A terahertz band-pass resonator based on enhanced reflectivity using spoof surface plasmons

Abstract

We demonstrate a band-pass resonator in the terahertz (THz) range, based on a frequency-selective designer reflector. The resonator consists of a parallel-plate waveguide, a designed groove pattern cut into the output facet of each plate, and a reflecting mirror. The patterned facet supports a spoof surface plasmon mode, which modifies the reflectivity at the waveguide output facet by interacting with the waveguide mode. By tuning the geometrical parameters of the groove pattern, the reflectivity at the patterned output facet can be increased up to ∼100% for a selected frequency. Broadband THz waves are quasi-optically coupled into this resonator and reflected multiple times from the patterned facet. This leads to a narrowing of the spectrum at the selected frequency. The Q value of the resonator increases as the number of reflections on the patterned facet increases, reaching ∼25 when the THz wave has experienced 12 reflections.

Focus on terahertz plasmonics

“…J Liu et al fabricated a THz bandpass resonator by use of a parallel-plate waveguide with corrugated plates on one output facet and a mirror on the other end. After geometric optimization they observed 100% reflectivity at the patterned output facet for narrow frequency range, thus being able to devise a high Q THz subwavelength resonator [4]. Schaafsma et al used a single plasmonic bowtie antenna consisting of two n-doped silicon monomers with triangular shape and facing apexes for resonant extinction of THz radiation at the output facet of a conically tapered waveguide [5].…”