Non‐Hermitian metasurface with non‐trivial topology
Frank Yang, Ciril S. Prasad, Weijian Li, Rosemary Lach, Henry O. Everitt, Gururaj V. Naik
Abstract
Abstract The synergy between topology and non‐Hermiticity in photonics holds immense potential for next‐generation optical devices that are robust against defects. However, most demonstrations of non‐Hermitian and topological photonics have been limited to super‐wavelength scales due to increased radiative losses at the deep‐subwavelength scale. By carefully designing radiative losses at the nanoscale, we demonstrate a non‐Hermitian plasmonic–dielectric metasurface in the visible with non‐trivial topology. The metasurface is based on a fourth order passive parity‐time symmetric system. The designed device exhibits an exceptional concentric ring in its momentum space and is described by a Hamiltonian with a non‐Hermitian topological invariant of V = −1. Fabricated devices are characterized using Fourier‐space imaging for single‐shot k ‐space measurements. Our results demonstrate a way to combine topology and non‐Hermitian nanophotonics for designing robust devices with novel functionalities.