Flatland wakes based on leaky hyperbolic polaritons.

Hyperbolic polaritons facilitate nanoscale light manipulation, but strong field confinement limits their transmission across interfaces. Conversely, leaky waves can convert radiation from confined sources towards the far field. Here we combine hyperbolic polaritons and leaky wave radiation to demonstrate flatland leaky polaritonic wakes. We employ a mixed-dimensional van der Waals heterostructure consisting of a nanoscale waveguide strip on a van der Waals film. The waveguide mode, confined inside the hyperbolic light cone of the background film, enables efficient directional in-plane emission of fast phonon polaritons. The constructive interference of these leaky polaritons generates highly directional polaritonic wakes. Their spatial symmetry can be tailored through the orientation of the heterostructure with respect to the hyperbolic film dispersion. Leveraging van der Waals stacking, we also demonstrate effective acceleration and deceleration of polaritonic wakes by locally tailoring the leaky nano-waveguide dispersion through gradient thickness design. Our findings demonstrate that polaritonic wakes hold promise for integrated nanophotonic circuits.