Fabrication of Ag/PP terahertz hollow waveguide by vacuum evaporation method and transmission performance investigations

This work proposed a vacuum evaporation method in preparing an Ag/polypropylene (PP) terahertz (THz) hollow waveguide (HWG). Rray model and COMSOL were used to optimize the geometric structure parameters of the HWG. Accordingly, a 5 mm bore PP tube with a wall thickness of 360 μm was selected as the structural and dielectric tube, and a silver reflective layer was deposited onto the outer surface of the PP tube using vacuum evaporation process. The as-deposited Ag layer consists of small Ag particles (about 100 nm) which contribut to form a more uniform and smoother metal reflective layer than that could be prepared via the wet chemical method. Terahertz time-domain spectroscopy (THz-TDS) analysis confirms that the Ag/PP THz HWG exhibits a low-loss window centered at the frequency of 0.1 or 0.3 THz. The HWG sample shows low transmission losses of 2.26 dB/m at 0.1 THz and 1.23 dB/m at 0.3 THz, respectively. The THz waves could be stably transmitted through the as-fabricated Ag/PP waveguide at low (−78.5 °C) and high (65 °C) temperatures. This research opens a simple and environmentally friendly avenue for the fabrication of low-loss metal/dielectric THz HWG. It is helpful for promoting the applications of THz HWG in future THz imaging, sensing and 6G communication.