Optical processes in thin-film lasers and waveguides with arbitrary distributions of the refractive index

A theory is developed of planar waveguide systems with arbitrary transverse distributions of the refractive index. This theory describes the diffraction-caused conversion of surface waves into other surface waves as well as the emission of waves in the case when one of the boundaries between the dielectric layers forming a waveguide is characterized by a weak sinusoidal modulation. The theory deals with the first- and second order diffraction processes. A detailed analysis is made of the diffraction-induced emission of H and E surface waves and of the resonant mutual conversion of these waves in the first diffraction order. In particular, the conditions for the generation of H and E waves are formulated for thin-film lasers with distributed feedback and arbitrary transverse distributions of the refractive index.