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Response of GaAs to fast intense laser pulses J. S. Graves and R. E. Allen

Summary: Response of GaAs to fast intense laser pulses
J. S. Graves and R. E. Allen
Department of Physics, Texas A&M University, College Station, Texas 77843-4242
Received 4 May 1998
Motivated by recent experiments, we have performed simulations which show in detail how the electrons
and ions in GaAs respond to fast intense laser pulses with durations of order 100 fs and intensities of order
1 10 TW/cm2
). The method of tight-binding electron-ion dynamics is used, in which an arbitrarily strong
radiation field is included through a time-dependent Peierls substitution. The population of excited electrons,
the atomic displacements, the atomic pair-correlation function, the band structure, and the imaginary part of the
dielectric function are all calculated as functions of time, during and after application of each pulse. Above a
threshold intensity, which results in promotion of about 10% of the electrons to the conduction band, the lattice
is destabilized and the band gap collapses to zero. This is most clearly revealed in the dielectric function ( ),
which exhibits metallic behavior and loses its structural features after 100200 fs.
S0163-1829 98 01843-8
There are two distinct mechanisms through which an in-
tense laser pulse can destabilize the structure of a molecule
or material: On a relatively long time scale ( 1 ps), the
energy of excited electrons can be transferred to thermal mo-


Source: Allen, Roland E. - Department of Physics and Astronomy, Texas A&M University


Collections: Physics