Manipulating birefringence in AgCl thin film loaded by silver nanoparticles under normal and oblique incident angles

Abstract

We have induced anisotropy in AgCl thin film, which is loaded by silver nanoparticles, by irradiating a single low power laser beam at wavelength 532 nm. The induced anisotropy in Ag–AgCl thin film is due to the formation of gratings in the direction of light polarization for both normal and oblique angles of laser incidence. In Ag–AgCl thin film, which was irradiated by oblique laser beam, complex grating with different line-spaces is formed. It turns out that the line-spaces of the grating depend on the incident angle. Therefore, by changing the incident angle of the laser beam, the morphology and optical properties of anisotropic nanostructures formed on Ag–AgCl thin film can be manipulated. Linear birefringence and linear dichroism are measured in these nanostructures by probe beams at different wavelengths in the visible region. Our results show that the sample which is irradiated normally has the largest linear birefringence and linear dichroism compared to the oblique incident samples. In the normal incident sample, the maximum value of linear birefringence is seen at wavelength 632.8 nm (Δn = 0.35), while the largest absolute value of linear dichroism is observed at wavelength 532 nm, which is the same wavelength as the incident laser beam.