Terahertz Thin-Film Sensing with Angle-Susceptable Metasurface

We propose and examine the idea of THz thin-film sensing using a metasurface with a narrowband plasmonic resonance sensitive to the angle of radiation incidence. A single-layer metasurface comprised of hexagon-shaped annular slots with the resonant passband near 0.8-0.9 THz is investigated numerically and experimentally by tracking the transmission under oblique illumination. It is shown that the metasurface enables detection of submicron-thick analyte layers not only via recording the THz spectrum but also in the regime of single-wavelength operation when measuring the transmittance as a function of the incidence angle.