Transmission and Confocal Imaging Characteristics of Bendable ABS/Ag-Coated Hollow Waveguide at Low THz Band

A bendable Ag-coated hollow waveguide (HWG) based on the acrylonitrile-butadiene-styrene (ABS) tube is fabricated for low-loss transmission and imaging of low-frequency terahertz (THz) waves. ABS plastic tubing is selected since it allows growing a smooth silver (Ag) reflective film with good adhesion to the inner wall and contributes to constructing a bendable THz HWG structure. The low-loss transmission window of the ABS/Ag-coated HWG is at 0.2-1.0 THz. The attenuation characteristics of the as-prepared waveguide samples with different bore sizes (2.3, 3.2, and 4.2 mm) at 100 and 300 GHz are investigated. The 3.2-mm-bore THz waveguide exhibits good bendability and transmission performance. Its measured straight transmission loss is 1.02 dB/m at 300 GHz, and the bending loss reaches 1.56 dB/m at 150° (the curvature radius is 10 cm). Moreover, a far-field confocal waveguide-based THz imaging system is established based on the ABS/Ag-coated HWG. High-quality imaging with a super-resolution of 1.12 mm was achieved using the 3.2-mm-bore waveguide samples at 100 GHz.