Switchable Plasmonic–Dielectric Resonators with Metal–Insulator Transitions

Nanophotonic resonators offer the ability to design nanoscale optical elements and engineered materials with unconventional properties. Dielectric-based resonators intrinsically support a complete multipolar resonant response with low absorption, while metallic resonators provide extreme light confinement and enhanced photon–electron interactions. Here, we construct resonators out of a prototypical metal–insulator transition material, vanadium dioxide (VO<sub>2</sub>), and demonstrate switching between dielectric and plasmonic resonances. We first characterize the temperature-dependent infrared optical constants of VO<sub>2</sub> single crystals and thin-films. We then fabricate VO<sub>2</sub> wire arrays and disk arrays. We show that wire resonators support dielectric resonances at low temperatures, a damped scattering response at intermediate temperatures, and plasmonic resonances at high temperatures. In disk resonators, however, upon heating, there is a pronounced enhancement of scattering at intermediate temperatures and a substantial narrowing of the phase transition. These findings may lead to the design of novel nanophotonic devices that incorporate thermally switchable plasmonic–dielectric behavior.