Optical quality and efficiency of nonlinear laser crystals

Correlation between non-linear properties and optical quality of KTP crystals is investigated. Optical quality is investigated by the Schlieren method. The distribution of the mean-root-square refractive index gradient has been obtained along the radiation propagation direction. A comparison of optical quality of a crystal and the conversion efficiency is made. For the first time, the possibility of domain structure imaging in a crystal by using only an optical method is shown.