COMPUTER-MODEL FOR TRANSIENT GRATING EXPERIMENTS AND ITS APPLICATION TO ANALYSIS OF LITAO3

A computer program is used to model transient grating experiments wher e two laser pulses induce a transient response in the sample and the t ime evolution of that response is monitored by the diffraction of a th ird pulse. The program is designed so that experimental conditions suc h as spot sizes, excitation angle, probe angle, relative pump and prob e positions, and laser wavelength can be readily varied. The model acc ommodates acoustic and polariton excitations which travel significant distances during an experiment. This program is used to simulate and a nalyze transient grating experiments of A(1)-symmetry polaritons in th e ferroelectric crystal LiTaO3. Previous experiments have used two dif ferent detection schemes for the scattered pulse, and two different mo dels for the optic modes of LiTaO3 were proposed. The simulations show that the discrepancies result from an experimental artifact in the he terodyne detection experiments, and both sets of experiments are consi stent with one model for the crystal's optic modes.