Thermally tunable mid-infrared nanocavity resonance of coupled surface plasmon-phonon polaritons.

Phase-change materials (PCMs) are essential for achieving tunability of metasurfaces. However, they frequently face limitations in the long-wave infrared range because of their lossy behavior. Here, we experimentally demonstrate a thermally tunable mid-infrared nanocavity resonance from coupled surface plasmon-phonon polaritons that are supported within a trilayer structure of metal-PCM layer-polar dielectric (Au-VO-SiC). The top metal structures configure the Fabry-Perot cavity resonance near 840 cm (11.9 m), which is sensitively tunable and reversible with small changes in the VO refractive index Δ near below its insulator-to-metal phase transition temperature where the loss is small. The maximum resonance shift of 7.7 cm is induced by a small Δ = 0.3 over a temperature change of 3°C. The tuning figure of merit is comparable to the current standard in photonic modulator applications.