WR-3 Waveguide Bandpass Filters Fabricated Using High Precision CNC Machining and SU-8 Photoresist Technology

This paper presents two WR-3 band (220-325 GHz) filters, one fabricated in metal using high precision computer numerically controlled milling and the other made with metallized SU-8 photoresist technology. Both are based on three coupled resonators, and are designed for a 287.3-295.9-GHz passband, and a 30-dB rejection between 317.7 and 325.9 GHz. The first filter is an extracted pole filter coupled by irises, and is precision milled using the split-block approach. The second filter is composed of three silver-coated SU-8 layers, each 432 μm thick. The filter structures are specially chosen to take advantage of the fabrication processes. When fabrication tolerances are accounted for, very good agreement between measurements and simulations are obtained, with median passband insertion losses of 0.41 and 0.45 dB for the metal and SU-8 devices, respectively. These two filters are potential replacements of frequency selective surface filters used in heterodyne radiometers for unwanted sideband rejection

Detection of 2.2-3.5 Terahertz Radiation Using a Quasi-Optically Mounted Planar Schottky Diode

Practical supra-terahertz (1–5 THz) heterodyne radiometry systems require compact local oscillator and mixer components, which are suitable for robust waveguide integration. We demonstrate detection of radiation emitted by quantum cascade lasers at frequencies between 2.2 and 3.5 THz using room-temperature quasi-optically mounted planar Schottky diodes. These diodes are more readily integrated into waveguides than point-contact diodes, do not require the cryogenic environment of hot-electron bolometers and offer potentially better noise performance than superlattice devices