Mid-infrared Plasmonic Resonances in 2D VO2 Nanosquare Arrays

Plasmon resonances on 2D nanosquare arrays and their temperature-dependent modulations are demonstrated using the insulator-to-metal transition (IMT) of VO2. A comparison between observed experimental trends and electromagnetic simulations reveals that the plasmon coupling is effective in the periodic 2D alignment of metallic VO2 nanosquares and results in a collective plasmon excitation. This plasmon excitation affects the optical responses of VO2 nanosquares in the mid-infrared (IR) range through reduction of plasmon damping in relation to the specifi c band structure of VO2. This preliminary understanding is important for the elucidation of temperature-dependent plasmon resonances. The IMT of VO2 produces temperature-dependent plasmon resonances with respect to spectral features. The electrodynamic simulations reveal that these phenomena are based on plasmon coupling in the nanosquare array when each nanosquare acts as a single metallic domain. The hysteretic plasmon resonances are derived from resonant coupling between metallic VO2 nanosquares via the IMT nature of VO2, which results in temperature-dependent changes in collective plasmon excitations in the nanosquare array.