Light-induced transmission nonlinearities in gallium selenide

Abstract

A transmission nonlinearity is reported which consists of a change in the He-Ne probe beam intensity transmitted by GaSe samples in response to a 7.8 ns Nd:YAG laser beam incident pulse. The transmission transients are due to an excitonic screening by the pump photogenerated carriers, which leads to absorptive bleaching and refractive index reduction. The absorption decrement was calculated using the Banyai and Koch semiphenomenological model which incorporates a screened Coulomb potential, a gap renormalization, and a band filling term, with the carrier density as a parameter. The mechanisms behind the transmission nonlinearity are defined.