Van der Waals metasurfaces molding topological polaritons

Polaritons, formed through the strong coupling of photons with excitations such as phonons or excitons, offer powerful tools for manipulating light at subwavelength scales. Van der Waals materials, like hexagonal boron nitride (hBN) and other transition metal dichalcogenides (TMDs), present unique opportunities for controlling polaritonic modes due to their atomically thin structures and tunable optical properties. Specifically, hyperbolic polaritons in hBN enable extreme light confinement and canalization in the mid-infrared spectral range, while exciton-polaritons in TMDs exhibit strong nonlinear responses in the visible and near-infrared domains. Integrating van der Waals materials with metasurface—a tailored array of subwavelength scatterers—enables the creation of topologically protected polaritonic states, allowing unidirectional, scattering-resistant propagation. This review provides a brief review of the rapidly advancing field of topological polaritonics in van der Waals metasurfaces, covering not only topological polaritonic insulators but also hyperbolic polaritons exhibiting topological transition in their dispersion contour.