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

Automated summary

In this study, the issues of limited photon confinement, in-plane hyperbolicity, and unidirectional propagation of bulk SPhPs were collectively addressed by constructing a heterostructural interface between biaxial van der Waals material and bulk polar dielectric. The hybridized SPhPs showed in-plane hyperbolicity with a large confinement factor (>100), and steerable and unidirectional polariton excitation was achieved. This approach provides a generalizable framework for manipulating nanolight flow in hybrid systems consisting of anisotropic materials and polar dielectrics.