Fabrication method of small-diameter hollow waveguides for terahertz waves

To develop a thin and flexible hollow waveguide for terahertz (THz) waves that can be applied to endoscopic applications, a new (to our knowledge) fabrication method is proposed in which thin polymer tubing is first drawn and then a silver layer is formed on the outside of the tubing. By using this method, a thick dielectric layer, which was difficult to form by liquid-phase deposition, is easily obtained with high accuracy in the thickness. A transmission loss at 1.5 THz measured by a Fourier transform IR spectrometer was 3.0 dB for a 50 cm long, 1 mm inner-diameter waveguide. It is shown that the transmission losses are not affected by the bending of the waveguide when the bending radius is larger than around 10 cm.