[1]
"Gain spectra of (GaIn)(NAs)
laser diodes for the 1.3µm wavelength regime"
by: M.Hofmann, A.Wagner, C. Ellmers, C.Schlichenmeier, S.Schäfer,
F.Höhnersdorf, J.Koch, C.Agert, S.Leu, W.Stolz, S.W.Koch,
W.W.Rühle, J.Hader, J.V.Moloney, and E.P.O'Reilly, Appl.
Phys. Lett. 78 (20), 3009 (2001).
Gain spectra of (GaIn)(NAs)/GaAs quantum-well lasers operating
in the 1.3µm emission wavelength regime are investigated
experimentally and theoretically. The results are compared to
those for a commercial (GaIn)(AsP)/InP structure. The former type
of structure shows significantly higher gain band width at higher
carrier densities.
(The comparison between the experimental and theoretical
gain is shown in the examples section.)
[2]
"Clamping of the linewidth
enhancement factor in narrow quantum-well semiconductor lasers"
by: J.Hader, D. Bossert, J.Stohs, W.W.Chow, S.W.Koch, and J.V.Moloney,
Appl. Phys. Lett. 74 (16), 2277 (2000).
The linewidth enhancement factor (LWEF) in GRINSCH quantum-well
lasers is investigated theoretically and experimentally. For thin
wells, a small LWEF is obtained which clamps with increasing carrier
density, in contrast to the monotonous increase observed in thicker
wells.
(The comparison between the measured and calculated
LWEF is shown in the
examples
section.)
[3]
"Measurement
and calculation of gain spectra for (GaIn)As/(AlGa)As single quantum
well lasers" by: C.Ellmers, A.Girndt, M.Hofmann,
A.Knorr, W.W. Rühle, F.Jahnke, S.W.Koch, C.Hanke, L.Korte,
and C.Hoyler, Appl. Phys. Lett. 72 (13), 1647 (1998).
Compares
experimental gain spectra for a (gaIn)As/(AlGa)As single quantum
well laser to ones calculated with a fully microscopic approach.
The found agreement demonstrates the predictive capability of
the theoretical model.
(The
comparison between the measured and calculated gain is shown in
the
examples
section.)
[4]
"Comparison
of experimental and theoretical gain-current relations in GaInP
quantum well lasers" by: P.M. Smowton, P.Blood,
and W.W.Chow, Appl. Phys. Lett. 76 (12), 1522, (2000).
Results
for gain and recombination currents obtained from spontaneous
emission spectra of a fully microscopic laser theory are compared
to experimental results. From the comparison the inhomogeneous
broadening in the experimental samples is determined.
(Parts
of the comparison between the experimental and theoretical gain
is shown in the
examples
section.)
[5]
"Field-dependent absorption
in superlattices: Comparison of theory and experiment"
by: A.Thränhardt, H.J.Kolbe, J.Hader, T.Meier, G.Weiser,
and S.W.Koch, Appl. Phys. Lett., 73 (18), 2612 (1998).
Calculated
absorption spectra of electronically coupled GaInAs/InP multiquantum-well
structures (superlattices) under the the influence of external
applied electric fields are compared to experimental ones.
(Parts of the comparison between the experimental
and theoretical results is shown in the
examples
section.)
[6]
"Calculation
of the excitonic absorption in parabolic semiconductor quantum
well structures" by: A.Thränhardt, J.Hader
and S.W.Koch, Phys. Rev. B 58 (3), 1512 (1998).
Excitonic
absorption spectra for parabolic AlxGa1-xAs quantum wells grown
using the conventional analog technique where the parabolic potential
is produced by varying the Aluminium concentration quadratically
with the growth coordinate are compared to those for structures
grown using the "digital alloy technique". In the later
case the effectively quadratic potential for the electrons and
holes is produced by using electronically coupled wells of same
depth with quadratically varying well width. The influence of
applied electric fields is investigated. The results are compared
to experimental results.
[7]
"Gain
in 1.3µm materials: InGaNAs and InGaPAs semiconductor quantum-well
lasers" by: J.Hader, S.W.Koch, J.V.Moloney,
and E.P.O'Reilly, Appl. Phys. Lett., 77 (5), 630 (2000).
The
absorption and gain for an InGaNAs/GaAs quantum-well laser is
calculated and compared to that of a more conventional InGaNAs/InGaPAs
structure, both lasing in the 1.3µm regime. Despite significant
differences in the bandstructure, the gain value is comparable
for high carrier densities in both structures and the transition
energy at the gain maximum shows a similar blue shift with increasing
carrier density. At low and intermediate densities in the InGaPAs
systyem the differential gain is significantly lower and the bandwidth
smaller than in the InGaNAs system.
[8]
"Influence
of the valence-band offset on gain and absorption in GaNAs/GaAs
quantum-well lasers" by: J.Hader, S.W.Koch,
J.V.Moloney, and E.P.O'Reilly, Appl. Phys. Lett., 76 (25), 3685
(2000).
This
paper gives some detail about the specifics in the theory for
the bandstructure and gain/absorption calculation for Nitrogen
doped GaAs. It is suggested to use the calculated shift of the
transition energy at gain maximum with increasing density to determine
the band-offset in GaNAs/GaAs.
[9]
"Microscopic
modeling of GaInNAs semiconductor lasers"
by: J.Hader, J.V. Moloney, E.P. O'Reilly, M.R. Hofmann, and S.W.Koch,
to be published in Proc. of the SPIE, Photonics West, San Jose
(2001).
The
gain, absorption, differential gain, differential refractive index
and linewidth enhancement factor in GaInNAs/GaAs semiconductor
lasers operating at 1.3 µm is investigated and compared
to those in devices based on InGaAsP/InP and InGaAlAs/InP.
[10]
"Microscopic
theory of gain, absorption and refractive index in semiconductor
laser materials: influence of conduction-band nonparabolicity
and Coulomb-induced intersubband coupling" by:
J.Hader, J.V. Moloney, and S.W.Koch, IEEE J. Quantum Elect. 35
(12), 1878 (1999).
The
influence of the conduction band nonparabolicity and Coulomb coupling
between different electron and differnt hole subbands on gain,
absorption and refractive index in semiconductor heterostructures
is investigated.
[11]
"Modeling semiconductor amplifiers
and lasers: from microscopic physics to device simulation"
by: J.V. Moloney, R.Indik, J.Hader, and S.W.Koch, Journal of the
Optical Society of America B, 16 (11), 2023 (1999).
Results
of full many-body calculations of the optical response of semiconductor
lasers are combined with a full space and time resolved laser
propagation model. The far field broadening for two weakly turbulent
broad-are high-power amplifiers with significantly different linewidth
enhancement factor dependencies on the carrier densities are shown.
