期刊
ACS NANO
卷 6, 期 7, 页码 6492-6506出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn3022684
关键词
plasmonics; blunt nanostructures; transformation optics; broadband light harvesting; Fano resonance
类别
资金
- Lee family scholarship
- European Community [213390]
- U.K. Engineering and Physical Sciences Research Council (EPSRC)
- Leverhulme Trust
- Engineering and Physical Sciences Research Council [EP/H000917/1, EP/D063329/1, EP/H000917/2] Funding Source: researchfish
- EPSRC [EP/D063329/1, EP/H000917/2, EP/H000917/1] Funding Source: UKRI
The sharpness of corners/edges can have a large effect on the optical responses of metallic nanostructures. Here we deploy the theory of transformation optics to analytically investigate a variety of blunt plasmonic structures, including overlapping nanowire dimers and crescent-shaped nanocylinders. These systems are shown to support several discrete optical modes, whose energy and line width can be controlled by tuning the nanoparticle geometry. In particular, the necessary conditions are highlighted respectively for the broadband light absorption effect and the invisibility dips that appear in the radiative spectrum. More detailed discussions are provided especially with respect to the structures with asymmetric edge rounding. These structures can support additional subradiant modes, whose interference with the neighboring dipolar modes results in a rapid change of the scattering cross-section, similar to the phenomenon observed in plasmonic Fano resonances. Finite element numerical calculations are also performed to validate the analytical predictions. The physical insights into blunt nanostructures presented in this work may be of great interest for the design of broadband light-harvesting devices, invisible and noninvasive biosensors, and slowing-light devices.
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