in visible and NIR
radiations. Surface plasmon resonance has potential application in
photonic circuit miniaturization, optical signal processing,
optical signal switching, optical data storage, biosensors and
absorption enhancement in solar cell. Electromagnetic near-field
enhancement by two-dimensional array of metallic gratings on metal
surface and their characterization by size, shape, period, lattice
types, radiation angles and wavelength were not investigated
previously. Rectangular and cylindrical protrusions of two
dimensional gold (and silver) arrays in square and triangular
lattice on gold (and silver) surface interfaced with dielectric
material of refractive index 1.49 (PMMA) were simulated. We found
that the cylindrical grating in square lattice has the maximum
enhancement by 10 times and 50 times at sharp edges, which is
predominantly due to excitation of surface plasmons by grating’s
localized plasmons. We showed that grating parameters such as
grating period, aspect ratio and grating height can be tuned for
excitation of surface plasmon polaritons for particular frequencies
of interest. Results also showed that triangular lattice grating
has the wider enhancement bandwidth than square lattice gratings
and grating height is the most sensitive parameters of field
enhancement. We got the identical result from another FDTD
simulation tool ‘Meep’. The same amount of enhancement is found
when the measured reflectance is substituted in analytical
expression of field enhancement derived from conservation of
energy. The investigation explored the novel way of enhancing field
above metal surface by tuning the geometric sizes of gratings.
7597-06, Session 2
Multi-exciton generation in solar cells (Keynote Presentation)A.
Zunger, National Renewable Energy Lab. (United States)
Abstract not yet in.
7597-07, Session 2
Vitual single-crystalline GaAs photovoltaics on flexible metal
substratesA. Freundlich, V. Selvamanickam, Univ. of Houston (United
States)
Integration of III-V semiconductors with inexpensive flexible
substrates is a desirable feature to many opto-electronic
applications. In particular combining the unsurpassed performance
of GaAs based multi-junction technologies with conventional roll to
roll processing standards of thin film industry could lead to
paradigm-shifting reduction of the cost of solar electricity.
Here we report the fabrication of single crystalline GaAs
epilayers
on thin (50 microns) flexible polycrystalline metallic
substrates by molecular beam epitaxy (MBE). The flexible
poly-crystalline Ni-based substrates were coated with an
oxide-ceramic epitaxial buffer, adapted from a previously developed
structure for high Tc superconductor wire technology, followed by a
very thin (
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contribute considerably to the optimization of these devices. In
this work we present an electrical model to simulate DSCs based on
a Finite Element Method as an extension of TiberCAD code. The CAD
allows to calculate steady-state properties and ideal IV
characteristics of the cell shaping 1,2 and 3D meshes of the
device. The model handles all the charge carriers (cation, iodide,
triiodide, electron) coupled to Poisson equation on the same
footing within drift-diffusion equations. Recombination processes
using mass law equation at the oxide/electrolyte interface and
photogeneration of electrons in the oxide are included in the
model. The aim of this work is to investigate the different
performances of the cell by changing not only the topology of the
oxide region, but also the position of the electrodes, cathode and
photoanode, in order to optimize the cell characteristics.
7597-10, Session 3
Simulation and design of core-shell GaN nanowire LEDsB. J.
Connors, M. Povolotskyi, R. Hicks, B. Klein, Georgia Institute of
Technology (United States)
The high crystalline quality, large junction surface area, and
insensitivity to c-axis oriented polarization fields make
core-shell doped GaN nanowire p-n junctions exciting prospects for
use as LEDs. The LED external efficiency depends upon the spatial
distribution of optical recombination within the device, which may
be controlled through the use of radial heterojunctions, such as
quantum wells and electron blocking layers. In this work, we
explore the impact of an axially varying doping profile on the
spatial distribution of optical recombination in a GaN nanowire
LED.
The numerical simulation of the nanowire LED is carried out
using the TiberCAD simulation package. This package provides a
finite-element-based solution to the drift-diffusion model of a
nanowire. Simulations of core-shell nanowire LEDs are performed
with various doping profiles to produce variations in the optical
recombination distribution throughout the device.
In a core-shell device with a uniformly doped n-type core, the
current density tends to travel primarily along the core, as the
mobility of electrons is much greater than that of holes in GaN
devices. The optical recombination is concentrated beneath the
p-contact, where most of the current crosses the p-n junction. By
properly setting a tapered doping profile in the n-type core, it is
possible to increase the uniformity of the optical recombination
along the junction. In certain geometries this will increase the
extraction efficiency of the nanowire LED.
7597-11, Session 3
Modelling of AlN/GaN superlattices for integration in near-UV
distributed Bragg reflectorsA. Zorila, J. Jacquet, Supélec LMOPS
(France); A. Ougazzaden, Georgia Institute of Technology (France);
F. Genty, Supélec LMOPS (France)
One of the main problem for the realization of high reflectivity
GaN-based Bragg mirrors operating in the UV and near-UV wavelength
range is to limit the crack formation due to the lattice mismatch
between the different nitride compounds while keeping a large
refractive index contrast. In this system, the highest index
contrast is obtain between AlN and GaN but these compounds exhibit
a lattice mismatch as high as 2.4 %. Recent works have demonstrated
that the introduction of several AlN/GaN superlattices (SLs) in a
classical AlN/GaN quarterwavelength layers stacking strongly
improved the crystalline quality and thus the optical properties of
such a mirror. In this work, we have studied several AlN/GaN SLs
for their use directly as low index material in a Bragg mirror.
Such a configuration should allow to combine the limitation of
cracks by SLs with the improvement of the index contrast. First,
the band structure
of different AlN/GaN SLs was modelled and gap energies lower
than 3 eV could be found for several pseudo-alloys by choosing the
right relative thicknesses of AlN and GaN. Then, the optical
properties of the (AlN/GaN SLs)/GaN Bragg mirrors, centered at 400
nm and including these low gap SLs, were simulated showing that
high reflectivities (>99%) can be waited from these structures
with a relatively low number of pairs (< 20).
7597-12, Session 3
Optoelectronic and transport properties of nanocolumnar
InGaN/GaN quantum disk LEDsF. Sacconi, G. Penazzi, M. Auf der Maur,
A. Pecchia, A. Di Carlo, Univ. degli Studi di Roma Tor Vergata
(Italy)
Recent interest in III-nitride nanocolumn LEDs is due to their
promising features, such as a nearly dislocation-free growth.
Moreover, nanocolumns with a controlled variation of indium content
in the active region, the InGaN quantum disk (QD), are believed to
provide an high efficiency emission in the whole visible spectrum.
In this work we use the multi-scale software tool TiberCAD [1] to
study the transport and optical properties of a InGaN QD in a GaN
nanocolumn p-i-n diode structure, both with a macroscopical and an
atomistic approach. The aim of TiberCAD project is a device
simulator able to treat several different physical problems at the
relevant length scale, by applying each time the proper physical
models, ranging from macroscopical to atomistic representations.
TiberCAD simulator includes a mixed environment for FEM and
atomistic calculations. In such an environment, it is possible to
perform self-consistent FEM/tight-binding multiscale
calculations.
First, the strain and the drift diffusion equations for charge
transport are solved in the whole device, together with a k.p
multiband approximation for the computation of the quantum states
in the QD and its optical properties.
Then, in a multiscale paradigm, the atomistic structure of the
active region is generated, based on geometry and mesh
informations. Finally, the total (electric and polarization)
potential is projected on the on-site elements of the sp3s*d5
empirical tight-binding (ETB) Hamiltonian. On the other hand,
strain is included by applying displacements to the crystal lattice
and by scaling the tight-binding parameters accordingly.
Quantum states, electron and hole densities, and optical
recombination spectrum are computed within the InGaN QD by means of
ETB calculations; ETB particle densities are then projected up to
the macroscopic scale for a selfconsistent solution of the
drift-diffusion equations.
