Light-beam propagation at planar thin-film nonlinear waveguides

The light-beam scattering at a symmetric dielectrical waveguide formed by two interfaces between three nonlinear focusing media is considered analytically and numerically. The problem of beam transmission and reflection is effectively analyzed in the framework of the so-called equivalent-particle theory. It is shown also that the beam scattering may be accompanied by a strong emission of radiation which is not taken into account by the equivalent-particle approximation. Radiative losses of the scattering beam are calculated, and the applicability limits of the equivalent-particle approach are discussed by making a comparison between numerical and analytical results. In particular, it is shown that the incident beam may be captured by the thin-film waveguide to form a surface wave, due to radiation-induced losses.