Enhanced Photorefractive Gain in the Bulk Semiconductors GaAs:EL2 and CdTe:V on a 5 psec Timescale

Abstract

Recently, we reported extensive measurements of the energy transfer, via the photo-refractive effect and transient energy transfer, in picosecond two-beam coupling experiments in semiinsulating GaAs:EL2.1 In that case, 30 psec pulses from an active-passive mode-locked and Q-switched Nd:YAG laser system were used to generate a grating with a period of 1.7 µm in the semiconductor. That experiment was conducted in a regime where the laser pulse duration is an order of magnitude larger than the time required for the electrons to diffuse one grating period in the conduction band. Under these conditions, the two-beam coupling geometry was successfully modelled using a numerical solution (with no free parameters) to the equations describing the freecarrier dynamics and nonlinear material response of GaAs:EL2 during the optical interaction. Similar agreement between the theory and experimental data was obtained for the doped semiconductors CdTe:V and InP:Fe.