Long-Range Polariton Canalization in a Graphene-Nanoribbon-Covered MgTeMoO6 Metasurface.

van der Waals (vdW) quaternary oxide structures, such as MgTeMoO6 slabs and nanoribbons, have recently emerged as promising platforms for demonstrating polariton propagation with hyperbolic dispersion and canalization. This expands the catalog of exceptional optical and electronic vdW materials. By leveraging topological transitions, various vdW heterostructures can induce extraordinary in-plane canalized polaritons. Yet, achieving long-range canalized polariton propagation has remained a significant challenge. In this study, we introduce a novel approach by covering the ridge tops of an MgTeMoO6 metasurface with graphene ribbons. This configuration significantly extends the propagation length of canalized polaritons to an unprecedented 7.95 μm, which is more than 20 times the propagation distance observed in a bare MgTeMoO6 metasurface. This enhancement is achieved through the coherent coupling of graphene plasmon polaritons and MgTeMoO6 phonon polaritons, forming a guided phase-locked mode that minimizes energy losses. Notably, the resulting canalized polaritons exhibit exceptionally long lifetimes of around 86 picoseconds, surpassing previously reported vdW platforms. Simulations using an antenna-launched setup confirm the experimental feasibility of our design. These findings open new avenues for applying polaritonic vdW platforms in nanophotonics, super-resolution imaging, and diffraction-less hyperlensing in the mid-infrared regime.