Terahertz filters based on subwavelength polymer waveguide

Manipulation of terahertz (THz) waves is one of the key processes in compact and robust THz systems, where functional waveguide devices are in huge demand. To filter THz beams at expected frequencies, we raise a proposal of polarization insensitive THz dielectric grating with circular symmetry at subwavelength dimension. Large-sized cylinders are periodically introduced on a low-loss subwavelength THz waveguide, resulting into a stopband in transmission profile - a resonate response of guided modes. Using numerical models, impacts of structural parameters on the grating filtering characteristics and the tunability are investigated. Simulation results show that the full-width half-maximum and extinction ratio values of the proposed grating can be 20 GHz and 0.55 at around 0.3 THz, respectively. We also discuss the fabrication tolerance and material selection of the THz grating. Our work illustrates a promising grating structure enabling filtering the THz beam in sensing, imaging and wireless communication applications. In addition, thanks to the circular symmetry, the proposed filter is polarization-independent of THz waves, which means the filters here are more flexible in a practical view.