Polarization Transformation of Electromagnetic Radiation Upon Excitation of Surface Plasmon-Polaritons on a Metallic Grating

Abstract

Plasmon-stimulated transformation (conversion) of radiation polarization by Au gratings with different ratios of excitation wavelength to lattice period (including high-frequency lattices with a wavelength to period ratio of close to 2 that are studied for the first time) and with different modulation depths are experimentally studied. Gratings for research are made by interference lithography using chalcogenide photoresists. Polarization conversion is studied by measuring angular dependences (on the incident and azimuthal angles) of the specular reflection of linearly polarized monochromatic He–Ne laser radiation. The maximum conversion efficiency for p-polarized into s-polarized radiation for low-frequency lattices with a period greater than the wavelength and lattices with an intermediate frequency (period slightly less than the wavelength) is found at azimuth ~45o and is determined by the modulation depth. However, the intensity of the resulting s-component is an order of magnitude less for high-frequency lattices on which surface plasmon-polaritons are excited at high incident angles and azimuthal angles significantly less than 45o than for lower-frequency lattices. Thus, the efficiency of polarization conversion stimulated by excitation of surface plasmons is determined not only by lattice modulation depth h/d but also by the ratio of the exciting light wavelength to the lattice period λ/d.