Influence of self-focusing on laser damage to II-VI semiconductors

An investigation was made of the nature and magnitude of the threshold of damage caused by ruby and neodymium laser radiation to CdS_xSe_1–x and Zn_xCd_1–xS semiconductors with a range of forbidden band widths. Surface and bulk damage was observed depending on the ratio of the forbidden band width to the laser photon energy. The surface damage involved the absorption of part of the laser radiation energy, which resulted in heating and melting of the semiconductor. The bulk damage started from self-focusing, which was the limiting factor governing the optical strength of the semiconductor. Electron avalanche ionization was a likely mechanism of the bulk damage.