Near- And Far-Field Investigation Of Dark And Bright Higher Order Resonances In Square Loop Elements At Mid-Infrared Wavelengths

Abstract

Three different size gold square loop structures were fabricated as arrays on ZnS over a ground plane and designed to have absorptive fundamental, second order, and third order resonances at a wavelength of 10.6 ìm and 60° off-normal. The angular dependent farfield spectral absorptivity was investigated over the mid-infrared for each size loop array. It was found that the second order modes were dark at normal incidence, but became excited at off-normal incidence, which is consistent with previous work for similar geometry structures. Furthermore, near-field measurements and simulations at a wavelength of 10.6 ìm and 60° off-normal showed that the second order mode (quadrupolar) of the medium size loop yielded a near-field response similar in magnitude to the fundamental mode (dipolar) of the small size loop, which can be important for sensing related applications where both strong near-field enhancement and more uniform or less localized field is beneficial.

Publication Date

3-6-2017

Publication Title

Optics Express

Volume

25

Issue

5

Number of Pages

5594-5608

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1364/OE.25.005594

Socpus ID

85015760997 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85015760997

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