Terahertz narrow-band filter based on 3D-printed periodic waveguides

Abstract

Terahertz (THz) devices, especially waveguide-type functional devices related to transmission and control, are severely scarce due to the lack of effective design and fabrication methods. Here, we experimentally demonstrate a waveguide type of THz narrow-band filter based on 3D-printed technology, which is realized by a cylindrical hollow metal structure with corrugated tube walls. The semi-cylindrical periodic corrugations are 3D printed on a photosensitive resin substrate material, followed by sputtering a layer of gold film on its surface to endow the structure with THz filtering functions. A hollow cylindrical corrugated waveguide is obtained by assembling two identical semi-circular corrugations together. The periodic structure with Bragg resonances can produce a frequency stop band, in which the propagation of THz waves is significantly suppressed. We print a wider section of corrugations in the middle of the waveguide, which destroys the perfect periodicity of the structure and forms a defect. Due to the local resonance caused by the defect, we observe an additional narrow-band transmission peak within the former stop band, which is a good candidate for THz filtering. The filtering bandwidth and extinction ratio are 1.8 GHz and 28 dB, respectively, and the Q-factor reaches 234. The proposed 3D-printed THz filter has the advantages of the simple structure, excellent performance, and easy integration, which can improve the existing THz systems in various applications.