Optical properties, bistability, and nonlinearity of evaporated ternary II-VI semiconductor thin films

Abstract

Phone 7-0122-7695 15, Fax 7-0122-223563, Telex 261212 VU SU Ternary Il-VI-semiconductors like CdSSei-or ZnCdi-S were prepared by thermal evaporation of binary semiconductors from a double source. The influence of substrate temperature during thin film deposition and of thermal annealing in argon atmosphere on absorption edge steepness is studied. A high absorption edge steepness is advantageous to achieve large resonant optical nonlinearities, like absorption bistability and electronic nonlineanties. The position of the absorption edge can be tuned by choosing a proper film composition. Thermally induced optical bistability is demonstrated. Electronic nonlinearities are investigated in ns-and ps-pump-probe experiments. Fast bleaching with <60 ps relaxation time is observed at the absorption edge. The maximum bleaching coefficient for CdSo.695eo.31 films is 1.4 cmlkW at X =587 nm for pumping with 2. = 377 nm. Annealing the films showed no effect on the relaxation time, but the bleaching coefficient was increased by a factor of five.