SPATIAL AND TEMPORAL BEAM RESHAPING EFFECTS USING BULK CDTE

Reshaping effects of ns pulses were theoretically and experimentally investigated using bulk CdTe. The experiments were performed using a 1.064 mu m Nd:YAG laser with pulse duration of 10 ns. We observed that the laser pulses emerging from the sample experienced temporal compression and modulation which were found to be dependent on the input irradiance, the distance from the exit surface of the sample, and the cross sectional area detected. Self-defocusing and the formation of ring structures were also observed in the transmitted spatial profile and were found to be dependent on the input irradiance and the position of the detector from the sample. In our model we assumed that the free carriers generated by the two-photon absorption process were responsible for the induced nonlinear change in the index of refraction. As a result, the temporally and radially dependent phase shift encoded to the held that emerged from the sample was the cause of the reshaping effect. The results of our model, for both the spatial and the temporal profiles, are in good agreement with the experimental results. Moreover, the nonlinear parameters deduced from the fitting are in good agreement with previous experimental and theoretical results. (C) 1995 American Institute of Physics.