Influence of the domain structure of LaBGeO₅ polar crystals on their gyrotropic properties

The spectra of transmission coefficients and absorption indices of monodomain and polydomain LaBGeO₅ samples were measured. It is shown that for a more accurate measurement of the rotation of the plane of polarization of light, it is necessary to use the transmission coefficient spectra not only for parallel and crossed polarizers, but also at other angles between them. The obtained values of p for both samples are described quite well by a single variance using the Drude formula. This is consistent with the fact that the value of p should not change with monodomenization of the crystal at a given symmetry (P31 in the ferroelectric phase and P3121 in the paraelectric phase). It is shown that the generation of the second harmonic of the Cherenkov type is observed only in a polydomain sample, while the radiation of the second harmonic is not polarized. The domain structure of the samples was observed by scanning electron microscopy and piezoelectric force microscopy. For a polydomain sample, the presence of a labyrinthine domain structure was shown, for a monodomain sample, no contrast changes were observed within the scanning area.