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 (VO2), and demonstrate
switching between dielectric and plasmonic resonances. We first characterize
the temperature-dependent infrared optical constants of VO2 single crystals and thin-films. We then fabricate VO2 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.