Propagation of surface waves along a boundary of a photorefractive crystal with a nonlinear defocusing coating

A composite waveguide structure is considered; it is a crystal with the diffusion mechanism of formation of a nonlinear photorefractive response, on the surface of which a coating with defocusing Kerr nonlinearity is deposited. It is shown that nonlinear surface extraordinary waves of two types (with different ranges of existence and field decay profiles) exist in it. The modes of nonlinear surface wave propagation, at which the field intensity can be maximum or minimum near the surface or at the crystal–coating interface, are determined.