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Numerical simulations of novel high-power high-brightness diode laser structures

: Boucke, K.; Rogg, J.; Kelemen, M.T.; Poprawe, R.; Weimann, G.


Arakawa, Y. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Physics and simulation of optoelectronic devices IX : 22 - 26 January 2001, San Jose, USA
Bellingham, WA: SPIE, 2001 (SPIE Proceedings Series 4283)
ISBN: 0-8194-3961-4
ISBN: 978-0-8194-3961-1
ISSN: 0277-786X
Conference "Physics and Simulation of Optoelectronic Devices" <9, 2001, San Jose/Calif.>
Fraunhofer ILT ()

One of the key topics in today's semiconductor laser development activities is to increase the brightness of high-power diode lasers. Although structures showing an increased brightness have been developed specific draw-backs of these structures lead to a still strong demand for investigation of alternative concepts. Especially for the investigation of basically novel structures easy-to-use and fast simulation tools are essential to avoid unnecessary, cost and time consuming experiments. A diode laser simulation tool based on finite difference representations of the Helmholtz equation in "wide-angle" approximation and the carrier diffusion equation has been developed. An optimized numerical algorithm leads to short execution times of a few seconds per resonator round-trip on a standard PC. After each round-trip characteristics like optical output power, beam profile and beam parameters are calculated. A graphical user interface allows online monitoring of the simulation results. The simulation tool is used to investigate a novel high-power, high-brightness diode laser structure, the so-called "Z-Structure". In this structure an increased brightness is achieved by reducing the divergency angle of the beam by angular filtering: The round trip path of the beam is two times folded using internal total reflection at surfaces defined by a small index step in the semiconductor material, forming a stretched "Z". The sharp decrease of the reflectivity for angles of incidence above the angle of total reflection leads to a narrowing of the angular spectrum of the beam. The simulations of the "Z-Structure" indicate an increase of the beam quality by a factor of five to ten compared to standard broad-area lasers.