A protrusion in the absorption spectra of GaAs excited by high-power picosecond light pulses

Abstract

Absorption spectra of GaAs excited by short high-power light pulses are calculated. The appearance of a “protrusion” in the spectra is caused by the deviation of the electron distribution function from the Fermi function. The distortion of the distribution function is related to LO phonon-assisted relaxation of electrons between the states involved in the formation of a “hole” in the gain region and a “protrusion” in the absorption region. It is shown that the temperature of optical phonons responsible for the relaxation of photoexcited electrons differs from the lattice temperature and the time of recovery of the perturbed Fermi distribution via electron-electron collisions is nearly equal to the characteristic time of interaction between electrons and optical phonons.