NASA Technical Reports Server (NTRS) : Computational pdf

NASA Technical Reports Server (NTRS) : Computational

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The main objective of the Joint-Research Interchange NCC2-5149 was to develop computer codes for accurate simulation of femtosecond pulse propagation in semiconductor lasers and semiconductor amplifiers [I]. The code should take into account all relevant processes such as the interband and intraband carrier relaxation mechanisms and the many-body effects arising from the Coulomb interaction among charge carriers [2]. This objective was fully accomplished. We made use of a previously developed algorithm developed at NASA Ames [3]-[5]. The new algorithm was tested on several problems of practical importance. One such problem was related to the amplification of femtosecond optical pulses in semiconductors. These results were presented in several international conferences over a period of three years. With the help of a postdoctoral fellow, we also investigated the origin of instabilities that can lead to the formation of femtosecond pulses in different kinds of lasers. We analyzed the occurrence of absolute instabilities in lasers that contain a dispersive host material with third-order nonlinearities.

Starting from the Maxwell-Bloch equations, we derived general multimode equations to distinguish between convective and absolute instabilities. We find that both self-phase modulation and intensity-dependent absorption can dramatically affect the absolute stability of such lasers. In particular, the self-pulsing threshold (the so-called second laser threshold) can occur at few times the first laser threshold even in good-cavity lasers for which no self-pulsing occurs in the absence of intensity-dependent absorption. These results were presented in an international conference and published in the form of two papers

• Creator/s: NASA Technical Reports Server (NTRS
• Date: 1/1/1998
• Year: 1998
• Book Topics/Themes: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMS, PULSED LASERS, SEMICONDUCTORS (MATERIALS), SEMICONDUCTOR LASERS, AMPLIFICATION, ELECTROMAGNETIC PULSES, PHASE MODULATION, MAXWELL EQUATION, MANY BODY PROBLEM, LASER CAVITIES, Agrawal, Govind P., Goorjian, Peter M

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