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IR-induced second-harmonic generation in PbSe microcrystallites

The IR-induced second-harmonic generation in PbSe microcrystallites with sizes of 10–30 nm is observed for the first time. A phenomenological approach of the IR picosecond nonlinear optical response in PbSe is developed for the middle-IR spectral range (5–15 µm). A model reproducing the basic features of experimental data related to second-order optical nonlinearity caused by photoinduced electron–phonon anharmonic interactions is proposed. The model is based on the band structure calculations and photoinduced kinetics with account taken of electron–phonon anharmonic interactions.