[1] M. Auf der Maur, M. Povolotskyi, F. Sacconi, and A. Di
Carlo, Superlatt. and Microstruct., 41, 5-6, (2007), p. 381-385
7597-13, Session 3
Numerical optimization of light-emitting diodes for
high-efficiency operationO. Heikkilä, J. Tulkki, Helsinki Univ. of
Technology (Finland)
We investigate how efficient the LEDs can ultimately be, how the
efficiency of LEDs is determined and how much of the efficiency is
sacrificed when high optical intensities are sought for using
extensive numerical simulations. The operation of LEDs is simulated
using a model that accounts for the macroscopic carrier transport,
photon extraction and heat exchange. The junction temperature is
solved self consistently along with the carrier transport
equations. The model is currently employed to simulate simple bulk
AlGaAs-GaAs double heterostructure LEDs which are expected to be
currently capable of the most efficient operation. The model is
used to calculate e.g. the external quantum efficiency (EQE) and
the wall plug efficiency to find the optimal operating range. Also
comparative calculations are made using simplified analytical
models. It will be shown that the optimal operating point is not
necessarily found at the maximum of EQE because of the
Conference 7597: Physics and Simulation of Optoelectronic
Devices XVIII
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SPIE Photonics West 2010 · spie.org/pw588 Return to Contents
contribution of lattice heat to the photon energy. Also the
plausibility of electro-luminescent cooling in realistic LED
structures is discussed. The efficiency droop limiting the high
power operation is analyzed to find the underlying mechanisms in
double heterojunction structures. The model is also used to predict
a limiting current at which an insufficiently cooled LED becomes
thermally unstable. Simple measures to increase the efficiency,
reduce the power consumption and lower the junction temperature of
LEDs are introduced based on the results, and experimental setups
for measuring various material and device parameters are
proposed.
7597-15, Session 4
Superconducting optoelectronicsI. Suemune, Hokkaido Univ.
(Japan)
Optoelectonics is expanding its application fields, such as
optical-fiber communications, displays, solid-state lightening and
so on. Superconductivity has been regarded as a basic research
field for some time but now it is also expanding the application
fields to mass-transport, superconducting magnet for NMR and MRI,
and highly sensitive SQUID magnetic-field sensors and so on.
However up to very recently, the two fields have very few
communications with each other. Now new trend is coming up: quantum
information communication and processing. Several candidates have
been proposed for quantum information processing of “Qubits”, and
one prominent candidate is superconducting qubits. They have
relatively long coherence time due to macroscopic quantum coherence
and have an advantage for future solid-state integration. These
“processing qubits” have to be converted into “messenger qubits” to
form networks for quantum information. The latter will rely on the
present optical-communication technology. For this purpose,
development of the interface technologies for the alliance of
photonics and superconductivity will open the new possibility. The
authors have proposed a photon-emitting LED combined with
superconducting electrodes, SQLED, which is expected to be a key
device to interface the two fields. This device is also expected to
generate on-demand entangled photon pairs. The main mechanism is
based on the coherent spatial extension of the Cooper-pair states
into the photon emitting active layer, which is expected to enhance
the oscillator strength of the radiative recombination processes by
the Cooper-pair involvement in the recombination processes. In this
talk, the fundamental principle of the SQLED operations and new
findings of LED light output enhancement and shortening of
radiative recombination lifetimes will be presented together with
its future prospect.
7597-16, Session 4
Properties of n-InAsSbP/n-InAs interfaceB. A. Matveev, A.
Ankundinov, N. Zotova, K. Sergey, T. L’vova, M. Remennyy, A.
Rybal’chenko, N. Stus’, Ioffe Physico-Technical Institute (Russian
Federation)
InAsSbP/InAs based heterostructures are quite commonly used for
LEDs and photodiodes (PDs) operating in the mid-IR spectral range
mostly at wavelengths around 3300 nm. The latter wavelength is
important for optical analyzers of the C - H gases, e.g. of the
methane gas or other hydrocarbons that have strong fundamental
absorption band at 3300 nm. Band gap discontinuities at an
InAsSbP/InAs interface are mentioned to affect the light source
performance and particularly the stimulated emission at low
temperatures. However no study of the band discontinuity values in
the InAsSbP/InAs structure was undertaken so far. In this work we
present experimental results permitting evaluation of the
n-InAsSbP/n-InAs interface discontinuities and show their impact on
the performance of double heterostructure
n-InAsSbP/n-InAs/p-InAsSbP LEDs and photodiodes operating at room
temperature at the wavelength of 3300 nm.
The report will focus on IR - image analysis, current - and
capacity - voltage integral characteristics, scanning Kelvin probe
microscopy (SKPM) measurements and surface potential distribution
as a function
of forward and reverse bias performed in flip-chip or (110) -
cleaved devices. The above measurements together with surface
photovoltage distribution analysis enabled us determining positions
and values of the potential barriers in n-InAsSbP/n-InAs/p-InAsSbP
heterostructures.
The obtained data will be discussed with the reference to
designing mid-IR LEDs with uniform current/emission distribution
over the active area and PDs with reduced capacity.
7597-17, Session 4
Band structure calculation of dilute-As GaNAs by first
principleX. Li, H. Tong, H. Zhao, N. Tansu, Lehigh Univ. (United
States)
Nitride semiconductors play important roles for light-emitting
diodes (LEDs) and lasers in visible spectrum. High-efficiency LEDs
and low-threshold lasers based on InGaN quantum wells in green
regime are challenging due to charge separation, high strain misfit
dislocation, and possible large interband Auger recombination.
Here, we investigate the band structure of the dilute-As GaNAs
alloys (0% up to 8% As) by employing First-Principle method, for
exploring new active materials in visible spectrum. Significant
studies have been carried out on understanding the band structures
of dilute-nitride GaNAs (up to 5% N) for near IR emission. In
contrast to that, very few studies have been carried out on
analyzing the band structure of the dilute-As GaNAs alloy, thus its
important parameter such as band offsets between individual
conduction bands and/or valence bands at the gamma point of the
Brillouin zone (BZ) remain unknown. The properties of the band
structures for the GaNAs alloys have fundamental impacts on the
development of these materials into advanced device applications.
The band structures of the dilute-As GaNAs were calculated by the
Density-Functional Theory that adopts the Generalized Gradient
Approximation, and the calculation routine is along
high-symmetrical k-points in the BZ. The incorporation of dilute-As
into the GaNAs alloy leads to significant decrease in the bandgap
of the material, which allows direct band gap transition covering
from 2.8eV (As-content of 3%) down to 1.8eV (As-content of 7%). The
First-Principle shows that the dilute-As GaNAs alloy as a candidate
for excellent active material for LEDs and lasers in visible
regime.
7597-18, Session 4
Lasing and gain characteristics in Ga(NAsP) heterostructures on
SiC. Lange, S. Chatterjee, W. W. Rühle, Philipps-Univ. Marburg
(Germany); N. Koukourakis, N. Gerhardt, M. Hofmann, Ruhr-Univ.
Bochum (Germany); S. Liebich, M. Zimprich, R. Fritz, B. Kunert, K.
Volz, W. Stolz, Philipps-Univ. Marburg (Germany)
The creation of a direct band-gap material on silicon is
envisioned to enable advanced optoelectronic integrated circuits
with drastically improved performance combining the advantage of
optical data processing with the well-established silicon
processing technology. However, the realization of a laser diode
based on Si remains a challenge to date due to the indirect nature
of its band structure. One possible solution is the integration of
standard direct band gap III/V laser material such as GaAs or InP
on Si-substrates. Still, the large lattice mismatch of these
materials to Si causes high densities of threading dislocations in
the epitaxial films, preventing any long-term stable lasing
operation of integrated III/V laser diodes. In order to avoid
dislocation formation, the novel direct band gap
Ga(NAsP)/GaP-material system has been introduced which exhibits
lasing up to room temperature for epitaxial growth on
GaP-substrates for both optical and electrical injection.
Here, we investigate the gain and lasing characteristics of a
Ga(NAsP)/(BGa)(AsP) multiple quantum-well laser structure grown by
metal-organic vapour-phase epitaxy on an exactly-oriented (001) Si
substrate. We observe lasing action after pulsed optical excitation
for various samples.
Conference 7597: Physics and Simulation of Optoelectronic
Devices XVIII
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The emission power shows a clear threshold behaviour as function
of excitation density at temperatures ranging from 10 K up to 125
K. Clear mode spectra are observed and an analysis with the
Hakki-Paoli method yields a lower limit for maximal modal gain of 5
cm-1.
7597-19, Session 4
Influence of disorder on photoluminescence dynamics of
Ga(AsBi)A. Chernikov, S. Chatterjee, C. Bückers, S. W. Koch,
Philipps-Univ. Marburg (Germany); S. Imhoff, A. Thränhardt,
Technische Univ. Chemnitz (Germany); X. Lu, The Univ. of British
Columbia (Canada); T. Tiedje, Univ. of Victoria (Canada); S.
Johnson, Arizona State Univ. (United States)
The design new long wavelength material on GaAs substrates with
the ability to produce telecom or even longer wavelengths on GaAs
substrates is a major task in todays development of novel alloyed
semiconductor materials. Recently, dilute Ga(AsBi) has been
proposed as a potential candidate for an such an emitter material
due to its giant bandgap bowing.
