Narrow Linewidth Terahertz Filter Based on Gold-Coated Polymer Plates With Corrugations

Terahertz (THz) devices, especially for narrowband filters, have been widely investigated over the past decades, but mostly based on semiconductor materials or metamaterials. Here, we experimentally and numerically demonstrate a waveguide-type narrowband THz filter, which is realized by two parallel plates with corrugations. The corrugated plates are fabricated by sputtering a layer of gold after laser ablation of polymer sheets. The laser periodically etches the groove and produces a wide groove in the middle, which destroys the periodicity of the structure and forms a defect. The periodicity provides a forbidden band, in which THz waves cannot propagate, and the defect leads to an additional transmission in the forbidden band. This additional transmission occurs in the middle of the gap and has a very narrow linewidth, which is a good candidate for THz filtering. The achieved linewidth and the extinction ratio are about 1.5 GHz and 29 dB, respectively, limited by our experimental system, which are further optimized in numerical simulations. The proposed fabrication method is very efficient in THz waveguide devices, which can be easily integrated in applicable THz systems.