[12]
"Semiconductor-Laser
Fundamentals; Physics of the Gain Materials"
by: W.W.Chow, and S.W.Koch, ISBN 3-540-64166-1, Springer-Verlag
Berlin Heidelberg (1999).
Textbook,
explaining the theory of semiconductor lasers. In this book the
basic equations and derivations thereof used in our microscopic
model are shown.
It also shows a theory-experiment comparisons for a CdZnSe structure.
[13]
"Comparison of experimental
and theoretical GaInP quantum well gain spectra"
by: W.W.Chow, P.M.Smowton, P. Blood, A. Girndt, F. Jahnke, and
S.W.Koch, Appl. Phys, Lett. 71 (2), 157 (1997).
Comparison
between experimental and theoretical gain spectra for a GaInP/(AlGa)InP-based
quantum-well laser operating at 680 nm. This article also shows
a comparison between theoretical spectra as calculated with a
fully microscopic approach as ours and ones based on a simplier
model using lineshape functions.
[14]
"Emission
dynamics and optical gain of 1.3µm (GaIn)(NAs)/GaAs lasers"
by: M. Hofmann, N. Gerhardt, A. Wagner, C. Ellmers, F. Höhnsdorf,
J. Koch, W. Stolz, S.W. Koch, W.W. Rühle, J. Hader, J.V.
Moloney, E.P. O'Reilly, B. Borchert, A.Yu. Egorov, H. Riechert,
H.C. Schneider, and W.W. Chow, IEEE Journal of Quantum Electronics,
Vol. 38 (2), 213 (2002).
Studies
experimentally and theoretically the dynamical response of GaInNAs/GaAs
VCSEL's. Shows comparisons between theory and experiment for the
density and temperature dependent gain and threshold.
(The
comparison between the experimental and theoretical gain and threshold
is shown in the
examples
section.)
[15]
"Quantitative Prediction of
Semiconductor Laser Characteristics Based on Low Intensity Photoluminescence
Measurements" by: J. Hader, A.R. Zakharian,
J.V. Moloney, T.R. Nelson, W.J. Siskaninetz, J.E. Ehret, K. Hantke,
M. Hofmann, and S.W. Koch, IEEE Photonics Technology Letters Vol.
14 (6), 762 (2002).
Outlines
and demonstrates the idea of using the predictive character of
the fully microscopic calculations to derive important material
characteristics of semiconductor lasers from experimental low
intensity photoluminescence spectra.
(The
comparison between the experimental and theoretical gain and luminescence
is shown in the
examples
section.)
[16]
"Semiconductor Quantum-Well
Designer Active Materials" by: J. Hader,
A.R. Zakharian, J.V. Moloney, T.R. Nelson, W.J. Siskaninetz, J.E.
Ehret, K. Hantke, S.W. Koch, and M. Hofmann, Optics and Photonics
News, 13 (12), 22 (2002).
A
brief discussion of the main aspects of the idea of using the
predictive character of the fully microscopic calculations to
derive important material characteristics of semiconductor lasers
from experimental low intensity photoluminescence spectra.
[17]
"Microscopic Theory of Gain and Spontaneous
Emission in GaInNAs Laser Material" by:
J. Hader, S.W. Koch, and J.V. Moloney, Solid
State Electron. 47, 513-521 (2003).
Microscopic
models are used to calculate the gain/absorption and the carrier
dynamics in GaInNAs-based quantum-well structures. The gain is
shown to be in very good agreement with the experiment. It is
shown that the carrier capture times depend crucially on details
of the confinement potential. Bandstructure parameterssfor GaInNAs
materials are listed and details of the theory outlined.
[18]
"Microscopic
Modelling of Gain and Luminescence in Semiconductors" by:
J. Hader, J.V. Moloney, S.W. Koch, and W.W. Chow, invited
paper, Journ. Sel. Top. Quant. Electron. 9, 688 (2003).
A collection of comparisons between microscopically calculated
and measured optical material properties for various semiconductor
heterostructures and material systems.
[19]
"Experimental and Theoretical Analysis of Optically
Pumped Semiconductor Disc Lasers" by:
A.R. Zakharian, J. Hader, J.V. Moloney, S.W. Koch, P. Brick, and
S. Lutgen, Appl. Phys. Lett. 83, 1313
(2003).
Based on microscopically calculated optical properties, the the
experimental cw power scaling of optically pumped semiconductor
disk lasers is investigated. Results from initial numerical modeling
are in good agreement with the experimental data, and show that
thermal management is a critical parameter for the temperature-driven
power shutoff in such devices.
[20]
"Linewidth Enhancement Factor and Optical Gain
in GaInNAs/GaAs Lasers" by:
N.C. Gerhardt, M.R. Hofmann, J. Hader, J.V. Moloney, S.W. Koch,
and H.Riechert, Appl. Phys. Lett. 84, 1 (2004).
The microscopic model is used to calculate the linewidth enhancement
factor (LWEF) in GaInNAs-based structures. The results show very
good agreement withe the experiment. The LWEF is found to be rather
density-independent for a given operating wavelength.
[21]
"Structural Dependence
of Carrier Capture Times in Semiconductor Quantum-Well Lasers" by:
J. Hader, J.V. Moloney, and S.W. Koch,
App. Phys. Lett. 85, 369 (2004)
The carrier dynamics in semiconductor multi quantum-well structures
are calculated using a microscopic calculations based on generalized
quantum Boltzmann scattering equations that only use basic bandstructure
parameters. Comparisons of the carrier capture times to experimental
data show very good agreement. Schemes for the optimization of
the capture times are discussed.
[22]
"Nonequilibrium Gain in Optically Pumped GaInNAs Laser Structures" by:
A. Thränhardt, S. Becker, C. Schlichenmaier, I. Kuznetsova,
T. Meier, S. W. Koch, J. Hader, J. V. Moloney, and W. W. Chow,
Appl. Phys. Lett., 85,5526 (2004).
A theory is presented which couples a dynamical laser model to
a fully microscopic calculation of scattering effects. Calculations
for two optically pumped GaInNAs laser structures show how this
approach can be used to analyze nonequilibrium and dynamical laser
properties over a wide range of system parameters.
[23]
"Gain and Absorption: Many-Body Effects" by:
S.W. Koch, J. Hader, A. Thränhardt, and J. V. Moloney,
p. 1 - 25 in: Optoelectronic
Devices, Advanced Simulation and Analysis, ed. J. Piprek, Springer
Verlag, Berlin (2005).
A detailed description of the microscopic calculations of optical
and electronical properties of semiconductor heterostructures,
including theory-experiment comparisons.