Here, we present time-resolved photoluminescence experiments on
a 30nm Ga(AsBi) epilayers as function of excitation flux and
lattice temperature. The sample contains a Bi fraction of about
4.5% and was grown by molecular beam epitaxy on semi-insulating 100
GaAs substrate. A 80MHz, 100fs Ti:sapphire oscillator centred at
1.55eV and 1.35eV is used for excitation above and below the GaAs
substrate band gap energy; a standard spectrometer and
streak-camera setup with a water-cooled S1 cathode yielding a
time-resolution of 2ps is used for detection. The peak of the near
band edge emission shifts from 1.13eV to 1.23eV as the excitation
flux is increased be more than two orders of magnitude at a lattice
temperature of 10K. This blue shift is a clear sign of disorder
present in the system. This is also supported by the low-energy
tail of the emission spectrum which is spectrally more flat than
the high-energy flank. The decay times increase across the emission
band indicating a complex interplay between carrier relaxation and
recombination. A pronounced S-shape is found for the emission peak
as function of lattice temperature yielding a disorder potential of
several 10’s of meV.
7597-20, Session 5
Carrier dynamics in ZnMgO studied by time-resolved
photoluminescenceA. Chernikov, M. Koch, S. Chatterjee, K. Volz, B.
Pasenow, S. W. Koch, Philipps-Univ. Marburg (Germany); P. J. Klar,
M. Eickhoff, B. K. Meyer, Justus-Liebig-Univ. Giessen (Germany); B.
Laumer, T. A. Wassner, M. Stutzmann, Technische Univ. München
(Germany)
A major step towards the development of ZnO-based UV emitters is
the development of quantum well structures. Typically, Zn1-xMgxO is
used as barrier material due to its similar in-plane lattice
parameter and considerable band offsets. Here, we investigate the
properties of different wurtzite Zn1-xMgxO epilayers with varying
Mg contents. All samples were grown by plasma-assisted molecular
beam epitaxy on c-plane sapphire substrates, using a MgO/ZnMgO
buffer .
We perform time-resolved photoluminescence experiments as
function of excitation flux and lattice temperature. A
frequency-tripled 80MHz, 100fs Ti:sapphire oscillator centred at
4.3eV is used for excitation; a standard streak camera setup
yielding a time-resolution of 800fs is used for detection.
The peak of the near band edge emission shifts from 3.38eV to
4.05eV as the Mg concentration is increased from x=0 to x=0.35 at a
lattice temperature of 10K. The decay times increase by more than
one order of magnitude as the Mg concentration increases indicating
stronger
localization. This is further supported by an increase of the
respective spectral linewidths.
Typically, a series of phonon replica is observed for all
samples. At low temperatures, the sample with x=0 (clearly) shows
replica of the near band-edge emission while the replica signatures
from bound excitons become more important as the Mg concentration
is increased.
The bound excitons are ionized as the lattice temperature is
increased revealing the zero phonon line as well as phonon replica
associated with the free exciton emission line similar to the
well-known ZnO material system.
7597-21, Session 5
Frequency modulation response of two-section quantum cascade
lasersE. Luzhansky, F. Choa, Univ. of Maryland Baltimore County
(United States)
Abstract: we describe the theory of frequency modulation (FM)
response of Quantum Cascade Lasers (DFB QCL). It includes cascading
effect on QCL’s maximum modulation frequency. Theory is enhanced
with description of FM response of two section Distributed Feedback
Laser (DFB) QCL. It is shown, that, in contrast to laser diodes,
the FM response of two section QCLs is independent of the optical
power. It can be optimized by correlation of two sections’
effective lengths and by controlling the relative difference of
their linewidth enhancement factors, . Utilization of model for the
single section DFB QCL and agreement with previous results is shown
as well.
7597-22, Session 5
Physical-random number generation using laser diodes’ inherent
noisesH. Nishimura, K. Doi, T. Ushiki, T. Sato, M. Ohkawa, Y.
Odaira, Niigata Univ. (Japan)
Random numbers can be classified as either pseudo- or
physical-random in character. This work demonstrates how laser
diodes’ inherent noise can be exploited for use in generating
physical-random numbers in the field of cryptography.
Pseudo-random numbers’ periodicity renders them inappropriate
for use in cryptographic applications, but, naturally-generated,
physical-random numbers have no calculable periodicity, thereby
making them ideally-suited to the task. Laser diodes naturally
produce a wideband “noise” signal that is believed to have
tremendous capacity and great promise, for the rapid generation of
physical-random numbers for use in cryptographic applications.
Because the character and shape of the laser diode’s oscillation
exert tremendous influence on the intensity and frequency noises,
we need to determine which noise is best suited for the generation
of fast physical-random numbers. To do this, we worked to identify
the frequency noises by observing the transmitted light intensity
through the frequency reference, and generated the physical-random
numbers using an analog-digital (A/D) converter that produces, for
example, 8-digits binary numbers from the detected laser
intensity.
In the initial stages of the experiment, we measured a laser
diode’s output, at a fast photo detector and generated
physical-random numbers using laser diode’s intensity noises. We
then identified and evaluated the binary-number-line’s statistical
properties. Because the frequency noise has higher frequency
components than the intensity noise has, our preliminary result
shows that fast physical-random numbers are obtainable, using the
laser diode’s frequency noise characteristic.
Conference 7597: Physics and Simulation of Optoelectronic
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SPIE Photonics West 2010 · spie.org/pw590 Return to Contents
7597-23, Session 5
Complex low energy gain switching pulse processing using a
highly nonlinear optical loop mirrorC. de Dios Fernandez, H. R.
Lamela, Univ. Carlos III de Madrid (Spain)
When it comes to obtaining short optical pulses from diode
lasers, Gain Switching (GS) shows as a direct and straightforward
technique. It is a compact source for frequency tunable, high
repetition rate, low-cost optical pulses in the picosecond range
that can be applied to Commercial Off the Shelf (COST) diode
lasers. Pulses from GS are widely used nowadays [1][2]. However,
their application in new fields is at times limited. The pulses
obtained have low power, an asymmetric shape and frequently present
a trailing substructure that forms pedestals [3]. Depending on the
laser technology considered, Fabry-Perot lasers, DFB [4] or VCSELs
[5], the pulses generated vary from hundreds of picosecond to tens
of picoseconds. Thus, improving the quality of GS pulses, due to
their complex structure, low power and long temporal width, is a
challenging task.
Nonlinear Optical Loop Mirrors (NOLM) are interferometric
nonlinear devices based on an optical fiber Sagnac configuration,
which are extensively used as part of optical communication systems
[6] and as pulse compression and shaping devices. They are
versatile and several studies have proposed different designs for
these loops [7][8]. Hence, they make good candidates for the
improvements of GS sources. However, as nonlinear devices, they
exhibit a power dependant behavior. Then, the performance of NOLM
is sensitive to the characteristics of the input pulse train. Also,
long loops and high input energies are often needed to obtain
compression or reshaping of the pulses. As a result, the
capabilities of NOLMs cannot be used directly on low quality
pulses, such as those obtained from GS diode lasers, without
preprocessing stages [9].
In this work, we study the improvement of complex low quality
pulses obtained from GS sources using a compact Highly Nonlinear
Optical Loop Mirror (HNOLM) based on a high speed Nonlinear
Semiconductor Optical Amplifier (NLSOA) and a Microstructured
Optical Fiber (MOF). The loop is compact, containing 20 m of
optical fiber and does not require any intermediate stage to
process the pulses. The capability of the HNOLM to improve the
pulse characteristics has been studied for several input energies
in this work. Finally, the pulse quality has been evaluated too
using the temporal pulse width, spectral width, pulse shape,
pedestals height and pedestal width. Results show that HNOLM
provides direct compression and pulse shaping for picosecond
complex pulses obtained from a DFB COTS laser operating within the
1550 nm window.
References:
[1] H. Shams, A. Kaszubowska-Anandarajah, P. Perry, and L.
Barry, “Demonstration and optimization of an optical impulse radio
ultrawideband distribution system using a gain-switched laser
transmitter,” Journal of Optical Networking, vol. 8, no. 2, pp.
179-187, 2008.
[2] H Liu, C. Gao, J. Tao, W. Zhao, and Y. Wang, “Compact
tunable high power picosecond source based on Yb-doped fiber
amplification of gain switch laser diode,” Optics Express, vol. 16,
no. 11, 2008.
