Optical hysteresis and light absorption in a-As/sub 2/S/sub 3/ and c-As/sub 2/S/sub 3

Results of the experimental investigations of nonlinear absorption of laser pulses in amorphous a-As/sub 2/S/sub 3/ films are presented. The optical transmission hysteresis and reversible film photodarkening at interband excitation of a-As/sub 2/S/sub 3/ films in a blue-green spectral region is reported for the first time. It was suggested that the nonlinear light absorption could be explained by taking into account the light interaction with nonequilibrium localized lattice vibrations anharmonically coupled with the extended phonons. The measurements of peculiarities of the pulse absorption in crystalline c-As/sub 2/S/sub 3/ films can confirm the proposed explanation.