A W-Band Photoconductive Evanescent-Mode Waveguide Switch

This paper presents the design, fabrication, and measurement of a W-band photoconductive evanescent-mode waveguide shunt switch using bulk silicon micromachining. The switching element is formed by a photogenerated plasma within a silicon post located inside an evanescent-mode region of a waveguide channel. Two silicon posts are coupled within the evanescent-mode region for an inline bandpass filter architecture, enabling low insertion loss in the switches ON-state, and large signal isolation versus applied optical power in the OFF-state. Two prototypes are fabricated and measured, the first demonstrating low ON-state insertion loss of 0.47 dB at 82.3 GHz, and the second demonstrating OFF-state isolation greater than 48 dB up to 100 GHz. The proposed design has significant potential for integrated high power millimeter-wave switching for wireless backhaul in future 5G and 6G communication networks.