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The fading of the phase conjugation efficiency and luminescence quantum yield in CdSxSe1−x-doped glasses was investigated as a function of laser exposure using pulsed and cw mode-locked lasers. An analysis of the kinetics of the photodarkening effect is presented. The rate constant of the fading process depends nonlinearly upon the laser fluence and is sensitive to the origin of the glass.

We present simultaneous efficient second-͑SHG͒ and third-harmonic generation ͑THG͒ in a single periodically-poled KTP waveguided crystal pumped by a compact femtosecond Yb-based laser in a condition of exactly phase-matched frequency doubling and nonphase-matched sum-frequency mixing processes. Internal conversion efficiency as high as 33% for SHG ͑532 nm͒ and ϳ2% for the cascaded THG ͑355 nm͒ is reported. We believe this to be a clear experimental demonstration that strong third-harmonic can be generated in frequency doubling crystals through a nonphase-matched sum-frequency mixing process.

It is shown experimentally that deviations from the square dependence of the phase-conjugate reflectivity in CdSxSel-doped glasses on the reduced pump power can be explained by the dependence of the relaxation time of the induced optical nonlinearity on intensity. The same argument explains the diversity of several previously published results. Nonlinear-optical properties of semiconductor-doped glasses have been extensively investigated by four-wave mixingl-7

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