Theory of transient energy transfer in gallium arsenide

Numerical calculations are given for optical two-beam coupling in undoped, semi-insulating GaAs using picosecond pulses. Absorption at the intrinsic defect EL2, two-photon absorption, free-carrier absorption, photorefractive gratings, free-carrier gratings, and absorption gratings are included. Results for normalized probe transmission as a function of pump fluence and as a function of pump-probe delay show that the major effects are energy transfer from pump to probe or from probe to pump (depending on crystal orientation) due to the photorefractive effect, two-photon absorption, and free-carrier transient energy transfer from the pump to the probe.