Optical microscopy of quasi-periodic structures induced upon excitation of waveguide TE and TM modes under irradiation of AgCl-Ag films by a laser beam

This paper reports on the results of analyzing the conditions under which quasi-periodic structures induced in AgCl-Ag photosensitive films by a linearly polarized Gaussian laser beam (λ=633 nm) can be clearly observed with the use of an optical microscope. It is shown that quasi-periodic structures with vectors K ∥ E (where E is the vector of polarization of the inducing beam) and periods d > λ are effectively formed upon excitation of waveguide TM₀ modes at a large angle of incidence (φ=70°) and the p polarization of the inducing beam. Exposure of the film on a 60° glass prism to a p-polarized beam incident on the sample at an angle φ=60° from the side of the glass leads to the effective formation of primary gratings with vectors K⊥E (due to the excitation of waveguide TM₀ modes) and secondary oblique gratings. The specific features of the quasi-periodic structures and the correlation between the primary and secondary gratings are revealed and analyzed.