[24]
"Type I-Type II Transition in InGaAs/GaNAs
Heterostructures" by:
C. Schlichenmaier, H. Grüning, A. Thränhardt, P.J. Klar,
B. Kunert, K. Volz, W. Stolz, W. Heimbrodt, T. Meier, S.W. Koch,
J. Hader, and J.V. Moloney,Appl. Phys. Lett. 86, 081903 (2005).
Optical interband transitions in a series of InGaAs–GaNAs
quantum well samples are investigated. For changing nitrogen content,
a type I-type II transition is identified by a detailed analysis
of photoluminescence and photoreflectance spectra. Experimental
results are compared systematically with spectra calculated by
a microscopic theory.
[25]
"Quantum-Well Laser Diodes: Temperature and Many-Body Effects"
B. Grote, E.K. Heller, R. Scarmozzino, J. Hader, J.V. Moloney,
and S.W. Koch, p. 27 - 61 in: Optoelectronic Devices, Advanced
Simulation and Analysis, ed. J. Piprek, Springer Verlag, Berlin
(2005).
A detailed description of a simulation of the threshold characteristics
of semiconductor lasers, including thermal and electrical effects.
Simulations based on microscopicly calculated gain tables and
carrier recombination rates are shown to yield very good agreement
with the experiment and to drastically reduce the amount of required
fit parameters.
[26]
"Nitrogen Incorporation Effects on Gain Properties
of GaInNAs Lasers: Experiment and Theory"
A. Thränhardt, I. Kuznetsova, C. Schlichenmaier, S.W. Koch,
L. Shterengas, G. Belenky, N. Tansu, J. Hader, J.V. Moloney, and
W.W. Chow, Appl. Phys. Lett.
86, 201117 (2005).
Gain properties of GaInNAs lasers with different nitrogen concentrations
in the quantum wells are investigated experimentally and theoretically.
Whereas nitrogen incorporation induces appreciable modifications
in the spectral extension and the carrier density dependence of
the gain, it is found that the linewidth enhancement factor is
reduced by inclusion of nitrogen, but basically unaffected by
different nitrogen content due to the balancing between gain and
index changes.
[27]
"Over 3W High-Efficiency Vertical-External-Cavity-Surface-
Emitting Lasers and Applications as Efficient Fiber Laser
Pump Sources"
by: L. Fan, M. Fallahi, J. Hader, A.R. Zakharian, M. Kolesik, J.V.
Moloney, T. Qiu, A. Schülzgen, N. Peyghambarian, W. Stolz,
S.W. Koch, and J.T. Murray, Appl. Phys. Lett. 86, 211116 (2005).
A success report on the design and fabrication of high-power,
high-brightness diode-pumped vertical-external-cavity surface-emitting
lasers using a microscopic gain model.
Over 3 W continuous wave fundamental transverse mode (TEM00) output
at 980 nm with a high slope efficiency of 44% is demonstrated
at room temperature.
[28]
"Microscopic evaluation of spontaneous emission-
and Auger-processes in semiconductor lasers"
by: J. Hader, J.V. Moloney, and S.W. Koch,
IEEE J. Quantum Electronics, 41 (10), 1217 (2005).
The microscopic models used by NLCSTR to calculate spontaneous emission (photo luminescence)
and Auger processes are outlined in this publication. Comparisons of the resulting
loss currents to several experiments show very good agreement. Shortcomings of simper approaches are discussed.
(The main results are shown in
the
examples section).
[29]
"Supression of carrier recombination
in semiconductor lasers by phase-space filling"
by: J. Hader, J.V. Moloney, and S.W. Koch,
Appl. Phys. Lett., 87 (20) 201112 (2005).
The inadequacy of the simple ABC-type power laws that are commonly used
to describe the loss currents due to radiative recombination and Auger
processes is demonstrated. Using the fully microscopic models it is shown that
the density dependencies assumed in these laws can easily lead to errors
of a factor two or more near transparency density and completely break down at higher densities.
(The main results are shown in
the
examples section).
[30]
"Closed-Loop design of a semiconductor laser"
by: J. Hader, J.V. Moloney, L. Fan, M. Fallahi, and S.W. Koch,
Optics Letters, Vol.31 (22), pp. 3300-3302 (2006).
The closed loop design idea is demonstrated for the example of an
InGaAsP/InP-based ridge-waveguide laser. The input-output characteristica
are calculated based soley on the nominal structural design,
low intensity surface emitting PL and information about the internal losses.
Very good agreement with the experiment is demonstrated.
(The main results are shown in
the
examples section).
[31]
"Interband Transitions in InGaN Quantum Wells"
by: J. Hader, J.V. Moloney, and S.W. Koch, in: "Nitride Semiconductor Devices: Principles and Simulation,"
ed. by J. Piprek, Wiley-VCH Verlag, Weinheim (2007).
The theoretical models for describing gain/absorption, spontaneous emission and
carrier losses due to radiative and auger recombination processes in wide bandgap Nitride systems
are described. Several examples are studied with a focus on the influence of piezo electric
and spontaneous polarisation fields.
(A theory-experiment comparison for the gain is shown in
the
examples section).
[32]
"Influence of internal fields on gain and spontaneous
emission in InGaN quantum wells"
by: J. Hader, J.V. Moloney, and S.W. Koch, Appl. Phys. Lett. 89 (17), Art. No. 171120 (2006).
"Erratum: "Influence of internal fields on gain and spontaneous
emission in InGaN quantum wells" [Appl. Phys. Lett. 89, 171120 (2006)"
by: J. Hader, J.V. Moloney, and S.W. Koch, Appl. Phys. Lett. 90, Art. No. 259901 (2007).
The influence of internal electric fields on gain/absorption, spontaneous emission and
carrier losses in wide bandgap Nitride systems
is investigated.
[33]
"Microscopic electroabsorption line shape analysis for
Ga(AsSb)/GaAs heterostructures"
by: C. Bückers, G. Blume, A. Thränhardt, C. Schlichenmaier, P.J. Klar, G. Weiser,
S.W. Koch, J. Hader, J.V. Moloney, T.J.C. Hosea, S.J. Sweeney, J.B. Wang, S.R. Johnson, and Y.H. Zhang,
J. Appl. Phys 101 (3), Art. No. 033118 (2007).
It is shown how the microscopic models can be used to analyze experimental electroabsorption
measurements in order to determine crucial bandstructure parameters like
the band-offset in GaAsSb/GaAs heterostructures.
[34]
"Microscopic simulation of semiconductor lasers at
telecommunication wavelengths"
by: A. Thränhardt, C. Bückers, C. Schlichenmaier, I. Kuznetsova,
S.W. Koch, J. Hader, and J.V. Moloney,
Opt. and Quantum Electron. 38 (12-14), 1005 (2006).
Optical properties are modeled microscopically for GaAs-based laser materials emitting at telecommunication
wavelengths, namely the dilute nitride (GaIn)(NAs) and Ga(AsSb). Excellent agreement with the experiment
is demonstrated and it is shown how one can extract controversial bandstructure parameters such as the
band offset using careful comparisons of measurements and computations.
