Collective near-field coupling in infrared-phononic metasurfaces for nano-light canalization
Abstract
Polaritons, coupled excitations of photons and dipolar matter excitations, can propagate along anisotropic metasurfaces with either hyperbolic or elliptical dispersion. At the transition from hyperbolic to elliptical dispersion (corresponding to a topological transition), various intriguing phenomena are found, such as an enhancement of the photonic density of states, polariton canalization and hyperlensing. Here we investigate theoretically and experimentally the topological transition and the polaritonic coupling of deeply subwavelength elements in a uniaxial infrared-phononic metasurface, a grating of hexagonal boron nitride (hBN) nanoribbons. By hyperspectral infrared nanoimaging, we observe, for the first time, a synthetic transverse optical phonon resonance (that is, the strong collective near-field coupling of the nanoribbons) in the middle of the hBN Reststrahlen band, yielding a topological transition from hyperbolic to elliptical dispersion. We further visualize and characterize the spatial evolution of a deeply subwavelength canalization mode near the transition frequency, which is a collimated polariton that is the basis for hyperlensing and diffraction-less propagation. Our results provide fundamental insights into the role of polaritonic near-field coupling in metasurfaces for creating topological transitions and polariton canalization.
Keywords
Cite
@article{arxiv.2006.01506,
title = {Collective near-field coupling in infrared-phononic metasurfaces for nano-light canalization},
author = {Peining Li and Guangwei Hu and Irene Dolado and Mykhailo Tymchenko and Cheng-Wei Qiu and Francisco Javier Alfaro-Mozaz and Felix Casanova and Luis E. Hueso and Song Liu and James H. Edgar and Saül Vélez and Andrea Alu and Rainer Hillenbrand},
journal= {arXiv preprint arXiv:2006.01506},
year = {2021}
}