[3] P. Vasil’ev, I.H. White, and J. Gowar, “Fast phenomena in
semiconductor lasers,” Rep. Prog. Phys., vol. 63, 2000.
[4] K. Otsubo et al., “Uncooled 25 Gbis/s direct modulation of
semi-isulating buried-heterostuctured 1.3 um AlGaInAs quantum-well
DFB lasers”,” Electronics Letters, vol. 44, pp. 631-633, 2008.
[5] M. Nakazawa, H. Hasegawa and Y. Oikawa, Student Member, IEEE
“10-GHz 8.7-ps Pulse Generation From a Single-Mode Gain-Switched
AlGaAs VCSEL at 850 nm” IEEE Photonics Technology Letters, vol. 19,
no. 16, 2007.
[6] S. Boscolo, S. K. Turitsyn, and K. J. Blow, “Nonlinear loop
mirror-based all-optical signal processing in fiber-optic
communications,” Optical Fiber Technology, vol. 14, pp. 299-316,
March 2008.
[7] S. Takamatsu, H. Watanabe, T. Matsuyama, H. Horinaka and K.
Wada,
“Pulse-shaping of gain-switched pulse from multimode laser diode
using fiber Sagnac interferometer,” Optics Express, vol. 16, no.
24, 2008.
[8] K. Smith, E.J. Greer, N.J. Doran, D.M. Bird, and K.H.
Cameron, “Pulse amplification and shaping using a nonlinear loop
mirror that incorporates a saturable gain,” Optics Express, vol.
17, no. 6, pp. 408-410, March 1992.
[9] Y. J. Chai, I. Y. Khrushchev, R. V. Penty, and I. H. White,
“Interferometric Noise Suppression by Means of
Dispersion-Imbalanced Loop Mirror Over a Wavelength Range of 28
nm,” IEEE Photonic Technology Letters, vol. 14, no. 3, 2002.
7597-24, Session 6
Quantum design and experimental realization of high-power
VECSELsS. W. Koch, Philipps Univ. Marburg (Germany)
Our micsrocsopic quantum theory is used to design VECSELs for
special emission wavelengths and/or high power output. The main
ingredients of the quantum design scheme are reviewed and examples
of realized structures and experimental results are shown.
This work is done in collaboration with J.V. Moloney, J. Hader,
Y. Kaneda et al. Tucson, W. Stolz, B. Kunert, S. Chatterjee, et
al., Marburg
7597-25, Session 6
Cavity design and heat management in vertical-external-cavity
surface-emitting lasers (VECSELs)T. Lu, Y. Kaneda, M. J.
Yarborough, College of Optical Sciences, The Univ. of Arizona
(United States); J. Hader, Nonlinear Control Strategies, Inc.
(United States); J. V. Moloney, College of Optical Sciences, The
Univ. of Arizona (United States) and Nonlinear Control Strategies
(United States); A. Chernikov, M. Koch, B. Kunert, W. Stolz, S.
Chatterjee, C. Bückers, S. W. Koch, Philipps-Univ. Marburg
(Germany)
Vertical-External-Cavity Surface-Emitting Lasers (VECSELs) or
semiconductor disk lasers in the infrared spectral range display a
highly desirable combination of high output power, good efficiency,
and good beam quality out of a small package. Additionally,
high-speed frequency-doubled semiconductor disk lasers have been
realized covering large parts of the visible spectrum, e.g., for
full-color laser projection or as laser guide-star systems. The
realization of high-power devices such as the latter requires a
careful interplay between cavity design and heat management.
We experimentally investigate a model high-power device. A
1040nm VECSEL is realized using the semiconductor chip and a
spherical output coupler in a linear cavity design. First, the
performance is investigated as function of the reflectance of the
output coupler. Next, we investigate the influence of the pump spot
profile on the lasers parameters. It is investigated by varying the
pump optics and their geometry, e.g., angle under which the pump is
incident and role of aberrations such as defocus or tilt, such that
the performance is optimized.
Different heat spreading and heat removal concepts in materials
such as copper and diamond are compared. The respective performance
is monitored under comparable high power pumping and cavity
conditions by recording the spectrally resolved emission and the
input-output characteristics. Finally, different cavity geometries,
their respective impact on the mode size at the active region and
the consequences for power scalability are discussed.
Conference 7597: Physics and Simulation of Optoelectronic
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TEL: +1 360 676 3290 · +1 888 504 8171 ·
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7597-26, Session 6
Ultrafast circular polarization oscillations in spin-polarized
vertical-cavity surface-emitting laser devicesN. C. Gerhardt, M.
Li, H. Jaehme, H. Soldat, M. R. Hofmann, Ruhr-Univ. Bochum
(Germany); T. Ackemann, Univ. of Strathclyde (United Kingdom)
The combination of spin injection with optical amplification in
spin-lasers offers new encouraging possibilities for future
devices. Here we investigate the room temperature spin, carrier and
polarization dynamics of electrically pumped vertical-cavity
surface-emitting lasers (VCSELs) on a picosecond time scale, after
injection of a small degree of spin polarization for the electron
band population. For this purpose, we apply a hybrid excitation
technique combining continuous-wave unpolarized electrical and
picosecond spin-polarized optical excitation of a commercial VCSEL
device. The experimental results demonstrate ultrafast circular
polarization oscillations due to spin injection with an oscillation
frequency of 11.6 GHz. The polarization dynamics are faster than
the intensity dynamics due to the relaxation oscillations. Even
more interesting, the circular polarization oscillations persist
for more than 5 ns after spin injection, which is much longer than
the spin-relaxation time in this device. We compare the
experimental results with theoretical calculations on the basis of
rate equation models for spin-polarized lasers in order to analyze
the complex interplay between birefringence, spin- and carrier
relaxation as a reason for the long persisting circular
polarization oscillations in spin-VCSELs. A detailed understanding
of the spin-dynamic mechanism of the polarization oscillations
offers the possibility for independent polarization and intensity
modulation in future spin-VCSEL devices.
7597-27, Session 6
Electro-optically modulated VCSELs and RCLEDsJ. A. Lott, V. A.
Shchukin, N. N. Ledentsov, VI Systems GmbH (Germany); T. D.
Germann, A. Strittmatter, A. Mutig, D. Bimberg, Technische Univ.
Berlin (Germany)
We present the design, simulation, operating principles, growth,
fabrication, and measured performance results of 850 nm-range
electro-optically modulated (EOM) vertical cavity surface emitting
lasers (VCSELs) and resonant cavity light emitting diodes (RCLEDs).
The device structures are grown in a well-controlled single
monolithic epitaxial growth step by both molecular beam epitaxy and
metal-organic vapor phase epitaxy and are produced via standard
large-volume micrometer-scale-device processing techniques. Finally
we discuss how to use this innovative approach for the realization
of high speed (> 10 Gb/s) optical signal modulation to enable
the next generation of low cost and extremely reliable short-reach
optical data communication systems.
7597-28, Session 7
Micro-diffraction lenses with subwavelength structures designed
by the genetic algorithmT. Shirakawa, Univ. of Tokyo (Japan); K. L.
Ishikawa, RIKEN (Japan); S. Suzuki, Y. Yamada, Ricoh Co., Ltd.
(Japan); H. Takahashi, Univ. of Tokyo (Japan)
Recent progress of nanotechnology has enabled the fabrication of
diffractive optical elements (DOEs) with subwavelength structures
(SWSs). However SWS DOEs can be designed neither by scalar
diffraction theory nor by Fourier optics. To solve this difficulty,
we have recently developed a design method based on the
finite-difference time-domain (FDTD) method and the genetic
algorithm (GA), called the
GA-FDTD method. In this study, we present the design of SWS
micro diffraction lenses with a 4 μm radius.
Maxwell’s equations are solved by the FDTD for a system with
axial symmetry with the perfectly matched layer absorbing boundary
condition. The relief structure and height of the lens are
optimized with the GA using binary coding. In consideration of
actual fabricability, the grating width is 100 nm at least and the
aspect ratio is 5 at most.
The optimized structure has more than twice as high focusing
ability at a wavelength of 660 nm as that previously reported based
on the binarization of the Fresnel lens, and turns out to be robust
against fabrication error. Its grating height (400 nm) is different
from that of the Fresnel lens (576 nm), and the relation between
the widths of neighboring gratings cannot be expressed in a simple
way. Furthermore, we have successfully designed a lens with equal
focal length at three different wavelengths (660, 532, and 445 nm).
The structures, which are not intuitive, are hard to deduce from
experiences. These results indicate the effectiveness of the
GA-FDTD method in the design of SWS DOEs.
