BLEACHING AND INDUCED ABSORPTION KINETICS IN CUINS2XSE2(1-X)-DOPED GLASSES SUBJECTED TO PICOSECOND EXCITATION

Transmission and absorption kinetics was studied in glasses doped with CuInS2xSe2(1-x) microcrystals as a function of 15-ps exciting pulses with wavelengths of 1.08 and 0.54 mum. At low excitation intensities a pproximately 50 MW/cm2 the bleaching effect with recovery time approxi mately 11 ps was observed for the photon energies slightly exceeding t he bandgap. The bleaching was assumed to result from the filling of qu antum-well levels in CuInS2xSe2(1-x) microcrystals. As the pump intens ity grew, a fast (approximately 40 ps) transition from bleaching to st rong induced absorption with relaxation time approximately 4 ns was ob served, which was attributed to two-photon interzonal transitions. At high pump intensities (approximately 10 GW/cm2) only induced absorptio n was noticed. Bleaching did not occur when the photon energy substant ially exceeded the bandgap; the growing pump level led to an appearanc e of induced absorption. The parameter of two-photon absorption has be en estimated for CuInS2xSe2(1-x)-doped glasses at a wavelength of 1.08 mum. Application of the investigated glasses for mode locking of puls ed YAG:Nd and YAlO3:Nd lasers made it possible to obtain ultrashort pu lses respectively 38 and 16 ps long.