Yang, FrankPrasad, Ciril S.Li, WeijianLach, RosemaryEveritt, Henry O.Naik, Gururaj V.2022-04-282022-04-282022Yang, Frank, Prasad, Ciril S., Li, Weijian, et al.. "Non-Hermitian metasurface with non-trivial topology." <i>Nanophotonics,</i> 11, no. 6 (2022) De Gruyter: 1159-1165. https://doi.org/10.1515/nanoph-2021-0731.https://hdl.handle.net/1911/112158The 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 Z 3 ${\mathbb{Z}}_{3}$ 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.engThis work is licensed under the Creative Commons Attribution 4.0 International License.Journal article10-1515_nanoph-2021-0731https://doi.org/10.1515/nanoph-2021-0731