7597-29, Session 7
LED integrated optical encoderL. Acevedo, M. P. Y. Desmulliez,
Heriot-Watt Univ. (United Kingdom)
The incoherent wave front emitted from a LED can be modelled by
analysing the diffraction produced by a 4 micron period grating
attached to the refractive glass sitting on top of the LED. Such a
configuration is used for optical encoding application [reference
needed, paper by John Carr, ESTC 2008.
In our application, the 460 microns diameter LED with an epitaxy
thickness of 3.066 um is used within a monolithically integrated
optical encoder. The incident light source from the LED is
impinging onto the index grating manufactured at the surface of the
substrate of the LED and further transmitted to a scale grating
with a diffraction order of +1 and -1. Surfaces to determine the
incidence irradiance (power/unit-area) impinging into the
photodetector placed 1 mm away, the emitted divergence radiance per
solid angle (power/steradian), and the diffractive flux allow us to
compare these optical outputs with those obtained experimentally.
Experimental data have been obtained by recording the power
incident on the tip of a 8 um core optical fiber as it scans across
the LED. Moreover, the theoretical model and the measured
Lambertian beam are compared to the output parameters of the LED
(2013 Farfield LED) as shown in Figures (1,2) and simulated source
in Figures (3, 4, 5) below.
The simulating environment determines the behaviour of the rays
of the light source in a Lambertian wavefront profile. It also
predicts the Talbot effect produced by the grating when the light
is propagated to the gratings of the optical encoder. Therefore by
analysing the geometric configuration of the system such as the
gratings period and pitch, the distance between LED and
photodetectors, can be optimised to reduce optical crosstalk and
increase output throughput
References
Optical Encoder Readhead Chip 078-1-4244-2814-4/08/$25.00@2008
IEEE
7597-30, Session 7
Study of propagation modes of bent waveguides and micro-ring
resonators by means of the aperiodic Fourier modal methodD. Bucci,
B. Martin, A. Morand, Institut de Microélectronique
Électromagnétisme et Photonique (France)
In the last years, several numerical methods have been studied
and applied to the analysis of high index contrast bent
waveguides.
Very often, the problem is treated by using a conformal mapping,
which
Conference 7597: Physics and Simulation of Optoelectronic
Devices XVIII
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SPIE Photonics West 2010 · spie.org/pw592 Return to Contents
translates the bending into an equivalent index profile.
In this article, we will discuss the implementation of a full
vectorial 2D mode solver by means of the Aperiodic Fourier Modal
Method, developed directly in cylindrical coordinates.
In the first part of our work, we will develop a shorthand
notation and the mathematical rules useful to describe the problem
in a matrix form. The search of propagation modes is then
reconducted to the search of eigenvectors of a matrix. We will at
first test our formulation in 1D with results given by the
conformal mapping technique.
In a second time, we will use the complete 2D solver to the
determination of the resonance frequencies and quality factors of
micro-ring resonators made on silicon surrounded by silica. These
characteristics are related to the real and imaginary part of the
propagation constants. By comparison with 3D-FDTD analysis, we will
show how our implementation can be used to accurately describe the
behavior of micro-rings having a bending radius as low as 1 μm.
This technique is general and can be applied on micro-rings having
an arbitrary cross-section and a quality factor comprised between
100 and 10000.
Perspectives of this work include the study of the propagation,
as well as the coupling between micro-ring resonators and
waveguides.
7597-32, Session 7
Three-dimensional meshfree numerical method for optical
structuresF. Alharbi, King Abdulaziz City for Science and
Technology (Saudi Arabia) and IBM Almaden Research Ctr. (United
States); J. C. Scott, IBM Almaden Research Ctr. (United States)
A new and efficient three dimensional multi-domain spectral
method formulation is developed to simulate and analyze optical
structures. The formulation is meshfree and functional expansion
based where the unknown physical quantities are approximated by
expansions by preselected basis sets. The expansion coefficients
are satisfying the governing equations. This is the fundamental
difference between spectral methods and the conventional finite
difference and finite element methods, where the unknown quantities
are approximated by their values at meshing points.
To enhance the performance of the method, the computational
window is divided into domains where the structural functions are
smooth. This allows avoiding the errors that are caused by the
Gibbs phenomenon, which is associated with discontinuities. For
bounded domains, Chebyshev polynomials and Fourier series are used
and predefined exponential basis sets are used for half-bounded
ones.
The formulation is very flexible where multiple coupled physical
quantities can be obtained simultaneously. For example, in the case
of electromagnetic field, the three electric field components are
solved concurrently. Also, the boundary conditions are considered
analytically without any approximation. Additionally and as common
for spectral methods, the method is very accurate and fast. This is
mainly because the approximation by expansion reduces the numerical
time and memory requirements.
The method is used to study wave propagation and scattering and
modal behavior of many optical structures. To demonstrate the
validity and the accuracy of the presented method, it is compared
with various published methods, where many optical structures are
studied.
7597-33, Session 7
Synthesis of titanium indiffused LiNbO3 waveguides with desired
modal fieldsE. K. Sharma, Univ. of Delhi (India); G. J. Saxena,
Univ of Delhi (India)
In this paper we report a procedure based on variational
approximation, to obtain the refractive index profile and in turn
the process parameters
for fabrication of waveguide from the desired modal field. It
has been shown that the best variational separable field for a
channel waveguide corresponds to the solution of two equivalent
planar waveguides in the x and y directions. We show that for a
desired modal field X(x)Y(y), one can obtain the refractive index
profile parameters , h and w. We have illustrated the use of the
procedure in the design of waveguides for optimum coupling
efficiency between a fiber and waveguide. Assuming the separable
channel waveguide field it is possible to extract the optimal modal
field parameters and hence, the refractive index profile
parameters, for maximum coupling efficiency which in turn define
the process parameters or fabrication conditions of the waveguide
such as temperature and time of diffusion, width and thickness of
the titanium strip. For a given strip width, each profile width w
corresponds to a fixed profile depth h. In an attempt to maximize
coupling efficiency along the x-direction to unity by appropriate
choice of X(x) for a typical communication fiber, we realized that
the corresponding w resulted in an h which reduced efficiency in
the y-direction to a very small value. Hence, it was necessary to
compromise on the choice of X(x); we restricted the choice so as to
obtain an efficiency of above 90% in the x-direction. With this
choice it is possible to find an appropriate h and n for maximum
coupling efficiency. Once the three parameters h, w and are known,
the strip thickness, time and temperature can be defined. The
results have been validated by comparison with those obtained by
simulation on the BPM CAD simulator.
7597-34, Session 8
InAs quantum dot-based devices for ultrafast photonic signal
processingO. Wada, Kobe Univ. (Japan)
This paper discusses first the quantum dot (QD) growth technique
based on molecular beam epitaxy (MBE), and then describes their
application to photonic devices for ultrafast telecommunications
such as SOAs and all-optical switches. An important issue in
QD-SOAs is the polarization sensitivity which is primarily caused
by the flattened shape of QDs. We have introduced our unique
approach of columnar dot technique in which a number of QD layers
are closely stacked to form a better geometrical isotropy. By
optimizing the geometry and strain in InAs/InGaAs/InP QD system,
polarization-insensitive SOA performance has been demonstrated for
the first time at 1.55 mm. We also propose an alternative approach
of using remotely stacked QD layers and demonstrate basic
polarization-insensitive characteristics. As for all-optical
switches, recent result of vertical structure QD-based all-optical
switches is described. This switching device has a vertical cavity
composed of a pair of asymmetric distributed Bragg reflectors
(DBRs) incorporating a QD nonlinear medium. Through optimizing the
design and fabrication of vertical structure all-optical devices,
optical reflection-type switch response with a time constant as
fast as 23 ps has been demonstrated. We thus illustrate the unique
prospects of QD-based devices to future photonic communication and
signal processing systems.
7597-35, Session 8
Thermal crosstalk reduction in IR thermo-electric photodetectors
by lock-in method: 4D numerical simulations and experimental
verificationW. Vandermeiren, J. Stiens, C. De Tandt, Vrije Univ.
Brussel (Belgium); G. Shkerdin, V. Kotov, Institute of Radio
Engineering and Electronics (Russian Federation); G. Borghs, IMEC
(Belgium); P. Muys, Lambda Research Optics Europe (Belgium); R.
Vounckx, Vrije Univ. Brussel (Belgium)
Laser induced temperature distributions inside doped
semiconductor materials are used to derive laser beam profiles by
means of the thermo-
Conference 7597: Physics and Simulation of Optoelectronic
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electric Seebeck effect. Thermal diffusion will lead to a
discrepancy between the optical intensity profile of the laser beam
and the measured temperature distribution inside the semiconductor.
