Higher-order Bragg diffraction by a periodic structure in a planar optical waveguide

An analysis is made of the higher-order Bragg diffraction by grating structures with a period Λ in planar optical waveguides. It is shown that effectively the diffraction is of the first order by a grating with a period Λ/m, corresponding to the with harmonic of the periodic structure. The results are given of an experimental study of diffraction by a grating with a rectangular groove profile formed in a structure consisting of an As₂S₃ film and of a waveguide produced by ion exchange in glass. An investigation was made of the electrooptic interaction in a phase grating induced by the application of an electric field to an opposed-comb system of electrodes applied to a planar CdS_x Se_1–x waveguide. Three Bragg diffraction orders were observed and the halfwave voltages were 18 and 32 V for the first and second orders, respectively.