Active gratings tuned by thermoplasmonics-induced phase transition in vanadium dioxide thin films

We propose and investigate an active grating of gold metallic structure on vanadium dioxide (VO₂) thin film illuminated by an intense light. Nonuniform phase transition in VO₂ film is expected due to the thermoplasmonics effect where the plasmonic-induced light absorption features an enhanced local heat generation at nanometer-scale. The spatial profiles of the electric field, the heat generation, and the temperature distribution, as well as the temperature-dependent dielectric parameters in VO₂ film, are solved numerically in a self-consistent manner. Our results show that the evolution of the metallic and semiconducting phases of VO₂ changes the effective dielectric environment of the grating and modifies its optical response in a controlled way. The interplay of the thermoplasmonics effect and the phase transition processes can thus provide another degree of freedom in designing optical modulators or switches which are remotely tunable via incident light.