Anapole-assisted absorption engineering in arrays of coupled amorphous gallium phosphide nanodisks

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Title: Anapole-assisted absorption engineering in arrays of coupled amorphous gallium phosphide nanodisks
Authors: Hüttenhofer, L
Tittl, A
Kühner, L
Cortés, E
Maier, SA
Item Type: Journal Article
Abstract: Broadband solar light harvesting plays a crucial role for efficient energy conversion. Anapole excitations and associated absorption engineering in dielectric nanoresonators are a focus of nanophotonic research due to the intricate combination of nonradiating modes and strong electromagnetic field confinement in the underlying material. The arising high field strengths are used for enhanced second-harmonic generation and photocatalysis, where devices require large areas with closely spaced nanoresonators for sizable photonic yields. However, most anapole studies have so far been carried out at the single-particle level, neglecting the influence of anapole–anapole interactions. Here, we present a systematic study of coupling mechanisms in rectangular arrays of amorphous GaP nanodisks that support anapole excitations at 600 nm, which is within the lossy spectral regime of the material. Our experimental findings show that maximum visible light extinction by the array and maximum absorption in the GaP are not achieved by the densest packing of resonators. Counterintuitively, increasing the array periodicities such that collective effects spectrally overlap with the anapole excitation of a single particle leads to an absorption enhancement of up to 300% compared to a single disk. An analysis of coupling in one- and two-dimensional arrays with polarization-dependent measurements and numerical simulations allows us to discriminate between coupling interactions parallel and perpendicular to the polarization axis and evaluate their strengths. Utilizing a multipolar decomposition of excitations in single nanodisks embedded in one-dimensional arrays, we can attribute the coupling to enhanced electric and toroidal dipoles under variation of the interparticle spacing. Our results provide a fundamental understanding of tailored light absorption in coupled anapole resonators and reveal important design guidelines for advanced metasurface approaches in a wide range of energy conversion applications.
Issue Date: 19-May-2021
Date of Acceptance: 1-Apr-2021
DOI: 10.1021/acsphotonics.1c00238
ISSN: 2330-4022
Publisher: American Chemical Society (ACS)
Start Page: 1469
End Page: 1476
Journal / Book Title: ACS Photonics
Volume: 8
Issue: 5
Copyright Statement: © 2021 The Authors. Published by American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Photonics, after peer review and technical editing by the publisher. To access the final edited and published work see
Sponsor/Funder: Engineering & Physical Science Research Council (E
Funder's Grant Number: EP/M013812/1
Keywords: 0205 Optical Physics
0206 Quantum Physics
0906 Electrical and Electronic Engineering
Publication Status: Published
Online Publication Date: 2021-04-26
Appears in Collections:Physics
Experimental Solid State