Porous Silicon Waveguides for Integrated Sub-THz Systems

This letter presents the first experimental demonstration of a new type of silicon-integrated sub-terahertz (THz) waveguide, based on porous silicon (PS). The waveguide (WG) is realized on an ultralow-resistivity (ULR) silicon substrate using a single-step electrochemical anodization that codefines material and geometry, eliminating deep reactive-ion etching (DRIE) and wafer bonding. A coplanar-waveguide-to-PS-WG transition enables direct on-wafer characterization. The fabricated PS WG is targeted for D-band operation and exhibits a measured attenuation loss of 0.7 dB/mm at 140 GHz, in excellent agreement with full-wave simulations. This confirms the validity of the codesign approach. Combining low loss, simplified fabrication, and inherent material tunability, the proposed PS WG offers a promising route toward highly integrated sub-terahertz passive components and enables future gas and biosensing applications.