A novel photlithographic technique has been developed for the fabrication of fundamental mode metal pipe waveguide foroperation at frequencies between 300GHz and Ã¢â‚¬â€2THz. The guides are formed on a semiconductor substrate and henceactive devices such as Schottky or Resonant Tunnelling Diodes ( RTD ) may be incorporated within them.
A. S. Treen, A. S. Treen,
"Terahertz metal pipe waveguides", Proc. SPIE 2104, 18th International Conference on Infrared and Millimeter Waves, 21046N (30 August 1993); doi: 10.1117/12.2298671; https://doi.org/10.1117/12.2298671