Bleaching and Spectral Shape Modification of CdS Photocurrent due to He–Ne Laser Pumping

The influence of He-Ne laser pumping on the photocurrent of a CdS single crystal was studied in the range 450–700 nm at room temperature. It was observed that the photocurrent was extremely dependent on laser irradiation. A low pump intensity of 64 mWcm-2 quenches the photocurrent by more than three orders of magnitude. The pumping also induces a spectral shape modification, i.e., a reduction of the gap photoconductivity at 500 nm below the photocurrent due to trap levels at 540 nm. The phenomena are explained in terms of two-photon absorption.