[35]
"Quantum design of semiconductor active materials: lasers and
amplifier applications"
by:J.V. Moloney, J. Hader, and S.W. Koch,
Laser & Photon. Rev. 1 (1), 24 (2007).
An overview of the first principles quantum approach to design and optimize semiconductor devices for
target wavelengths. Using the microscopic inputs as basic building blocks the LI-characteristic for
a low power InGaAsP ridge laser is predicted without adjustable fit parameters. At the example of a
VECSEL it is demonstrated how the microscopic inputs can be used to develop sophisticated
simulation capabilities for designing and optimizing end packaged high power laser structures.
(Parts of the results are shown in
the
examples sections).
[36]
"Temperature Dependence of Radiative and Auger Losses
in Quantum Wells"
by: J. Hader, J.V. Moloney and S.W. Koch,
IEEE J. Quantum Electron. 44 (2), (2008).
It is demonstated that the classical estimates for the temperature dependence of Auger and radiative
losses in quantum well systems generally fail quite dramatically. While simplified calculations lead to a
1/T-dependence for the radiative losses, microscopic calculations show a 1/T3 dependence
for low densities. At high densities the temperature dependence is much weaker and can no longer
be described by a simple power law. For limited temperature ranges the Auger losses can be described
by an exponential temperature dependence if one uses a density dependent activation energy that can
take positive or negative values. The threshold carrier density is shown to vary more like T2
than the classically assumed linear dependence.
[37]
"On the importance of radiative and Auger losses in GaN quantum wells"
by: J. Hader, J.V. Moloney, B. Pasenow, S.W. Koch, M. Sabathil, N. Linder and S. Lutgen,
Appl. Phys. Lett. 82 (2008).
It is demonstrated that carrier losses due to direct Auger recombination processes
are irrelevant in GaN-based quantum well diodes and lasers. Losses due to radiative recombination
far outweigh Auger losses for all relevant situations. The results demonstrate that the
so-called "efficiency droop" cannot be due to Auger losses.
[38]
"5-W Yellow Laser by Intracavity Frequency Doubling of High-Power Vertical-External-Cavity Surface-Emitting Laser"
by: M. Fallahi, L. Fan, Y. Kaneda, C. Hessenius, J. Hader, H. Li, J.V. Moloney, B. Kunert, W. Stolz, S.W. Koch, J. Murray, and R. Bedford,
IEEE Photon. Technol. Lett. 20, 1700, (2008).
The successfull development of a high power tunable yellow-orange VECSEL
is presented. Using fully microscopic many-body models allowed to
achieve output powers up to 5W at 589nm after a single design-growth iteration.
[39]
"Microscopic theory of the optical properties of Ga(AsBi)/GaAs quantum
wells"
by: S. Imhof, C. Buckers, A. Thraenhardt, J. Hader, J.V. Moloney, and S.W. Koch,
Semicond. Sci. and Technol. 23, 125009 (2008).
Fully microscopic many-body models are used to calculate absorption/gain, PL and carrier losses
due to radiative and Auger processes in dillute bismide materials. A valenceband anticrossing model
for the description of the bandstructure in this new material system is presented and the material
characteristics are studied and compared to those of more conventional materials for the telecom wavelength regime.
[40]
"Microscopic Analysis of Mid-Infrared Type-II "W" Diode Lasers"
by: J. Hader, J.V. Moloney, S.W. Koch, I. Vurgaftman and J.R. Meyer,
Appl. Phys. Lett. 94, 061106 (2009).
Fully microscopic many-body models are used to calculate absorption/gain, PL and carrier losses
due to radiative and Auger processes in antimonide based type-II "W" diode lasers for the mid-infrared wavelength
regime. Excellent agreement with the experiment is demonstrated for PL spectra as wells as the loss currents.
It is shown that the strong degradation of the device performance with increasing temperature is
mostly due to the decrease of the gain with temperature.
(The main results are shown in
the
examples section).
[41]
"Predictive Microscopic Modeling of VECSELs"
by: J. Hader, G. Hardesty, T.-L. Wang, J.M. Yarborough, Y. Kaneda, J.V. Moloney, B. Kunert, W. Stolz and S.W. Koch,
IEEE J. Quantum Electron., 46, 810 (2010).
Based on fully microscopically computed material gain and carrier recombination rates,
the output characteristics of optically pumped VECSELs are calculated. Very good agreement with experimental
results is obtained for surface PL and reflectivity spectra as well as the
operating characteristics using as the only experimental fit
parameter a correction to the pump spot diameter to account for the non-ideal profile of the used pump.
This analysis is also contained in the description of applications of SimuLase that can be downloaded
here.
the
[42]
"Density-activated defect recombination as a possible explanation
for the efficiency droop in GaN-based diodes"
by: J. Hader, J.V. Moloney and S.W. Koch,
Appl. Phys. Lett. 96, 221106 (2010).
A model for density-activated defect recombination is proposed and it is shown
that this model can very succesfully reproduce experimentally measured internal efficiencies
in GaN-based diodes. Combining this model with fully microscopically calculated
radiative carrier losses leads to excellent agreement for the measured efficiency droop.
To download this article click here.
(Copyright (2010) American Institute of Physics. This article may be downloaded for personal use only.
Any other use requires prior permission of the author and the American Institute of Physics.
This article appeared in Appl. Phys. Lett. 96 (2010) and may be found at the following
URL.)
[43]
"Quantum modeling of semiconductor gain materials and
vertical-external-cavity surface-emitting laser systems"
by: C. Buckers, E. Kuhn, C. Schlichenmaier, S. Imhof, A. Thranhardt, J. Hader, J.V. Moloney,
O. Rubelt, W. Zhang, T. Ackermann, and S.W. Koch,
Phys. Stat. Sol. B 247, 789 (2010).
[44]
"Influence of the spatial pump distribution on the performance
of high power vertical-external-cavity surface-emitting lasers"
by: A. Chernikov, J. Herrmann, M. Scheller, M. Koch, B. Kunert, W. Stolz, S. Chatterjee, S.W. Koch,
T.L. Wang, Y. Kaneda, J.M. Yarborough, J. Hader, and J.V. Moloney,
Appl. Phys. Lett. 97, 191110 (2010).
[45]
"340-W Peak Power From a GaSb 2µm Optically Pumped Semiconductor
Laser (OPSL) Grown Mismatched on GaAs"
by: Y.Y. Lai, J.M. Yarborough, Y. Kaneda, J. Hader, J.V. Moloney, T.J. Rotter, G. Balakrishnan,
C. Hains, and S.W. Koch,
IEEE Photon. Technol. Lett. 22, 1253 (2010).
