Optical activity of VO2 based nanophotonics

Being a Mott type oxide, at a temperature of 68°C and ambient pressure, stoichiometric VO₂ undergoes a first order metal-insulator transition, which is accompanied by a structural transition from a high-temperature rutile phase to a low-temperature monoclinic phase. The latter result causes an abrupt change in the resistivity over several orders of magnitude induced by the band gap opening. From optical point of view, this metal-insulator transition is accompanied by a significant and reversible variation of the refractive index under a thermal stimuli. Hence, VO₂ based coatings have been attracting considerable interest for fundamental reasons, and certainly for technological applications in the solar energy sector and ultrafast linear and nonlinear photonics. In this contribution, the photonic multi-functionality of nano-structured VO₂ based coatings are presented. This includes applications such as (i) smart window for solar heat modulation, (ii) active coating for heat management in satellites, (iii) ultrafast opto-electronic gating, (iv) ultrafast optical limiting and (iv) femtosecond tunable nano-plasmonics.