Low loss and single mode metal dielectric hybrid-clad waveguides for Terahertz radiation

Abstract

Several waveguide solutions based on technologies from both electronics and photonics have been proposed for guiding Terahertz (THz) radiation. Hollow-core dielectric waveguides are one of the best options for guiding THz radiation since the material absorption is almost zero in the air-core. However, these waveguides are usually multimode and have dimensions in the order of a few millimeters. Here we propose a hollow-core waveguide with sub-wavelength scale metallic wires in the cladding for THz guidance. The theoretical studies show that such a hybrid cladding reflects the transverse magnetic (TM) waves and transmits the transverse electric (TE) waves, leading to a waveguide structure that only confines TM modes. The numerical simulations show a pure single mode, single polarization operation window from 0.22 THz to 0.34 THz and 14.8 dB/m propagation loss at 0.29 THz. Compared to a metallic waveguide with similar dimension, the proposed waveguide more than doubles the single mode operation bandwidth with comparable losses. We discuss the effect of optical and structural parameters of the hybrid cladding on the single mode operating window and propagation losses, and suggest methods of fabrication of the waveguide. The design principle of the proposed waveguide can be extended to the mid-inferred spectrum.