Tunable polaritonic metasurface absorbers in mid-IR based on hexagonal boron nitride and vanadium dioxide layers

Here, a metasurface absorber with switchable spectral response is proposed and discussed. The device is constructed by combining a phase change material (vanadium dioxide, VO ₂ ) and a naturally hyperbolic materials (hexagonal boron nitride, hBN), utilizing surface plasmon polaritons (SPPs) and surface phonon polaritons (SPhPs), respectively, at different thermal conditions in the same system. Specifically, we take advantage of the excitation of SPhP in hBN below the VO ₂ critical temperature (T < T _c ) and SPP from VO ₂ layers at higher temperatures (T > T _c ), to switch between narrow-band near-perfect absorption at ∼7.2 μm to broadband absorption at 8-12 μm. It is shown that SPPs and SPhPs can be excited, respectively, by controlling the temperature, offering new opportunities in designing tunable artificial materials and devices for promising nanophotonics applications.