Diffraction emission of surface waves from diffused optical waveguides with a harmonically modulated permittivity

An analysis is made of the emission of H and E waves in the first diffraction order from a diffused waveguide where the permittivity is harmonically modulated along the waveguide and the transverse distribution is arbitrary (for an arbitrary angle of incidence of surface waves on a volume grating). It is shown that if the relative transverse distributions of the permittivity increment in the waveguide layer and its modulation amplitude are the same, the coefficients of diffraction attenuation of the surface waves can be expressed in a closed analytic form in terms of the parameters of a weak diffused periodic waveguide.