Abstract

It is well-known that II-VI semiconductors—in particular CdS—exhibit photothermally induced all-optical bistabilities (all-OBs) under excitations with appropriate laser beams.^1,2 For the first time, we have studied the spatial modification of the focus of the 514.5 nm argon laser line during all-OBs of a CdS crystal. We observed that the laser beam is split into two beams after the bistable switch in the initial focus has taken place. A schematic sketch of the effect observed and its application as an all-optical pulse generator is shown in Figs. 1(a) and (b), respectively. A slit was placed about 30 cm behind the CdS crystal on the side of the transmitted beam of the 514.5 nm line. At a certain threshold of the incident power the sample exhibits reversible photodarkening and the straight transmitted beam disappears in a bistable manner and two beams move out of the focus as depicted in Fig. 1(b) whereas beam 1 induces the light pulse shown in Fig. 2.

© 1995 IEEE