Analytical study of new patterns of the surface waves in a photorefractive crystal covered with a gradient guiding layer with the spatially reducing refractive index

Abstract New types of surface waves and the influence of optical parameters and temperature on their properties are analytically studied. Wave propagation along the surface of a photorefractive crystal with diffusion-type nonlinearity coated with a guiding layer with the refractive index gradient is considered. The refractive index is characterized by a monotonic decrease with a distance from the crystal surface into the depth of the guiding layer. Exact analytical solutions to the formulated equations describing two new types of surface waves with unique properties in the system under consideration are found. It is specified how the optical characteristics and temperature can influence on the properties of surface waves of both types based on the obtained solutions. It is enough to vary the temperature if it is necessary to change the wave properties only in a photorefractive crystal but in the layer so that they remain unchanged. In this case, for the oscillation frequency will change the waves of the first type and the depth of field penetration into the photorefractive crystal will change for both types of waves. It is necessary to the angle of incidence of the beam exciting the surface wave and the optical parameters of the refractive index profile of the gradient guiding layer to change the properties of the field distribution. The explicit expressions of power flows are obtained, using of which features of the spatial distribution of the energy density of surface waves between the crystal and the covering gradient guiding are established. The ways to control this distribution of surface wave energy density by varying optical parameters and temperature are identified.