Second-harmonic generation in polycrystalline ZnSe in the absence of phase matching.

The work is devoted to the study of the second-harmonic generation (SHG) process as a result of random quasi-phase-matching of thulium laser radiation in ZnSe polycrystals. A linear dependence of the SHG efficiency on the nonlinear medium length has been observed in the experiment. The efficiencies of SHG in ZnSe polycrystals with average grain sizes from 35 μ m to 380 μ m were compared. The obtained results are in good agreement with the theory in the case of a Gaussian grain size distribution. [ABSTRACT FROM AUTHOR]