Abrupt Insertion Loss Drop by RF-Triggering of the Phase Transition in ${\rm VO}_{2}$ CPW Switches

We demonstrate an abrupt drop in insertion loss (up to 21 dB) at a critical RF (10 GHz) power in 2-port series co-planar waveguides incorporating vanadium dioxide thin films. We rigorously determine the critical delivered power for switching by calculating the waveguide reflection coefficients from a lumped element model. Through analysis of the critical RF power, we find definitively that the drop is caused by RF triggering of the vanadium dioxide metal-insulator phase transition in the absence of DC bias. The sharp insertion loss drop may have use in broadband receiver protectors, RF switching, and tunable coupling applications.