Hybridized Hyperbolic Surface Phonon Polaritons at α-MoO₃ and Polar Dielectric Interfaces

Surface phonon polaritons (SPhPs) in polar dielectrics offer new opportunities for infrared nanophotonics. However, bulk SPhPs inherently propagate isotropically with limited photon confinement, and how to collectively realize ultralarge in-plane hyperbolicity, unidirectional propagation remains elusive. Here, we report an approach solve the aforementioned issues of one go by constructing a heterostructural interface between biaxial van der Waals material (e.g., α-MoO3) dielectric SiC, AlN, GaN). Because anisotropy-oriented mode couplings, hybridized large confinement factor (>100) show hyperbolicity that has been switched orthogonal direction as compared natural α-MoO3. More interestingly, this proof concept allows steerable polariton excitation suspending α-MoO3 on patterned SiC air cavities. Our finding exemplifies generalizable framework manipulate flow nanolight many other hybrid systems consisting anisotropic materials dielectrics.