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Proceedings Paper

Determination of photoionization cross sections, diffusion lengths, and deep-level concentrations in semi-insulating InP and GaAs through energy-transfer measurements
Author(s): Philippe Delaye; Gerald Roosen
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Paper Abstract

optical wave mixing in nonlinear media such as photorefractive crystals, semiconductors and liquid crystals have been vigorously studied in the past few years (1-4). Such researches are motived either by potential applications like amplification and phase conjugation, or by investigation on the physics of such effects. Here we report on the generation of conjugate wavefronts by degenerate forward and backward four wave mixing in some GaAs samples. We perform our experiment with a Nd-YAG laser emitting pulses of eight nanosecond duration. The semi-insulating GaAs sample used exhibits a large concentration of EL2 defects which present a good photoionisation cross section at 1.06 micron. The nonlinearity we observed is due to a hole and electron grating photogenerated from the EL2 defects. This is quite different from direct band to band absorption. Indeed, the hole and electron distributions are coupled through the concentration of ionized EL2+ and neutral EL2° defect. Nevertheless, as we will show,at high energy the densities of free electrons and holes tend to be equal due to an evolution of the respective concentration of EL2+ and EL20. This plasma of holes and electrons modifies the plasma frequency. The modulation of the index is then derived from the DrUde Lorentz model. We first present our experimental results .We show that most of them can be explained by the kinetics of the carriers photogenerated from deep levels. Analytical and numerical results are presented. From the numerical simulation, with these numerical results and semi analytical solutions of the wave propagation equations, one then predicts the reflectivity of our multiwave mixing experiment.

Paper Details

Date Published: 1 August 1990
PDF: 8 pages
Proc. SPIE 1273, Nonlinear Optical Materials III, (1 August 1990); doi: 10.1117/12.20461
Show Author Affiliations
Philippe Delaye, Institut d'Optique Theorique et Appliquee (France)
Gerald Roosen, Institut d'Optique Theorique et Appliquee/CNRS (France)


Published in SPIE Proceedings Vol. 1273:
Nonlinear Optical Materials III
Peter Guenter, Editor(s)

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