[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 Al_xGa_1-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.




[27]
"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).


[28]
"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).


[29]
"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).


[30]
"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).


[31]
"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.


[32]
"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.



[33]
"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.


[34]
"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).


[35]
"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.


[35]
"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.