A new optical method for measuring the optical activity of crystals is developed. Temperature dependence of gyration component g_{11} of ferroelectric lead germanate is measured. The obtained results confirm that lead germanate may be considered as a gyroelectric crystal.
The article presents the experimental results of the investigation of the absorption spectra and nonlinear refraction of the metal-dielectric nanocomposite that contains the lithium niobate pyroelectric crystal coated with the silver nanofilms on its surface. The atomic force microscopy surface research of these crystals with and without films are also provided. The nanowidth silver films impact on optical spectra and nonlinear refraction of LiNbO₃-Ag nanocomposite was analyzed depending on the sign of the side charge of the crystal, that contain nanofilms.