Submillimeter-Wave 90 $^{\circ}$ Polarization Twists for Integrated Waveguide Circuits

We present a novel full-waveguide-band 90° polarization twist implemented in full-height rectangular waveguide suitable for use in submillimeter-wave and terahertz-integrated waveguide circuits. Combined benefits of simplified fabrication, suitability for silicon micromachining, suitability for integration with other components into integrated waveguide circuits without interconnecting flanges, and alleviation of waveguide associated losses and mismatches, make this component well-suited for submillimeter-wave applications. A polarization twist fabricated for WR-3 waveguide with UG-387/UM flanges was tested to confirm insertion loss better than 0.5 dB and return loss better than 20 dB from 220 to 320 GHz. We also fabricated and tested a polarization twist scaled to the 500-700 GHz band. By using only a single constant-depth channel in addition to the E-plane and H-plane split waveguide channels, this component is well optimized for fabrication with silicon micromachining, making it scalable to at least 5 THz.