Design and Characterization of <i>W</i>-Band Silicon Micromachined High-Power and High-Speed Photoconductive Evanescent-Mode Waveguide Single and Double Throw Switches
Eric T. Der, Thomas R. Jones, Alden Fisher, Kambiz Moez, Douglas W. Barlage, Dimitrios Peroulis
Abstract
This article details the principle of operation, design process, and characterization of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula> -band silicon micromachined evanescent-mode (EVA) waveguide switches. This work includes a detailed analysis of the ON-state response of EVA waveguide switches as well as the design of transitions to standard waveguide connector feeds. The first ever switching speed and power handling characterization of silicon micromachined EVA waveguide switches is also presented. Photogenerated plasma in silicon posts placed inside an EVA channel results in large impedance mismatch, allowing very high isolation to be achieved in the switch’s OFF-state with low optical power. In the ON-state, the unexcited silicon posts behave as shunt capacitors, allowing signal propagation through the switch in the form of a coupled resonator bandpass filter response. The design of both two-pole and three-pole filter responses in single pole single throw (SPST) and single pole double throw (SPDT) switch configurations is detailed in this article. The fabricated two-pole SPST switch achieves a 30-dB isolation with just 178 mW of optical excitation. For the three-pole SPST switch, only 111 mW is required. The extracted insertion loss (IL) of the two-pole and three-pole switching elements in SPDT configurations is just 0.16 and 0.32 dB, respectively. Furthermore, experiments presented in this article show that < 4- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> switching speeds are realized by this technology, and that the switching elements are able to handle at least +32 dBm of continuous power at 85 GHz.