Multilayer surface waveguide cavity resonance based on coupled surface plasmon-phonon polaritons

Surface phonon polaritons have emerged as promising candidates for applications in the long-wave infrared spectrum. Recent advancements in resonant cavity design, based on coupled surface plasmon-phonon polaritons, have demonstrated near-perfect and controllable absorptions, making them a potential candidate for constructing building blocks in long-wave infrared metasurfaces. We have utilized phase-changing materials for active metasurfaces, particularly vanadium dioxide, which undergoes an insulator-to-metal transition near room temperature. However, vanadium dioxide exhibits a higher refractive index at long-wave infrared frequencies, leading to challenges such as higher optical power losses. We address these challenges by constructing a multilayer surface waveguide that can effectively transform into a cavity. The multilayer surface waveguide minimizes losses and accommodates larger device sizes for practical fabrication. We model a multilayer surface waveguide to investigate the dispersion of coupled surface plasmon-phonon polaritons and to identify the Fabry-Perot resonance condition that arises when the cavity is formed. Our study includes various types of polar dielectrics, namely SiC, Al2O3, and GaAs. The multilayer consists of passive SiO2 and active VO2 layers.