Au nanowire-VO2 spacer-Au film based optical switches

We present a novel optical switch that consists of a 1D array of plasmonic (Au) nanowires present on a vanadium dioxide (VO2) thin film layer, which is further present on top of an underlying plasmonic (Au) film. The optical switching action in this nanostructure arises from the semiconductor-to-metal transition of the VO2 spacer layer, i.e., upon phase transition of VO2 from its semiconductor state to its metallic state, which can be induced by the application of heat, infrared light, or voltage. The phase transition of the VO2 layer results in a change in the reflectance signal from the Au nanowire-VO2 spacer-Au film nanostructure. The differential reflectance signal, i.e., difference in the reflection spectra from this nanostructure when the VO2 spacer layer is present in its metallic and the semiconductor states, was calculated using simulations and employed as a measure of switchabilaty. We demonstrate that switchability, as well as the wavelength at which the maximum differential reflectance is observed (i.e., the optimal switching wavelength), can be tuned over a wide spectral regime by changing the structural parameters of these optical switches. Ultrafast switching can be achieved using these optical switches, as the phase transition in the VO2 film spacer occurs at femto-second time scales. These optical switches can be fabricated using currently available nanofabrication capabilities. (C) 2018 Optical Society of America.