POLARIZATION TRANSFORMATION OF ELECTROMAGNETIC RADIATION AT EXCITATION OF SURFACE PLASMON-POLARITONS ON A METALLIC GRATING

Abstract

The results of experimental studies of plasmon-stimulated transformation (conversion) of radiation polarization by Au gratings with different ratio between lattice period and excitation wavelength (including the first time investigated high-frequency gratings, for which the ratio of wavelength to period is close to 2), as well as with different modulation depth, are presented. Gratings for research are made by means of interference lithography using chalcogenide photoresists. The polarization conversion effect was studied by measuring the angular dependences (on the angle of incidence and azimuthal angle) of the specular reflection of linearly polarized monochromatic He-Ne laser radiation. It was found that for low-frequency gratings with a period more than wavelength and for the gratings with an intermediate frequency (grating period is a little less than wavelength), the maximum conversion efficiency for p-polarized radiation into s-polarized is reached at azimuth ~45° and is determined by the modulation depth. However, for high-frequency lattices on which surface plasmon-polaritons are excited at high incidence angles and azimuthal angles significantly less than 45°, the intensity of the resulting s-component is an order of magnitude less than for lower-frequency lattices. Thus, the efficiency of polarization conversion stimulated by the excitation of surface plasmons is determined not only by the lattice depth of modulation h/d, but also by the ratio of the exciting light wavelength to the lattice period λ/d.