[46]
"Gain of blue and cyan InGaN laser diodes"
by: T. Lermer, A. Gomez-Iglesias, M. sabathil, J. Muller, S. Lutgen, U. Straus, B. Pasenow,
J. Hader, J.V. Moloney, S.W. Koch, W. Scheibenzuber, and U.T. Schwarz,
Appl. Phys. Lett. 98, 021115 (2011).
[47]
"High-Power Optically Pumped Semiconductor Laser at 1040nm"
by: T.-L. Wang, Y. Kaneda, J.M. Yarborough, J. Hader, J.V. Moloney, A. Chernikov, S. Chatterjee, S.W. Koch,
B. Kunert, and W. Stolz,
IEEE Photon. Technol. Lett. 22, 661 (2010).
[48]
"Microscopic simulation of nonequilibrium features in quantum-well
pumped semiconductor disk lasers"
by: E. Kuhn, S.W. Koch, A. Thranhardt, J. Hader, and J.V. Moloney,
Appl. Phys. Lett. 96, 051116 (2010).
[49]
"VECSEL Optimization Using Microscopic Many-Body Physics"
by: J. Hader, T.-L. Wang, J.M. Yarborough, C.A. Dineen, Y. Kaneda, J.V. Moloney, B. Kunert, W. Stolz, and S.W. Koch,
IEEE J. Sel. Topics Quantum Electron. 17, 1753 (2011).
[50]
"Temperature-dependence of the internal efficiency
droop in GaN-based diodes"
by: J. Hader, J.V. Moloney and S.W. Koch,
Appl. Phys. Lett. 99, 181127 (2011).
The experimentally measured temperature dependence of internal efficencies of GaN-based diodes
are analyzed using fully microscopically calculated
radiative carrier losses. Including the radiative losses in an ABC model one finds that one has to
assume Auger losses that are at least two orders of magnitude larger than what theoretical
calculations predict. Also, the droop causing mechanism is found to decrease in strength
with temperature - opposite to the trend usually associated with Auger losses. On the other hand,
the data can be well explained assuming density-activated defect recombination [42] as the droop
causing mechanism.
This article can be found at the following
URL.
[51]
"106 W continuous-wave output power from vertical-external-cavity
surface-emitting laser"
by: B. Heinen, T.L. Wang, M. Sparenberg, A. Weber, B. Kunert, J. Hader, S.W. Koch, J.V. Moloney, M. Koch,
and W. Stolz,
Electron. Lett. 48, 516-U102 (2012).
A report is presented on an optically-pumped semiconductor disk laser providing a continuous-wave output
power of 106 W at a heatsink temperature of 3 degrees C. The laser, which operates in the transversal
multimode regime, emits at a wavelength of 1028 nm. This high output power is achieved by carefully
optimising the chip design, the growth process, and the bonding layer.
[52]
"On the measurement of the thermal impedance in
vertical-external-cavity surface-emitting lasers"
by: J. Hader, T.-L. Wang, J.V. Moloney, B. Heinen, M. Koch, S.W. Koch, B. Kunert, and W. Stolz,
J. Appl. Phys. 113, 153102 (2013).
A detailed and systematic analysis of the loss mechanisms in VECSELs is presented with the goal
to correctly determine the amount of pump power that is converted to heat. With this input,
the accuracy of a recently proposed method for measuring the thermal impedance
based on roll-over characteristics is shown to be very high for devices with and without dielectric coating.
Potential errors arising from non-heating losses can be determined by performing experiments with different
out-coupling mirrors.
The article can be downloaded here.
It appeared in JAP 113, 153102 (2013) and may be found at the following
URL.
Copyright (2013) American Institute of Physics. This article may be downloaded for personal use only.
Any other use requires prior permission of the author and the American Institute of Physics
[53]
"Microscopic analysis of non-equilibrium dynamics in the
semiconductor-laser gain medium"
by: J. Hader, J.V. Moloney, and S.W. Koch,
Appl. Phys. Lett. 104, 151111 (2014).
Fully microscopic models for the calculation of the carrier dynamics and electro-optical response
under non-equilibrium conditions are used to calculate fully self-consitently the response of
an inverted semiconductor quantum well to an intense sub-picosecond pulse. The results show that
spectral hole burning and filling sets basic limits to the achievable pulse amplitude and duration
during applications as mode-locking in VECSELs.
[54]
"15W Single Frequency Optically Pumped Semiconductor Laser With
Sub-Megahertz Linewidth"
by: A. Laurain, C. Mart, J. Hader, J.V. Moloney, B. Kunert, and W. Stolz,
IEEE Poton. Technol. Lett. 26, 131 (2014).
15W CW single frequency output power is demonstrated from a VECSEL that operates at a wavelength of 1020nm
and has a tuning range exceeding 15nm, with a continuous tunability of 9 GHz.
[55]
"Luminescence properties of dilute bismide systems"
by: B. Breddermann, A. Baumner, S.W. Koch, P. Ludewig, W. Stolz, K. Volz, J. Hader, J.V. Moloney,
C.A. Broderick, and E.P. O'Reilly,
J. Lumi. 154, 95 (2014).
Systematic PL measurements on a series of GaBixAs1-x samples are
analyzed theoretically using a fully microscopic approach. Based on sp(3)s* tight-binding calculations,
an effective k.p model is set up and used to compute the band structure and dipole matrix elements for
the experimentally investigated samples. With this input, the PL spectra are calculated
using a systematic microscopic approach based on the semiconductor luminescence equations. The detailed
theory-experiment comparison allows to quantitatively characterize the structures and to
extract important sample parameters.
[56]
"Ultrafast nonequilibrium carrier dynamics in semiconductor laser
mode locking"
by: I. Kilen, J. Hader, J.V. Moloney, and S.W. Koch,
Optica 1, 192 (2014).
Systematic microscopic modeling reveals that ultrafast nonequilibrium kinetic hole burning in
carrier distributions dictates the outcome of femtosecond duration mode-locked pulse formation in VECSELs
The concept of
gain is shown to be no longer meaningful in this limit but the dynamical occupation inversion determines
the final state of the system. The simulation results explain the behavior observed
in key recent experiments and point to the difficulty of achieving pulse durations below 100 fs.
[57]
"Ultrafast pulse amplification in mode-locked vertical external-cavity
surface-emitting lasers"
by: C.N. Bottge, J. Hader, I. Kilen, J.V. Moloney, and S.W. Koch,
Appl. Phys. Lett. 105, 261105 (2014).
A fully microscopic many-body Maxwell-Bloch model is used to investigate the influence of
non-equilibrium carrier dynamics on the short-pulse amplification in mode-locked semiconductor lasers.
The influence of pulse-induced non-equilibrium carrier distributions
in the active region QWs and the saturable absorber is identified. It is shown that for the same
structure, quantum wells, and gain bandwidth the non-equilibrium carrier dynamics lead to two preferred operation
regimes: one with pulses in the (sub-) 100 fs-regime and one with multi-picosecond pulses.
