Tunable terahertz filter composed of an array of subwavelength metallic ring apertures

We demonstrate a reconfigurable structure on a low-loss polystyrene foam substrate functioning as a tunable terahertz filter. The device consists of periodic metallic rings with a tunable lateral spacing between the outer holes on the upper layer and the inner pillars that are attached to the substrate. The device works in the transmission mode and its polarization-dependent resonance frequency can be adjusted by moving the perforated metallic membrane with respect to the pillars. The transmission characteristic of this periodic structure is studied in detail and used to optimize its configuration. It is shown that the tuning range, resonance frequency, and bandwidth of the filter can be controlled by properly scaling the geometrical parameters of the filter, i.e., the inner and outer radii of the holes, the height of the upper metallic membrane and the periodicity of the structure. This device is polarization-sensitive and can be tuned over a wide frequency range from 1.03 THz to 1.4 THz for terahertz waves polarized perpendicular to the displacement direction of the membrane.