A detailed model of diffraction of plane and Gaussian beams on plane uniform phase Bragg gratings based on a Kogelnik\u27s theory of coupled waves is presented. The model describes reflecting gratings (Bragg mirrors) with arbitrary orientation in a plane-parallel plate having no material losses. It takes into account spectral width and angular divergence of laser beams. The results of modeling are compared with experimental data for Bragg mirrors in a photo-thermo-refractive glass
