Efficient third harmonic generation and nonlinear subwavelength imaging at a higher-order anapole mode in a single germanium nanodisk.

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Title: Efficient third harmonic generation and nonlinear subwavelength imaging at a higher-order anapole mode in a single germanium nanodisk.
Authors: Grinblat, G
Li, Y
Nielsen, MP
Oulton, RF
Maier, SA
Item Type: Journal Article
Abstract: Benefiting from large intrinsic nonlinearities, low absorption, and high field enhancement abilities, all-dielectric nanoantennas are considered essential for efficient nonlinear processes at subwavelength volumes. In particular, when the dielectric nanoantenna supports the nonradiating anapole mode, characterized by a minimum in the extinction cross section and a maximum electric energy within the material, third harmonic generation (THG) processes can be greatly enhanced. In this work, we demonstrate that a higher-order anapole mode in a 200 nm thick germanium nanodisk delivers the highest THG efficiency on the nanoscale at optical frequencies. By doubling the diameter of a disk supporting the fundamental anapole mode, we discover the emergence of an anapole mode of higher order, with a valley in the extinction cross section significantly narrower than that of the fundamental anapole. Under this condition, we observe a highly improved electric field confinement effect within the dielectric disk, leading to THG conversion efficiencies as large as 0.001% at a third harmonic wavelength of 550 nm. In addition, by mapping the THG emission across the nanodisk, we are able to unveil the anapole near-field intensity distributions, which show excellent agreement with numerical simulations. Our findings remarkably expand contemporary knowledge on localized modes in dielectric nanosystems, revealing crucial elements for the elaboration of highly efficient frequency upconversion nanodevices.
Issue Date: 15-Dec-2016
Date of Acceptance: 15-Dec-2016
URI: http://hdl.handle.net/10044/1/43982
DOI: https://dx.doi.org/10.1021/acsnano.6b07568
Publisher: American Chemical Society
Start Page: 953
End Page: 960
Journal / Book Title: ACS Nano
Volume: 11
Issue: 1
Copyright Statement: © 2016 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano after peer review and technical editing by the publisher. To access the final edited and published work see https://dx.doi.org/10.1021/acsnano.6b07568
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (E
Office Of Naval Research (USA)
Funder's Grant Number: EP/L024926/1
Keywords: all-dielectric nanodisks
anapole modes
electric field enhancement
nonlinear imaging
third harmonic generation
Nanoscience & Nanotechnology
MD Multidisciplinary
Publication Status: Published
Conference Place: United States
Appears in Collections:Physics
Experimental Solid State
Faculty of Natural Sciences

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