Fast and slow light observation at laser pulse interaction with contrast structures induced in semiconductor due to its nonlinear absorption and optical beam diffraction

摘要

We analyze laser pulse propagation in a semiconductor with nonlinear absorption depending on free electron concentration and a concentration of ionized donors. Under certain conditions this interaction is accompanied by a resonator-less optical bistability appearance. It is an attractive modern problem because of developing the all-optical methods for data treatment. In contrast to many investigations made early we take into account a longitudinal diffraction of the optical beam. It means that we consider optical beam diffraction along coordinate of its propagation. This results in the presence of the optical radiation reflection from spatio-temporal contrast structure induced by the laser pulse. As a result, we observe a propagation of the fast light corresponding to wave reflected from a semiconductor as well as unmoving part of the pulse placed near the semiconductor face. The reflection of laser pulse from the boundary of high absorption domain is demonstrated. This phenomenon takes place due to presence of high gradient of optical properties of a medium.