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Summary: Time Evolution of Second Order Susceptibility in GaAs following a
Fast Intense Laser Pulse
T. Dumitrica and R.E. Allen
Department of Physics, Texas A&M University,
College Station, Texas 77843, USA
Abstract
Using the technique of tight-binding electron-ion dynamics, we have calculated the
evolution of the nonlinear susceptibility (2)() in GaAs during the first few hundred
femtoseconds following an ultrafast and ultra-intense laser pulse. Above a threshold
fluence, our simulations show that (2)() drops to zero, in agreement with the exper-
imental measurements. The results indicate a rapid nonthermal transition from the
original tetrahedral structure to a disordered structure, and support the conclusion
that structural changes following ultrashort pulses are a direct consequence of bond
destabilization.
1 Introduction
The transformations that occur in a semiconductor subjected to intense laser radiation are
of considerable interest, because one would like to understand the fundamental physical
processes in the newly accessible regime of short time scales and high intensities. There
have consequently been a number of previous experimental observations [1-5] and theoretical
calculations [6, 7] of the behavior of semiconductors following ultrashort and ultra-intense
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