Periodical Elements as Low-Cost Building Blocks for Tunable Terahertz Filters

Periodical elements made by stacking thin layers of the cyclo-olefin polymer Zeonor, separated by spacers made of bi-adhesive tape, are used as building blocks for realizing tunable terahertz (THz) filters. The basic block is a Bragg reflector whose bandgap can be controlled by changing the geometrical features of the periodical elements. By combining two of these Bragg building blocks, separated by a void defect cavity, a tunable bandpass filter is obtained. The thickness of the defect cavity is mechanically tuned by means of a translation stage. The resulting filter are mechanically stable and they show both high transmittance and narrow linewidths, owing to the selected THz low-loss polymer.