NANOSECOND 4-WAVE-MIXING IN SEMIINSULATING GAAS

Dynamic gratings of free carriers are generated from optical excitation, with nanosecond pulses, of the deep EL2 level in semi-insulating gallium arsenide. The photogenerated holes and electrons change the plasma frequency of the sample producing a nonlinear modification of its index of refraction. This effect is evidenced by a degenerate four-wave mixing experiment. In regards to the sample parameters, a fair agreement is obtained between the experimental values and the theoretical predictions derived from of the Drude-Lorentz model and the anharmonic motion of carriers.