[58]
"Novel type-II material system for laser applications in the near-infrared
regime"
by: C. Berger, C. Moller, P. Hens, C. Fuchs, W. Stolz, S.W. Koch, A.R. Perez, J. Hader, and J.V. Moloney,
AIP Advances 5, 047105 (2015).
The design and experimental realization of a type-II "W"-multiple quantum well heterostructure for emission in the
λ>1.2µm range is presented. The experimental PL for different excitation intensities
is analyzed using microscopic theory. On the basis of the good theory-experiment agreement, the gain properties
of the system are computed using the semiconductor Bloch equations. Gain values comparable to those of type-I systems
are obtained.
[59]
"Optical excitation dependent emission properties of InGaN quantum wells"
by: J. Hader, J.V. Moloney, and S.W. Koch,
J. Computational Electron. 14, 425 (2015).
Fully microscopic many-body calculations are used to study the carrier and polarization dynamics in optically excited
InGaN quantum wells. For (quasi-) CW optical excitation, it is shown that the strong
excitation-induced dephasing leads to an effective spectral width of the created
polarization in the range of several hundred meV. The subsequent polarization to population conversion results in
carrier distributions well above and below the central excitation energy. Without
invoking Auger transitions, it is shown that this can explain experiments by by Binder et al. (Appl. Phys. Lett. 103:071108, 2013)
which observed PL emission from a UV QW after resonant CW excitation of a neighboring green emitting QW.
[60]
"Excitonic transitions in highly efficient (GaIn)As/Ga(AsSb)
type-II quantum-well structures"
by: S. Gies, C. Kruska, C. Berger, P. Hens, C. Fuchs, A.R. Perez, N.W. Rosemann, J. Veletas, S. Chatterjee, W. Stolz,
S.W. Koch, J. Hader, J.V. Moloney, and W. Heimbrodt,
Appl. Phys. Lett. 107, 182104 (2015).
The excitonic transitions of the type-II (GaIn) As/Ga(AsSb) "W"-type QW structure are characterized experimentally
by modulation spectroscopy and analyzed using microscopic modeling. On the basis of the very good agreement between
measured and calculated photoreflectivity, the type-I or type-II character of the observable excitonic transitions
is identified. Despite the type-II character of the fundamental transitions, the structure exhibits a bright luminescence.
[61]
"Fully microscopic modeling of mode locking in microcavity lasers"
by: I. Kilen, S.W. Koch, J. Hader, and J.V. Moloney,
J. Optical Soc. America B-Optic. Phys. 33, 75 (2016).
Microscopic many-body theory is used to analyze mode-locking in a VECSEL with a saturable absorber. The QWs are
treated microscopically through the semiconductor Bloch equations and the light field using Maxwell's equations.
Higher-order correlation effects such as polarization dephasing and carrier relaxation are approximated using
effective rates fitted to second Born-Markov evaluations. For a given gain, the influence of the loss conditions
on the pulse generation in the range above 100fs is analyzed. Optimized operational parameters are identified.
[62]
"Microscopic analysis of saturable absorbers: Semiconductor saturable absorber
mirrors versus graphene"
by: J. Hader, J.H. Yang, M. Scheller, J.V. Moloney, and S.W. Koch,
J. Appl. Phys. 119, 053102 (2016).
Fully microscopic many-body calculations are used to study the influence of strong sub-picosecond pulses on the
carrier distributions and corresponding optical response in saturable absorbers used for mode-locking: semiconductor
(QW) saturable absorber mirrors (SESAMs) and single layer graphene based saturable absorber mirrors (GSAMs).
The dependence of the saturation fluence on the pulses spectral position in both systems is analyzed.
A strong dependence of the saturation fluence on the pulse width in both systems is caused by carrier relaxation
during the pulse. Comparisons of the simulation data to the experiment show a very good quantitative agreement.
[63]
"Type-II vertical-external-cavity surface-emitting laser with Watt level output
powers at 1.2µm"
by: C. Moller, C. Fuchs, C. Berger, A.R. Perez, M. Koch, J. Hader, J.V. Moloney, S.W. Koch, and W. Stolz,
Appl. Phys. Lett. 108, 071102 (2016).
Semiconductor laser characteristics based on type-II QW heterostructures for the emission at 1.2µm are presented.
Ten "W"-QWs consisting of GaAs/(GaIn) As/Ga(AsSb)/(GaIn) As/GaAs are arranged as resonant periodic gain in a
VECSEL. Its structure is analyzed by X-ray diffraction, photoluminescence, and reflectance measurements.
A maximum output power of 4W is demonstrated. A blue shift of the material gain is observed while the modal
gain exhibits a red shift.
[64]
"Design and Fabrication of Hybrid Metal Semiconductor Mirror for High-Power
VECSEL"
by: K. Gbele, A. Laurain, J. Hader, W. Stolz, J.V. Moloney, and S.W. Koch,
IEEE Photon. Technol. Lett. 28, 732 (2016).
The design, fabrication, and characterization of a hybrid metal-semiconductor distributed Bragg reflector (DBR)
for optically pumped VECSEL are reported. The realization of a pure gold reflector attached to an AlGaAs/AlAs DBR
is achieved using a lithography pattern alternating gold and titanium areas for better surface adhesion.
This reduces from 28 to 14, and the number of DBR pairs is needed to achieve a reflectivity above 99.9%.
Experimental results are supported by simulations and show an output power beyond 4 W with an optical efficiency
of 19% and very low thermal impedance.
[65]
"Configuration dependence of band-gap narrowing and localization in dilute
GaAs1-xBix alloys"
by: L.C. Bannow, O. Rubel, S.C. Badescu, P. Rosenow, J. Hader, J.V. Moloney, R. Tonner, and S.W. Koch,
Phys. Rev. B 93, 205202 (2016).
First principle DFT calculations are used to examine the bandgap dependence of dilute GaAsBi on the concentration and
local positioning of Bi-atoms. It is shown that at high concentrations the gap is modified mainly by a Bi-Bi p orbital
interaction and by the large Bi atom-induced strain. The Bi-Bi interactions are shown to depend strongly
on model periodic cluster configurations, which are not captured by tight-binding models. Averaging over various
configurations supports the defect level broadening picture. This points to the role of different atomic configurations
obtained by varying the experimental growth conditions.
[66]
"Charge transfer luminescence in (GaIn)As/GaAs/Ga(NAs) double quantum wells"
by: P. Springer, S. Gies, P. Hens, C. Fuchs, H. Han, J. Hader, J.V. Moloney, W. Stolz, K. Volz, S.W. Koch, and W. Heimbrodt,
J. Lumi. 175, 255 (2016).
Charge transfer excitons are studied in double quantum well structures consisting of a (GaIn)As and a Ga (NAs)
layer separated by a GaAs film of variable thickness. With decreasing barrier thickness, the gradual change from a
spatially direct exciton within the (GaIn)As well to a charge transfer exciton bound across the GaAs spacing layer
is observed. The optical spectra are well reproduced by fully microscopic theory assuming a weak type-I valence
band offset of approximately (45 +/- 40) meV at the Ga(NAs)/GaAs interface.
