Flexoelectric contribution to the perturbation of optical properties in nanostructured single-crystals

Stanislav M. Shandarov, Nikolay I. Burimov, Arkady E. Mandel’, Alexander E. Urban, Anna A. Shmidt, Andrei O. Zlobin, Vasiliy V. Shepelevich and Konstantin Shcherbin

State University of Control Systems and Radioelectronic, Russia

The additional contributions of converse flexoelectric effect to the periodical perturbations of the light-frequency dielectric tensor, which are induced by reflection grating in photorefractive crystals as well as by domain structure in ferroelectric ones are considered. We review the general equations for elastic fields of reflection grating, which are due to converse piezoelectric and flexoelectric effects in a photorefractive crystal. Within the approximation of the absence of spatial dispersion the analytical expressions for components of elastic-strain tensor for such fields in the crystals with arbitrary orientation are derived. Because of the linear electro-optic and elasto-optic effects the electric and elastic fields of the grating induce the perturbations of the components of the dielectric tensor at the frequency of the light wave. It is shown that the spatial shift of the perturbation distribution, which is due to flexoelectric effect, is 0 or 180 degree with respect to the interference fringes, while it is well known that such shift is +90 or -90 degree for electro-optic component. Because of that we revealed the flexoelectric contribution to the photorefractive response from electro-optic one in the (100)- and (111)-cut cubic photorefractive crystals BTO, BSO and CdTe in experiments utilizing the contradirectional interaction between a strong stationary reference wave and a weak phase-modulated signal wave on reflection grating of the diffusion type. The flexoelectric contribution to the linear diffraction of light beam on the periodic domain structures in lithium niobate crystal is also discussed.