Guided-wave couplers and amplifier based on the second-order Bragg interaction

Guided radiated wave coupling by means of a second-order surface relief grating etched onto a thin-film optical waveguide is investigated for the transverse magnetic mode. The necessary governing equations derived from a quasi-optic analysis are summarized. The quasi-optic analysis is an asymptotically exact perturbation procedure that is valid, in particular, for amplitudes of the grating that are small relative to the film thickness. The interference effect in the guided waves is employed to deduce the design criteria for optimizing the performance of the output and the input couplers, the frequency-selective reflector, and the surface-emitting amplifier. The device characteristics are found to be insensitive to small changes in the physical parameters about their designed values.