A Photogenerated Silicon Plasma Waveguide Switch and Variable Attenuator for Millimeter-Wave Applications

This article reports the design, fabrication, and measurement of a millimeter-wave (mm-wave) solid-state
$\pi $
-match waveguide switch using bulk silicon micromachining. A photogenerated plasma within a silicon post is utilized as the switching element within the waveguide channel. Not only does this isolate the switch bias network from the RF signal path but also allows for tuning of the OFF-state isolation with increasing optical power for application as a variable attenuator. A measured OFF-state isolation greater than 25 dB up to 40 GHz is reported, with a measured extracted ON-state insertion loss of 0.52 dB at 35 GHz, and less than 0.88 dB across the entire band from 30 to 40 GHz. The proposed switch illustrates the significant potential for photogenerated silicon plasma switching of high-performance bulk micromachined mm-wave waveguides.