Abstract
Relief periodic structures (RPS) induced in photosensitive thin polycrystalline AgI films at normal incidence by laser beams with wavelengths of 1-441.6 nm and 632.8 nm due to excitation of Tem and TM waveguide modes by scattered light were studied. The period in the RPS is related to the mode distribution constant by the phase-matching condition, which determines the RP growth due to positive feedback. It is shown that the mode-locked relief RPS has virtually no effect on θ and the dependence of α on the film thickness and is well described by the dispersion relation of a planer waveguide. In The AgI-ZnS thin film system, TM RPS were simultaneously obtained on modes of different orders, the distribution of diffraction efficiencies of the RPS is consistent with the distribution of surface losses for the corresponding modes. The possibility of using the RPS to determine H and the refractive index of a non-photosensitive waveguide layer (ZnS) is discussed. The formation of the PS under the action of a 2-632.8 nm beam, which corresponds to the transparency region of AgI, is explained by nonlinear two-stage absorption associated with the centers of the latent image.