Absorption peak wavelength and bandwidth control in MoS2-based absorbers on the basis of SPPs and LSPs excitation

Abstract

The nanometer-sized absorber that we introduced in this paper consists of a monolayer of atomically thin MoS2 on a silica substrate covered by inclined gold gratings. By selecting the period of the gold grating of the order of the incident light wavelength, both surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs) can be excited in the structure at the visible spectrum. By selecting different values of the gold ribbon’s widths, we show that the excited modes can be adjusted to SPPs, LSPs, or SPPs and LSPs together. With the excitation of SPPs, the narrowband absorption peak wavelength, and with the excitation of LSPs, the FWHM of the absorption peak can be adjusted by the ribbon’s geometry parameters. In the case of simultaneous excitation of SPPs and LSPs, by increasing the ribbons’ inclination, the LSP peaks will redshift, while the SPP peaks blueshift, which leads to wider absorption peaks. The effect of increasing the ribbons’ height is opposite to that of the ribbons’ inclination, which is accompanied by the SPP peak red shift and LSP peak blue shift. This way, the more the height of the ribbons, the less the absorption peak bandwidth is. This paper’s results are a promising guide for designing plasmonic absorbers with desired bandwidths and peak wavelengths, which are widely demanded in designing photovoltaics and photonic sensors.