Au nanowire-VO2 spacer-Au film based optical switches

Abstract

We present a novel optical switch that consists of a 1D array of plasmonic (Au) nanowires present on a vanadium dioxide ( VO 2 ) 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 VO 2 spacer layer, i.e., upon phase transition of VO 2 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 VO 2 layer results in a change in the reflectance signal from the Au nanowire- VO 2 spacer-Au film nanostructure. The differential reflectance signal, i.e., difference in the reflection spectra from this nanostructure when the VO 2 spacer layer is present in its metallic and the semiconductor states, was calculated using RCWA simulations and employed as a measure of switchability. 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 VO 2 film spacer occurs at femto-second time scales. These optical switches can be fabricated using currently available nanofabrication capabilities.