[67]
"Colliding pulse mode locking of vertical-external-cavity surface-emitting laser"
by: A. Laurain, D. Marah, R. Rockmore, J. McInerney, J. Hader, A.R. Perez, W. Stolz, and J.V. Moloney,
Optica 3, 781 (2016).
A new passive and robust mode-locking scheme for VECSELs is presented. The semiconductor gain medium and the
SESAM are placed strategically in a ring cavity to provide stable colliding pulse operation. The two
counterpropagating pulses synchronize on the SESAM and saturate it together, which minimizes the energy lost.
The interaction of the two counterpropagating pulses is shown
to extend the range of the mode-locking regime and to enable higher output power. Pulse durations of 195 fs are
demonstrated with an average power of 225 mW per output beam at a repetition rate of 2.2 GHz, giving a peak
power of 460 W per beam. The remarkable robustness of the mode-locking is discussed and a rigorous pulse
characterization presented.
[68]
"Electrical injection type-II (GaIn)As/Ga(AsSb)/(GaIn)As single
"W"-quantum well laser at 1.2µm"
by: C. Fuchs, C. Berger, C. Moller, M. Weseloh, S. Reinhard, J. Hader, J.V. Moloney, S.W. Koch, and W. Stolz,
Electron. Lett. 52, 1875 (2016).
Highly efficient electrical injection lasers in the near-infrared regime based on the type-II band alignment
in (GaIn)As/Ga(AsSb)/(GaIn)As single W'-quantum wells are realised. The structure is designed using
fully microscopic many-body theory, and characterised using electroluminescence measurements and broad-area
laser studies. A blue shift of 93 meV/(kA/cm2) is observed and compared with
theoretical investigations. Low threshold current densities of 0.4 kA/cm2, high differential
efficiencies of 66%, optical output powers of 1.4 W per facet, and internal losses of only 1.9/cm are observed
at a wavelength of 1164 nm for a cavity length of 930µm.
[69]
"Band offset in (Ga,In)As/Ga(As,Sb) heterostructures"
by: S. Gies, M.J Weseloh, C. Fuchs, W. Stolz, J. Hader, J.V. Moloney, S.W. Koch, and W. Heimbrodt,
J. Appl. Phys. 120, 204303 (2016).
A series of (Ga, In)As/GaAs/Ga(As, Sb) MQW heterostructures is analyzed using temperature-and power-dependent
PL spectroscopy. Pronounced PL variations with sample temperature are observed and analyzed using microscopic
many-body theory and band structure calculations based on the k.p method. The theory-experiment comparison
reveals an unusual, temperature dependent variation of the band alignment between the (Ga,In)As and Ga(As,Sb)
QWs.
[70]
"Gain spectroscopy of a type-II VECSEL chip"
by: C. Lammers, M. Stein, C. Berger, C. Moller, C. Fuchs, A.R. Perez, A. Rahimi-Iman, J. Hader, J.V. Moloney,
W. Stolz, S.W. Koch, and M. Koch,
Appl. Phys. Lett. 109, 232107 (2016).
Using optical pump-white light probe spectroscopy, the gain dynamics is investigated for a VECSEL containg
type-II GaAs/(GaIn) As/Ga(AsSb)/(GaIn) As/GaAs QWs.
Fully microscopic theory predicts a modal room temperature gain at a wavelength of 1170 nm, which is confirmed by the
experimental spectra. The results show a gain buildup on the type-II chip that is delayed relative to that of a type-I chip.
This slower gain dynamics is attributed to a diminished cooling rate arising from the reduced electron-hole scattering.
[71]
"Ultrafast non-equilibrium carrier dynamics in semiconductor laser
mode-locking"
by: J. Hader, M. Scheller, A. Laurain, I. Kilen, C. Baker, J.V. Moloney, and S.W. Koch,
Semicond. Sci. Technol. 32, 013002 (2017).
Experimental and theoretical results on the mode-locking dynamics in VECSEL are reviewed with an emphasis on
the role of nonequilibrium carrier effects. The theory consits of a fully microscopic many-body model for the
carrier distributions and polarizations, coupled to Maxwell's equations for the field propagation. Pump-probe
measurements are performed with (sub-) 100 fs resolution. The analysis shows how the nonequilibrium carrier
dynamics in the gain QWs and saturable absorbers significantly influences the resulting mode-locked pulses.
The microscopic model is used to determine the dependence of achievable pulse lengths and fluences on the
amounts of saturable and non-saturable losses and optical gain. The dependence of the pulse lengths on the
total amount of GDD is demonstrated experimentally. Theory-experiment comparisons are used to demonstrate the
highly quantitative accuracy of the fully microscopic modeling.
[72]
"Pulse interactions in a colliding pulse mode-locked vertical
external cavity surface emitting laser"
by: A. Laurain, R. Rockmore, H.T. Chan, J. Hader, S.W. Koch, A.R. Perez, W. Stolz, and J.V. Moloney,
J. Opt. Soc. America B - Opt. Phys. 34, 329 (2017).
A colliding pulse mode-locked VECSEL is demonstrated, generating pulses as short as 128 fs, with an average
power of 90 mW per beam and a repetition rate of 3.27 GHz.
The relevant laser parameters under different pumping regimes before and after the emergence of a side pulse
are then used as input parameters for the simulation of the pulse interactions in the saturable absorber.
A new comprehensive model for the calculation of saturable losses is presented. A study of the energy transfer
between the counter-propagating pulses shows that a colliding pulse scheme reduces the saturation fluence
by a factor 2.9.
[73]
"Fundamental transverse mode operation of a type-II
vertical-external-cavity surfaceemitting laser at 1.2µm"
by: C. Moller, F. Zhang, C. Fuchs, C. Berger, A. Rehn, A.R. Perez, A. Rahimi-Iman, J. Hader, M. Koch,
J.V. Moloney, S.W. Koch, and W. Stolz,
Electron. Lett. 53, 93 (2017).
The modal properties of a novel VECSEL with (GaIn)As/Ga(AsSb)/(GaIn)As type-II quantum wells are analysed.
The device, emitting at a wavelength around 1175 nm, is operated in TEM00 mode and optimised for a high beam quality.
The M-2 factors are measured at various pump powers. An excellent beam quality is observed for up to 350 mW with an
M-2 < 1.2.
[74]
"Non-equilibrium ultrashort pulse generation strategies in VECSELs"
by: I. Kilen, S.W. Koch, J. Hader, and J.V. Moloney,
Optica 4, 412 (2017).
