Tailored Fano resonance and localized electromagnetic field enhancement in Ag gratings

Metallic gratings can support Fano resonances when illuminated with EM radiation, and their characteristic reflectivity versus incident angle lineshape can be greatly affected by the surrounding dielectric environment and the grating geometry. By using conformal oblique incidence thin film depositio...

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Bibliographic Details
Published in:Scientific reports 2017-03, Vol.7 (1), p.44335-44335, Article 44335
Main Authors: Li, Zhaozhu, Klopf, J. Michael, Wang, Lei, Yang, Kaida, Lukaszew, Rosa A.
Format: Article
Language:English
Subjects:
639/301/119/544
639/624/400/1021
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Electric fields
Electromagnetic fields
Electromagnetism
Fabrication
Humanities and Social Sciences
interfaces and thin films
MATERIALS SCIENCE
multidisciplinary
Nanophotonics and plasmonics
Resonance
Science
Surfaces
Thin films
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Summary:Metallic gratings can support Fano resonances when illuminated with EM radiation, and their characteristic reflectivity versus incident angle lineshape can be greatly affected by the surrounding dielectric environment and the grating geometry. By using conformal oblique incidence thin film deposition onto an optical grating substrate, it is possible to increase the grating amplitude due to shadowing effects, thereby enabling tailoring of the damping processes and electromagnetic field couplings of the Fano resonances, hence optimizing the associated localized electric field intensity. To investigate these effects we compare the optical reflectivity under resonance excitation in samples prepared by oblique angle deposition (OAD) and under normal deposition (ND) onto the same patterned surfaces. We observe that by applying OAD method, the sample exhibits a deeper and narrower reflectivity dip at resonance than that obtained under ND. This can be explained in terms of a lower damping of Fano resonance on obliquely deposited sample and leads to a stronger localized electric field. This approach opens a fabrication path for applications where tailoring the electromagnetic field induced by Fano resonance can improve the figure of merit of specific device characteristics, e.g. quantum efficiency (QE) in grating-based metallic photocathodes.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep44335