Periodical structures, absorption spectra and dichroism induced by laser radiation in composite AgCl—Ag film

Abstract

It has been demonstrated that linearly polarized (E₀) laser beam (λ=445 nm) brings on the photoinduced transformations in AgCl—Ag composition, consisting of thin waveguide AgCl film on the glass and covered by Ag nanoparticles layer. Before the laser irradiation the sample has an absorption band related to localized plasmons in nanoparticles. Laser radiation excites plasmons and leads to waveguide TE₀-modes scattering. Periodical structure develops under modes interference with the incident wave. Its scratches are formed by Ag particles and aligned with E0 predominantly. Measured by means of diffraction structure period (291 nm) is coincident with a value calculated using TE₀-mode dispersion equation. A linear dichroism in absorption and a spectral drop (at λ≈445 nm) in the E//E₀-polarized absorption spectrum are revealed. It is shown that the structures remain on the glass substrate after AgCl removal by means of a fixing agent. The dichroism value and its dispersion are modified after the fixing.