Double-grating thin-film devices based on second-order Bragg interaction

Transverse mode of a dielectric film waveguide having periodic corrugations on the film-substrate interfaces and film-cover are described by the second-order Bragg interaction, derived from the four coupled-mode equations. Characteristics such as output coupler, input coupler and frequency-selective filter and distributed feedback layer features are also determined. Frequency selective radiation is obtained by the correct choice of the design-parameters implemented in the substrate.