An advanced numerical 4D finite element model describing the laser
induced spatial temperature distribution in function of time in a
layered GaAs based structure was developed in Comsol Multiphysics.
Non-linearities as the temperature dependence of the absorption
coefficient, the thermal conductivity and the Seebeck coefficient
were taken into account. This model was used to investigate the
optical chopper frequency dependence on the spatial thermal
crosstalk level and the responsivity near the illuminated surface
of the detector structure. It was shown that the frequency
dependent crosstalk level can be reduced significantly by applying
short chopping periods with respect to the thermal diffusion time
constant. The thermal crosstalk is reduced to -10dB and -20dB for
the first and second neighboring pixel respectively for a lockin
frequency of 300 Hz. Experimental results of the spatial thermal
crosstalk level and the responsivity were compared with simulations
and satisfactory agreements between both were achieved. High power
CO2 laser profile measurements obtained with our thermoelectric
detector and a commercially available Primes detector were
compared.
7597-37, Session 8
Ultrafast compact silicon-based ring resonator modulators using
metal-insulator switching of vanadium dioxideJ. Nag, J. D. Ryckman,
R. F. Haglund, Jr., S. M. Weiss, Vanderbilt Univ. (United
States)
We describe an optical modulator based on a silicon ring
resonator coated with vanadium-dioxide (VO2) motivated by the need
for compact silicon-compatible optical switches operating at THz
speeds. VO2 is a functional oxide undergoing metal-insulator
transition (MIT) near 67C, accompanied by huge changes in
electrical resistivity and near-infrared transmission. The MIT can
be induced thermally, optically (by ultra-fast laser excitation in
less than 100fs), and possibly with electric field. The ability to
optically induce an ultrafast phase change in VO2 presents an
excellent opportunity to realize high speed all-optical modulation
in compact device structures. During transition, the large change
in the refractive index (~1.96-3.25) in the near infrared, renders
VO2 appropriate for integration with silicon-based ring resonators
at telecommunication frequencies. VO2 is easily deposited on
silicon and its ultrafast switching properties can be used to tune
the effective index of ring resonators instead of depending on the
weak electro-optic properties of silicon. The VO2-silicon ring
resonator is thus expected to operate at speeds up to 10 THz
utilizing low Q-factor, with shorter cavity lifetimes, thus
enabling faster, more robust device response while maintaining
compact device size. We are carrying out a proof-of-concept study
using double-layer e-beam lithography to make ring resonator
structures on SOI substrates with rings varying in diameter from 2-
22 um coupled to 98um-long nanotapered waveguide at a separation of
200nm. The rings will be coated with 50nm of VO2 by pulsed laser
deposition. Our FDTD simulation results predict large modulation
effects by switching the VO2 thermally.
7597-76, Session 8
Finite difference time domain analysis of ultra-broadband
enhanced absorption of silicon surface with nanostructuresH. Wang,
C. Chen, J. Wu, National Chung Cheng Univ. (Taiwan); S. Feng,
National Univ. of Kaohsiung (Taiwan); S. Liu, National Chung Cheng
Univ. (Taiwan)
We investigate the ultra-broadband enhanced absorption
properties in a wavelength range of 0.3~1.2 μm for silicon surface
with nanostructures by using finite difference time domain (FDTD)
algorithm. Three different types of surface structures including
cone-like, air-hole, and inverted Pyramids structures are
simulated. We demonstrate absorptance enhancement of silicon
surface with varying different geometric arrangements, structure
sizes, and shapes. The best enhancement structure is cone-like type
which can suppress the reflection of surface about 2.5%. We design
a special arrangement for air-hole type surface that can increase
the absorption of solar surface about 65%. In the inverted Pyramids
structures, we find the U shape of structure will increase the
absorption efficiency due to a gradual change of refractive index.
The physics of such remarkable absorption for the structured
silicon surfaces are discussed as well.
7597-40, Session 9
Random lasing in nanocrystalline ZnO powdersH. Kalt, J. Fallert,
R. Dietz, J. Sartor, D. Schneider, C. F. Klingshirn, Univ.
Karlsruhe (Germany)
We study the properties of random lasing modes in
nanocrystalline ZnO powders by spatially resolved high-excitation
photoluminescence spectroscopy. Both localized and extended modes
are observed in the same spatial region of the powder. We find that
the localized modes appear at much lower optical gain than the
extended ones as predicted by theory.
7597-41, Session 9
Control random laser modes by local pumpingH. Cao, Yale Univ.
(United States)
A difficulty concerning the practical application of random
lasers is the lack of precise control over lasing mode properties.
We show that the lasing modes can be modified by inhomogeneous
pumping of random media. The spatial inhomogeneity of gain causes
dramatic and complicated changes of the lasing modes even in the
absence of gain saturation. Some lasing modes disappear, while new
modes are created at various frequencies.
Conference 7597: Physics and Simulation of Optoelectronic
Devices XVIII
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SPIE Photonics West 2010 · spie.org/pw594 Return to Contents
7597-42, Session 9
Visible-wavelength random lasing of (Zn,Cd,Mg)O quantum well
structuresS. Kalusniak, S. Sadofev, J. Puls, H. Wuensche, F.
Henneberger, Humboldt-Univ. zu Berlin (Germany)
Semiconductor lasers operating in the visible wavelength range
have been a subject of extensive research during the past years.
Ternary ZnCdO is a material with considerable potential in this
regard, as it can cover in principle band-gaps from the ultraviolet
to the near infrared spectral range.
We have systematically fabricated (Zn,Cd)O/ZnO single and
multiple quantum well structures and elucidated their optical
properties. In the low-density excitation regime, huge
polarization-induced electric fields of some 108 V/m are signified
by a strong red shift of the photoluminescence band with increasing
well width as well as an increase of the lifetime from the ps- to
the μs-time scale. Effective screening of these fields occurs
already at moderate optical excitation in the 10 kW/cm² range and
recovers practically the bare quantum-confined transition energies
and short lifetimes. In the same excitation range laser action of
specially designed multiple quantum well structures is observed.
The low-temperature lasing threshold is only 25 kW/cm² and
increases moderately up to room temperature (150 kW/cm²). The
emission wavelength is systematically tuneable by structure design.
The longest lasing wavelength achieved so far is 510 nm at room
temperature.
The laser action can be achieved without preparation of an
optical cavity. Both spectral position and separation of the lasing
modes are determined by the geometrical shape of excitation area
and vary with the excitation power. A theoretical model assuming
weak scattering reproduces the experimental finding reasonably
well. For specially prepared micro-resonators, narrowing of the
mode band and mode selection is demonstrated.
7597-43, Session 10
Lasing osicllation in a single quantum dot nanocavity system
under strong/weak coupling regimeY. Arakawa, M. Nomura, S. Iwamoto,
Y. Ota, N. Kumagai, The Univ. of Tokyo (Japan)
We dicuss recent advances in light-matter interaction in a
single quantum dot embedded with photonic crystal nanocavity. We
have successfully demonstrated a transition from strong coupling
regime to lasing oscillation by the single dot gain.
7597-44, Session 10
Radiative efficiency of MOCVD grown quantum dot lasersL. J.
Mawst, G. Tsvid, P. Dudley, J. Kirch, J. H. Park, Univ. of
Wisconsin-Madison (United States)
Quantum dot lasers have been reported by MBE growth with high
performance, although previous reports indicate that the overall
radiative efficiency (i.e. Jspon/Jtotal) from such structures is
surprisingly low (5-25%). Here, we study the gain and radiative
efficiency of MOCVD grown InGaAs quantum dot lasers. Single-pass,
multi-segmented amplified spontaneous emission measurements are
used to obtain the gain, absorption, and spontaneous emission
spectra in real units. Integration of the calibrated spontaneous
emission spectra then allows for determining the overall radiative
efficiency, which gives important insights into the role which
nonradiative recombination plays in the active region under study.
We use single pass, multi-segmented edge-emitting in which
electrically
isolated segments allow to vary the length of a pumped region.
In this study we used 8 section devices (the size of a segment is
50x300 μm) with only the first 5 segments used for varying the pump
length. The remaining unpumped segments and scribed back facet
minimize round trip feedback. Measured gain spectra for different
pump currents allow for extraction of the peak gain vs. current
density, which is fitted to a logarithmic dependence and directly
compared to conventional cavity length analysis, (CLA). The
extracted spontaneous emission spectrum is calibrated and
integrated over all frequencies and modes to obtain total
spontaneous radiation current density and radiative efficiency. We
find radiative efficiency values of approximately 25% at RT for 5
stack QD active regions. By contrast, high performance InGaAs QW
lasers exhibit radiative efficiency ~50% at RT.
