8,533 research outputs found

    Modeling and simulations of beam stabilization in edge-emitting broad area semiconductor devices

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    A 2+1 dimensional PDE traveling wave model describing spatial-lateral dynamics of edge-emitting broad area semiconductor devices is considered. A numerical scheme based on a split-step Fourier method is presented and implemented on a parallel compute cluster. Simulations of the model equations are used for optimizing of existing devices with respect to the emitted beam quality, as well as for creating and testing of novel device design concept

    Modeling and simulations of beam stabilization in edge-emitting broad area semiconductor devices

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    A 2+1 dimensional PDE traveling wave model describing spatial-lateral dynamics of edge-emitting broad area semiconductor devices is considered. A numerical scheme based on a split-step Fourier method is presented and implemented on a parallel compute cluster. Simulations of the model equations are used for optimizing of existing devices with respect to the emitted beam quality, as well as for creating and testing of novel device design concept

    Theory and simulation of subwavelength high contrast gratings and their applications in vertical-cavity surface-emitting laser devices

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    This work intends to fully explore the qualities and applications of subwavelength gratings. Subwavelength gratings are diffraction gratings with physical dimensions less than the wavelength of incident light. It has been found that by tailoring specific dimension parameters, a number of different reflection profiles can be attained by these structures including high reflectivity or low reflectivity with broad and narrow spectral responses. In the course of this thesis the physical basis for this phenomenon will be presented as well as a mathematical derivation. After discussion of the mechanics of the reflection behavior, the methods used in modeling subwavelength gratings and designing them for specific functions will be explored. Following this, the fundamentals of vertical-cavity surface-emitting lasers (VCSELs) will be discussed, and the applications of subwavelength gratings when used with these lasers will follow. Several devices, both theoretical proposals and fabricated examples, will be presented in addition to the available performance measurements. Finally, the fabrication challenges that restrict subwavelength gratings from adoption as standard components in VCSEL design will be considered with regard to ongoing fabrication research

    Modeling and efficient simulations of broad-area edge-emitting semiconductor lasers and amplifiers

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    We present a (2+1)-dimensional partial differential equation model for spatial-lateral dynamics of edge-emitting broad-area semiconductor devices and several extensions of this model describing different physical effects. MPI-based parallelization of the resulting middlesize numerical problem is implemented and tested on the blade cluster and separate multi-core computers at the Weierstrass Institute in Berlin. It was found, that an application of 25-30 parallel processes on all considered platforms was guaranteeing a nearly optimal performance of the algorithm with the speedup around 20-25 and the efficiency of 0.7-0.8. It was also shown, that a simultaneous usage of several in-house available multi-core computers allows a further increase of the speedup without a significant loss of the efficiency. Finally, an importance of the considered problem and the efficient numerical simulations of this problem were illustrated by a few examples occurring in real world applications

    Integrated electroplated heat spreaders for high power semiconductor lasers

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    Thermal management of high power semiconductor lasers is challenging due to the low thermal conductivity of the laser substrate and the active device layers. In this work, we demonstrate the use of a microfabricated laser test device to study the thermal management of edge emitting semiconductor lasers. In this device, metallic heat spreaders of high thermal conductivity are directly electroplated on structures that mimic edge-emitting semiconductor lasers. The effects of various structural parameters of the heat spreader on the reduction of the thermal resistance of the laser test device are demonstrated both experimentally and theoretically. Without resolving to computational costive simulations, we developed two independent analytical models to verify the experimental data and further utilized them to identify the dominant thermal resistance under different laser mounting configurations. We believe our approach here of using microfabricated devices to mimic thermal characteristics of lasers as well as the developed analytical models for calculating the laser thermal resistance under different mounting configurations can potentially become valuable tools for thermal management of high power semiconductor lasers

    Modeling and efficient simulations of broad-area edge-emitting semiconductor lasers and amplifiers

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    We present a (2+1)-dimensional partial differential equation model for spatial-lateral dynamics of edge-emitting broad-area semiconductor devices and several extensions of this model describing different physical effects. MPI-based parallelization of the resulting middlesize numerical problem is implemented and tested on the blade cluster and separate multi-core computers at the Weierstrass Institute in Berlin. It was found, that an application of 25-30 parallel processes on all considered platforms was guaranteeing a nearly optimal performance of the algorithm with the speedup around 20-25 and the efficiency of 0.7-0.8. It was also shown, that a simultaneous usage of several in-house available multi-core computers allows a further increase of the speedup without a significant loss of the efficiency. Finally, an importance of the considered problem and the efficient numerical simulations of this problem were illustrated by a few examples occurring in real world applications

    Efficient coupling of inhomogeneous current spreading and dynamic electro-optical models for broad-area edge-emitting semiconductor devices

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    We extend a 2 (space) + 1 (time)-dimensional traveling wave model for broad-area edge-emitting semiconductor lasers by a model for inhomogeneous current spreading from the contact to the active zone of the laser. To speedup the performance of the device simulations, we suggest and discuss several approximations of the inhomogeneous current density in the active zone

    Numerical analysis of the frequency chirp in quantum dot semiconductor lasers

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    We present a numerical model for the analysis of the chirp dynamics of quantum-dot (QD) semiconductor laser under large signal current modulation. The model is based on the multi-population rate equation formalism, and it includes all the peculiar characteristics of the active QD material such as the inhomogeneous broadening of the gain spectrum, the presence of an excited state confined in the QDs and the presence of nonconfined states due to the wetting layer and the barrier. In this paper the model is applied to the analysis of the chirp of two,QD single-mode lasers emitting from the ground state and from the excited state, respectively. In order to make comparisons of the chirp in various operating conditions, we define some equivalent parameters for quantifying the adiabatic and transient contributions to the chirp. These parameters,are then used to analyze the chirp as function of the bias current, of the modulation depth and of the modulation frequency. All the various simulation results show that the carrier accumulation in the QD states, poorly involved in the stimulated emission process and the carrier dynamics in these states, can cause a nonzero chirp under current modulation even for the ideal condition of zero linewidth enhancement factor (or alpha-parameter) at the laser threshol
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