Optical detection near absorption band edge

The optical detection of the frequencies of incident radiation close to the fundamental frequencies of nonlinear crystals was investigated in the specific case of semiconductors CdS and CdSe. The experimental results were used to calculate the components of the nonlinear susceptibility tensor X⁰₃₃₃ and X⁰₃₁₁ of CdS and CdSe at the frequencies of ruby and neodymium lasers. Anomalously high susceptibilities were obtained for CdSe. The phenomenon of saturation of optical detection was observed for the first time and investigated. A comparison with earlier experimental results indicated that the saturation was of the same nature as the bleaching effect.