7597-45, Session 10
Inhomogeneous quantum dot gain medium for improved spatial
coherence in wide-aperture semiconductor lasersJ. Mukherjee,
Tyndall National Institute (Ireland); J. G. McInerney, Univ.
College Cork (Ireland)
Scaling the brightness (spatial coherence) along with output
power has been a long-standing problem for semiconductor lasers.
The difficulty arises due to complex spatio-temporal modal
filamentation associated with light-matter interaction in the
non-linear semiconductor lasing medium. We have done a detailed
theoretical study of spatio-temporal dynamics in wide aperture
semiconductor lasers in order to identify factors limiting spatial
coherence in the high power regime, thereby finding routes to scale
the brightness using the unique properties of quantum confined
active regions. In this context, we have developed a detailed
opto-electro-thermal model, based on Maxwell-Bloch formalism, to
describe frequency-, carrier- and temperature-dependent gain and
dispersion. First a steady-state electro-thermal model is developed
to simulate the current and heat spreading in the laser. The
thermal model is then used in conjunction with the Maxwell-Bloch
based dynamical model to obtain pump-dependent modal intensity
structure and spatial frequency spectral characteristics. Effects
of both homogeneous and inhomogeneous gain broadening are analysed.
It is shown, via linear stability analysis and high resolution
space-time adaptive FEM simulations that crystal growth induced
inhomogeneous gain broadening in quantum dot lasers enhances
spatial coherence and leads to suppressed filamentation and stable
far-fields in both thermal and non-thermal regimes even when the
phase-amplitude coupling is comparable to that in quantum well gain
medium. Strong spatial-mode competition in the inhomogeneously
broadened gain medium under cw operation is also highlighted.
7597-46, Session 10
Bipolar self-consistent optoelectronic model for quantum dot
lasersA. Martín-Mínguez, H. Odriozola, I. Esquivias, J. M. G.
Tijero, Univ. Politécnica de Madrid (Spain); E. Pavelescu, J. P.
Reithmaier, Univ. Kassel (Germany)
We present a simulator for Quantum Dot (QD) laser diodes. The
simulator solves the complete bipolar semiconductor equations for
the heterostructure. The special features of QD active layers are
included through a multi-population non-equilibrium QD model. The
interactions between the bulk material and Wetting Layer (WL), and
between WL and each QD level and size are considered in terms of
carrier capture/escape processes. The model includes inhomogeneous
broadening due to the different QD size, homogeneous broadening in
the gain, Shockley-Read-Hall, spontaneous and Auger recombination
terms for bulk, WL and QD carriers.
The simulator is applied to 920 nm and 1060 nm lasers based on
InGaAs/(Al)GaAs.
Conference 7597: Physics and Simulation of Optoelectronic
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The influence of theoretical parameters, such as the homogeneous
and inhomogeneous broadening, recombination parameters, capture
times, band-offset, on the laser performance is analyzed. It is
found that the maximum achievable gain depends on the symmetry of
the QD electron and hole densities, which in turn depends on the
band alignment. The simulation results are compared with
experiments in broad area QD lasers. A high contribution of the
bulk and/or WL non-radiative recombination terms has to be assumed
to obtain a good agreement between the experimental and simulated
threshold current densities and slope efficiencies. The measured
temperature dependence of the emission wavelength for devices with
different cavity lengths is reproduced in the simulations.
7597-47, Session 10
Bandwidth improvement by manipulating the high-frequency
roll-off of an injection-locked QD laser operating at 1310 nmN. A.
Naderi, M. C. Pochet, The Univ. of New Mexico (United States); V.
Kovanis, Air Force Research Lab. (United States); L. F. Lester, The
Univ. of New Mexico (United States)
The high-speed modulation characteristics of an injection-locked
quantum dot Fabry-Perot semiconductor laser operating at 1310-nm
under strong injection are investigated experimentally with a focus
on the enhancement of the modulation bandwidth. The coupled system
consists of a small-signal modulated quantum dot slave
injected-locked by a CW DFB laser as the master. At particular
injection strengths and frequency detuning levels between the
master and slave laser, a unique modulation response is observed
that differs from the typical modulation response observed in
injection-locked systems. This unique response is characterized by
a rapid low-frequency rise along with a 20 dB per decade
high-frequency roll-off (typically 40 dB per decade) that enhances
the 3-dB bandwidth of the locked system at the expense of losing
modulation efficiency of about 20 dB at frequencies below 1 GHz.
Such behavior has been previously observed both experimentally and
theoretically in the high-frequency response characteristic of an
injection-locked system using an externally-modulated master;
however, the results shown here differ in that the slave laser is
directly-modulated. The benefit of the observed response is that it
takes advantage of the enhancement of the resonance frequency
achieved through injection-locking without experiencing the low
frequency dip that significantly limits the useful bandwidth in the
conventional injection-locked response. The second benefit of this
unique response is the improvement in the high frequency roll-off
that extends the bandwidth. Finally a bandwidth improvement of ~7
times compared to the free-running slave laser has been
achieved.
7597-48, Session 11
Modeling of photonic-crystal-based high-power high-brightness
semiconductor lasersV. Shchukin, PBC Lasers GmbH (Germany); V.
Kalosha, N. Ledentsov, D. Bimberg, Technical University of Berlin
(Germany)
Modeling of semiconductor lasers based on multilayer epitaxial
structures with ultrabroad vertical and ultrabroad lateral
waveguides (WGs) suggests unique possibilities to fabricate high
power high brightness lasers. Ultrabroad WGs are extremely
advantageous as they allow extracting high power from a single
chip, keeping low beam divergence and reducing undesirable
non-linear effects in the gain medium, while one must ensure single
mode lasing from a broad WG. Novel concepts addressing this
challenge have been developed including vertical photonic crystal
formed by epitaxial multilayer structure, lateral photonic crystal
fabricated by multistripe processing with selective pumping of
stripes, tilted wave laser based on phase matching effects in the
propagation of optical modes in coupled resonators. The results
have been employed in the fabrication of practical semiconductor
lasers.
Experimental results on high brightness lasers are presented [1]
for the wavelength regions of 635-660 nm, 850 nm, 980 nm, and 1060
nm.
[1] Dieter Bimberg et al, Photonics West 2010, OE120
7597-49, Session 11
Applying the joint Wigner time-frequency distribution to
characterization of ultra-short optical pulses in the actively
mode-locked semiconductor laser with an external single-mode fiber
cavityA. S. Shcherbakov, P. Moreno Zarate, National Institute for
Astrophysics, Optics and Electronics (Mexico); J. Campos Acosta,
Consejo Superior de Investigaciones Científicas (Spain); Y. V. I.
Il’n, I. S. Tarasov, A.F. Ioffe Physical-Technical Institute
(Russian Federation)
An attempt is made to develop an approach to characterization of
high-repetition-frequency trains including low-power picosecond
optical pulses with an internal frequency modulation in both time
and frequency domains in the case of exploiting semiconductor
lasers matched effectively by an external single-mode fiber cavity.
For these lasers, we analyze non-conventional regimes of the active
mode-locking, which are connected with injecting various modulating
signals and appearing specific composite states of a multi-pulse
active mode-locking. Then, our approach uses the joint Wigner
time-frequency distributions, which can be found due to involving
the recently developed interferometric technique. In so doing, the
modified scanning Michelson interferometer was exploited for
shaping the field-strength auto-correlation functions peculiar to
the above-mentioned types of light radiation. Theoretically, the
Wigner distribution has an infinite resolution in time due to
absence of averaging over any finite time interval. Moreover, for
any finite lag length, it has an infinite frequency resolution.
Together with this, the Wigner distribution being quadratic in
nature is able to introduce various cross terms for a
multi-component signal. For our analysis and creating the Wigner
distributions, the data of experiments carried out with the
InGaAsP/InP-heterolasers, operating at a wavelength of 1300 nm, had
been used. When the optical signal consisted of contiguous
ultra-short pulses with the repetition frequency up to 1.5 GHz, due
to operating the semiconductor lasers in various active
mode-locking regimes, typical pulse train-average auto-correlation
functions had been characterized by temporal widths of about 3-15
ps. Additionally, stability of the chosen active mode-locking
regimes had been followed and estimated.
