Enhancement of second-harmonic generation in zinc selenide by crystal defects

Abstract
Tunable radiation in the 0.43–0.52‐μm spectral region was produced by frequency doubling a tunable dye laser in ZnSe. At wavelengths shorter than the band gap of ZnSe (λ<0.46 μm), second‐harmonic power was limited by crystal absorption, whereas for longer wavelengths the second‐harmonic power was as much as 1500 times larger than that predicted for a single‐domain crystal. This enhancement is predicted by a simple theory which accounts for the favorable nonlinear optical effects of rotational twins and crystal defects.