Photoinduced nonlinear optical phenomena in Sb2Se3-BaCl2-SnCl2 glasses

Photoinduced nonlinear optical phenomena have been studied in amorphous Sb2 Te3-CaCl2-SnCl2 glasses using photoinduced optical second harmonic generati on (SHG). The photoinduced SHG signal was measured for double frequency of a CO2 laser (lambda = 5.3 mu m) using a photoinducing CO laser (lambda = 5. 5 mu m). We have found that the SHG signal intensity increases with increas e of the CO laser photoinducing exposure and achieves its maximum value aft er 1.5 h. Absolute values of the SHG signals were more than one order in ma gnitude smaller comparing to a chi(222) tensor component for the ZnSe singl e crystals. The SHG signal strongly increases if temperature decreases from 39 to 16 K. Femtosecond probe-pump measurements indicate existence of the SHG maximum at pump-probe time delay of about 43 ps. It is suggested that S b-Se tetrahedra play a key role in the observed photoinduced nonlinear opti cal effects. Degree of noncentrosymmetry of corresponding bonds depends on time of the CO-laser illumination, temperature and mechanical stresses. Sim ultaneously, the investigated glasses can serve as promising materials for a femtosecond IR quantum electronics. (C) 2000 Kluwer Academic Publishers.