7597-50, Session 11
Stability analysis of (Al,In)GaN laser diodes in an external
cavityU. T. Schwarz, Fraunhofer-Institut für Angewandte
Festkörperphysik (Germany); H. Braun, Regensburg Univ. (Germany);
C. Raab, A. Able, F. Lison, Toptica Photonics AG (Germany)
We investigate experimentally and theoretically the spectral and
dynamic properties of grating stabilized external cavity diode
lasers (ECDL) with blue to UV (Al,In)GaN laser diodes. Operation in
a single longitudinal mode of the external resonator results in
extremely narrow linewidth and large coherence length. The
frequency-selective feedback allows tuning of the laser wavelength
and locking to an external reference. Here, a Littrow design is
used for the grating stabilized ECDL employing commercial
(Al,In)GaN laser diodes. The behaviour of the blue and UV laser
diodes in combination with the grating is markedly different from
red and IR laser diodes in an identical setup.
We use the rate equation model as described by Lang and
Kobayashi to simulate the dynamics of the laser diode in a cavity
with external feedback. This model provides linewidth and sidemode
suppression.
Conference 7597: Physics and Simulation of Optoelectronic
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Coherence collapse and the chaotic regime of laser dynamics are
also well described. We take the input parameters from other
measurements of (Al,In)GaN laser diodes, in particular optical
gain, antiguiding factor, mirror reflectivity, carrier density, and
carrier lifetime from Hakki-Paoli and streak camera measurements
which were carried out in our laboratory. For comparison with red
and IR laser diodes, we rely on parameter sets from literature.
The model reproduces the measured behaviour of the (Al,In)GaN
ECDL extremely well. The dependency of the width of stability
plateaus on injection current is in agreement with the experimental
observation. Our preliminary result is that the Lang-Kobayashi
model describes grating-stabilized ECDL in the blue and UV region
as well as for red and IR ECDL. The experimentally observed
difference between blue/UV and red/IR ECDL in terms of stability is
reproduced by the simulation.
7597-51, Session 11
Semiconductor laser oscillation-frequency stabilization using
the Faraday effectH. Arai, A. Sato, A. Sato, K. Nakano, T. Sato, M.
Ohkawa, Niigata Univ. (Japan)
The semiconductor lasers in use today are on one hand, prized,
and highly praised, for their small size, light weight, longevity
and energy-efficiency, -and on the other, criticized for their
susceptibility to frequency-fluctuations brought about by changes
in temperature and drive current. Once this “wrinkle” is ironed
out, semiconductor lasers will become the default light-sources,
for satellites’ onboard interferometers.
Our studies have been directed at stabilizing oscillation to the
atomic absorption line frequency reference, and using negative
electrical feedback to the injection current. Frequency
stabilization is accomplished, by either; a) applying direct
modulation to the semiconductor laser’s drive current, or b)
modulating the reference frequency, to obtain the error signal
needed for stabilization. In this instance, Faraday effect-based
stabilization was used. This indirect oscillation frequency
stabilization has no discernable effect on spectra width, but,
stability was no better than that observed in the system using the
direct modulation.
When we compared Faraday effect- and direct modulation methods
of stabilization, in order to uncover the root-cause of the
discrepancy, sensors picked up system noise, the source of which
was heat generated by the heavy current applied to a magnetic coil
used to apply the Faraday effect. We also substituted a permanent
magnet for the electromagnet.
7597-52, Session 11
Accurate source simulation in modern optical modeling and
analysis softwareD. A. Jacobsen, E. R. Freniere, M. Gauvin, Lambda
Research Corp. (United States)
Modern optical modeling and analysis programs allow users to
create and analyze accurate optical and opto-mechanical systems in
the software environment prior to building actual hardware based
systems. The resultant accuracy of these models depends on the
accuracy of the components that make up the model including the
light source characteristics, surface and material properties, and
the model geometry. In this paper we will consider factors that
lead to improved modeling of the light source such as spectral and
angular properties, the spatial distribution of light within the
source, and the interaction of the light with the structure of the
source. These factors are extremely important for near field
modeling, especially for fiber and light pipe coupling. Several
options will be discussed including simple source models such as
point sources, ray files, surface properties that define optical
parameters such as spectral and angular distribution, and detailed
3D solid models of the source. Simulated results for spectrum,
angular, and spatial distribution will be compared to actual
measurements for a variety of source types. Discussion will also
include the appropriateness of each modeling approach with respect
to different applications.
7597-67, Poster Session
Blue-emitting ZnSe random laserT. Takahashi, T. Nakamura, S.
Adachi, Gunma University (Japan)
In contrast to the conventional semiconductor diode lasers,
semiconductor random lasers can emit light without having
Fabry-Perot resonators. Random laser action is known to be caused
by strong multiple scattering of the emitted lights and light
amplification in the disordered gain medium. Random laser shows
unique characteristics, such as low threshold, spatial emission,
and high coherency. It is clear that it is very important to
develop random lasers emitting in the visible spectral region.
However, most of the semiconductor random lasers (e.g., ZnO and GaN
lasers) emit light in the near-UV region. ZnSe has an excitonic
band gap of ~2.7 eV at room temperature and is, therefore, a
promising material for realizing random laser in the visible
spectral region. In this work, we report lasing action and
characteristics of a blue-emitting ZnSe random laser at room
temperature. Below the threshold excitation, we observe only a
broad spontaneous emission peaking at ~470 nm. Above the threshold,
several discrete lasing lines are observed to grow at the center of
the spontaneous emission (~475 nm). The lasing line width is less
than 0.4 nm which is found to be about 40 times smaller than the
spontaneous emission.
7597-68, Poster Session
All optical logic gates using active plasmonic device blockG.
Oh, Chung-Ang Univ. (Korea, Republic of); D. Kim, Korea Photonics
Technology Institute (Korea, Republic of); H. Kim, Y. Choi,
Chung-Ang Univ. (Korea, Republic of)
Optical logic gates are essential requirement for achieving
optical signal processing and optical computing systems. Though
intensity-dependent all optical logic gates such as Mach-Zehnder
interferometers and distributed-Bragg gratings have been
researched, these methods based on nonlinear planer waveguide
devices have disadvantages in size, switching time, and energy
loss. In this work, we propose a novel all optical logic gates
based on active plasmonics that may control the electron-photon
coupling through an external effect. The phenomenon of surface
plasmon resonance is basically appeared on attenuated total
reflection mirror block. Under this resonance condition, the
incident light gets highly absorbed and loses a fair amount of its
energy, resulting surface plasmon polaritons wave (SPW) at the
metal surface. The SPW is the propagation of the bound oscillation
resulted by the electron-photon coupling, and can be controlled by
external light. In this paper, we study a simple block for
all-optical logic gate by using active plasmonics with specific
metal layer configuration such as photonic crystal. In our
structure, it is possible to control the propagating light in the
prism by an external light under resonance condition. We also
optimize this configuration by finite-difference time-domain method
for metal layer configuration. Finally, we consider an optical
NAND-gate using active plasmonics based on double device block.
More detailed results and discussions will be presented.
7597-69, Poster Session
Formulation of differential transfer matrix method in
cylindrical geometryM. Jiani, M. Vesal, S. Khorasani, B. Rashidian,
Sharif Univ. of Technology (Iran, Islamic Republic of)
Transfer and scattering matrix methods are widely in use for
description of the propagation of waves in multilayered media. When
the profile of refractive index is continuous, however, a modified
formulation of transfer matrices does exist, which provides a
complete analytical solution of the wave phenomena in such
structures. For this purpose, we have previously formulated and
reported the Differential Transfer Matrix
Conference 7597: Physics and Simulation of Optoelectronic
Devices XVIII
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TEL: +1 360 676 3290 · +1 888 504 8171 ·
[email protected] 597Return to Contents
Method (DTMM) [1-4].
Previously reported variations of the so-called DTMM had been
limited to Cartesian geometry where layered media form
one-dimensional structures and plane waves are used as basis
functions. In this work, we extend the formalism to cylindrical
geometry with radial symmetry, in which Bessel functions need to be
employed as basis functions. Hence, complete analytical formulation
of the DTMM under radial and axial symmetry is described and
derived.
[1] S. Khorasani, and K. Mehrany, “Analytical Solution of Wave
Equation for Arbitrary Non-homogeneous Media,” Proceedings of SPIE,
vol. 4772, pp. 25-36, Seattle (2002).
[2] S. Khorasani, and K. Mehrany, “Differential Transfer Matrix
Method for Solution of One-dimensional Linear Non-homogeneous
Optical Structures,” Journal of Optical Society of America B, vol.
20, no. 1, pp. 91-96 (2003).
[3] K. Mehrany, and S. K