Submillimetre rectangular waveguides based on SU-8 photoresist micromachining technology

Rectangular waveguides are fundamental structures for the transmission of signals at millimetre and submillimetre wavelengths. This paper describes the design and measured results for two rectangular waveguides based on layered SU-8 photoresist micromachining technology, with double-layer fabrication techniques to minimise the air gaps between layers. A brief description of the SU-8 photoresist micromachining procedure is given in the paper. One waveguide is demonstrated for the WR-3 band from 220 GHz to 325 GHz the other is for the WR-6 band 120 GHz to 170 GHz both are made of layered SU-8 with a 3 piece construction. Both waveguides have novel bends in order to connect to the measurement apparatus. The measured performance is presented and compared to conventional machined metal waveguide structures. The measured insertion loss for the SU-8 waveguides in both bands is better than 0.03 dB/mm.