We present the optimization of ultrashort mode-locked pulses in a VECSEL with a SESAM by modelling non-equilibrium quantum
dynamics of the electron-hole excitations in the semiconductor quantum-well gain and absorber medium via the semiconductor
Bloch equations and treating the field propagation at the level of Maxwell's wave equation. We introduce a systematic design
that predicts the generation of stable mode-locked pulses of duration less than twenty femtoseconds.
[75]
"An ab initio based approach to optical properties of semiconductor
heterostructures"
by: L.C. Bannow, P. Rosenow, P. Springer, E.W. Fischer, J. Hader, J.V. Moloney, R. Tonner, and S.W. Koch,
Model. Simu. Mat. Sci. Eng. 25, 065001 (2017).
A procedure is presented that combines DFT computations of bulk semiconductor alloys with the semiconductor Bloch
equations, in order to achieve an ab initio based prediction of the optical properties of semiconductor alloy
heterostructures. The parameters of an eight-band kp-Hamiltonian are fitted to the effective band structure of an
appropriate alloy. The envelope function approach is applied to model the QW. It is shown that Luttinger parameters
derived from band structures computed with the TB09 density functional reproduce extrapolated values.
The procedure is illustrated by computing the absorption spectra for a (AlGa)As/Ga(AsP)/(AlGa)As QW system with
varying phosphide content in the active layer.
[76]
"Valence band splitting in bulk dilute bismides"
by: L.C. Bannow, S.C. Badescu, J. Hader, J.V. Moloney, and S.W. Koch,
Appl. Phys. Lett. 111, 182103 (2018).
The band structure of bulk GaAs1-xBix systems for different atomic configurations and Bi
concentrations is calculated using DFT. The results show a Bi-induced splitting between the light-hole and heavy-hole
bands at the Gamma-point. We find a good agreement between our calculated splittings and experimental data.
The magnitude of the splitting strongly depends on the local arrangement of the Bi atoms but not on the
uni-directional lattice constant of the supercell. The additional influence of external strain due to epitaxial g
rowth on GaAs substrates is studied by fixing the in-plane lattice constants.
[77]
"High-temperature operation of electrical injection type-II (GaIn)As/Ga(AsSb)/(GaIn)As
"W"-quantum well lasers emitting at 1.3µm"
by: C. Fuchs, A. Bruggemann, M.J. Weseloh, C. Berger, C. Moller, S. Reinhard, J. Hader, J.V. Moloney, A. Baumner, S.W. Koch,
and W. Stolz,
Sci. Rep. 8, 1422 (2018).
Electrical injection lasers emitting in the 1.3µm wavelength regime based on (GaIn)As/Ga(AsSb)/(GaIn)As
type-II double "W"-QW grown on GaAs substrate are demonstrated. The structure is designed using fully
microscopic theory and fabricated using MOVPE. Laser emission
based on the fundamental type-II transition is demonstrated for a 975µm long laser bar in the temperature
range between 10 C and 100 C. The device exhibits a differential efficiency of 41 % and a threshold current
density of 1.0 kA/cm2 at room temperature with characteristic temperatures of T0 = 132 K
over the whole temperature range and T1 = 159 K between 10 C and 70 C and T1 =
40 K between 80 C and 100 C.
[78]
"Extended band anti-crossing model for dilute bismides"
by: J. Hader, S.C. Badescu, L.C. Bannow, J.V. Moloney, S.R. Johnson, and S.W. Koch,
Appl. Phys. Lett. 112, 062103 (2018).
Bandstructure properties of dilute bismide bulk systems are calculated using density functional theory.
An extended band anti-crossing model is introduced to fit the obtained results. Using these as inputs for a
fully microscopic many-body theory, absorption and photoluminescence spectra are computed for bulk and quantum-well
systems. Comparison to experimental results identifies the applicability range of the new anti-crossing model.
[79]
"Auger losses in dilute InAsBi"
by: J. Hader, S.C. Badescu, L.C. Bannow, J.V. Moloney, S.R. Johnson, and S.W. Koch,
Appl. Phys. Lett. 112, 192106 (2018).
Density functional theory is used to determine the electronic band structure and eigenstates of dilute
InAsBi bulk materials. The results serve as input for fully microscopic many-body models calculating the
composition and carrier density dependent losses due to Auger recombination. At low to intermediate carrier
concentrations, the Auger loss coefficients are found to be in the range of 10(-27) cm6/s for
Bi contents less than one percent and around 10(-25) cm6/s for compositions suitable for long-IR emission.
Due to the fact that in InAsBi the spin-orbit splitting is larger than the bandgap for all Bi-contents,
here, unlike in GaAsBi, an mostly exponential increase in the losses with the decreasing bandgap
is found for all compositions.
[80]
"VECSEL design for high peak power ultrashort mode-locked operation"
by: I. Kilen, S.W. Koch, J. Hader, and J.V. Moloney,
Appl. Phys. Lett. 112, 262105 (2018).
The generation of mode-locked pulses in VECSEL with a SESAM is studied by numerically solving the Maxwell
semiconductor Bloch equations describing the propagating light field coupled to the electron-hole-pair
excitations in the QWs. High peak-power sub-100 fs mode-locked pulses are realized through optimizing the
gain chip design. The unequal spacing of up to four QWs in a given field antinode leads to a broad linear
gain profile and reduced intracavity dispersion. The proposed designs are found to be robust with regard
to uncontrollable growth uncertainties.
[81]
"Modeling and experimental realization of modelocked VECSEL producing high power sub-100 fs pulses"
by: A. Laurain, I. Kilen, J. Hader, A.R. Perez, P. Ludewig, W. Stolz, S. Addamane, G. Balakrishnan, S.W. Koch, and J.V. Moloney,
Appl. Phys. Lett. 113, 121113 (2018).
A microscopic many-body theory driven design and optimization supports the experimental demonstration of
sub-100 fs pulse duration directly from a semiconductor laser. A passively modelocked vertical
external cavity surface emitting laser producing a pulse duration of 95 fs at a central wavelength
of 1025 nm is demonstrated. A stable colliding pulse modelocking regime with an output power of 90 mW per beam at a repetition rate of 2.2 GHz is achieved.
[82]
"Microscopic calculation of the optical properties and intrinsic losses in the methylammonium lead iodide perovskite system"
by: L.C. Bannow, J. Hader, J.V. Moloney, and S.W. Koch,
Appl. Phys. Lett. Materials 7, 011107 (2019).
Density functional theory is coupled to fully microscopic many-body models in order to calculate the absorption/gain, photoluminescence, and the optical and Auger losses in
methylammonium lead iodide perovskite. The excitonic properties of the material system are investigated and numerical results are presented for typical photo-voltaic operation
conditions and for the elevated carrier densities needed for laser operation.
)