Abstract. We present results of experiments to determine the dispersion of the plasmon modes associated with Au nanowire gratings with a fixed spatial frequency (3370 mm–1) and different slits between the nanowires fabricated using an interference (interferometric) lithography technique. Optical properties of fabricated plasmonic structures were studied using measurements of spectral and angular dependence of P- and S-polarized extinction in the wavelength range 0.4…1.1 μm, angles of incidence 10…70 degrees in conical mounting (at variable azimuth angle within the range φ = 0…90 degrees). It has been shown that in the grating with the average slit between the nanowires equal to half of the grating period at φ = 0 only local plasmons (LP) are excited by P-polarized light. When the azimuth angle changes from 0 to 90°, the intensity of the excited LP is smoothly “transferred” from P- to S-polarized excitation, and at φ ~ 30…45 degrees the intensities of the LP bands in both polarizations are approximately equal. However, in the sample with narrow slits between the nanowires (40 nm) we observe the mixed mode with excitation both surface plasmon-polariton (SPP) and LP in the P-polarization at φ = 0. With φ rising, the intensity of the mixed mode in P-polarization decreases and simultaneously the LP mode intensity in S-polarization increases.

Keywords: plasmonic gratings, surface plasmon resonance, interference lithography, azimuthal rotation.

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