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Pronounced Linewidth Narrowing of Vertical Metallic Split-Ring Resonators via Strong Coupling with Metal Surface - PubMed

  • ️Fri Jan 01 2021

Pronounced Linewidth Narrowing of Vertical Metallic Split-Ring Resonators via Strong Coupling with Metal Surface

Wei Du et al. Nanomaterials (Basel). 2021.

Abstract

We theoretically study the plasmonic coupling between magnetic plasmon resonances (MPRs) and propagating surface plasmon polaritons (SPPs) in a three-dimensional (3D) metamaterial consisting of vertical Au split-ring resonators (VSRRs) array on Au substrate. By placing the VSRRs directly onto the Au substrate to remove the dielectric substrates effect, the interaction between MPRs of VSRRs and the SPP mode on the Au substrate can generate an ultranarrow-band hybrid mode with full width at half maximum (FWHM) of 2.2 nm and significantly enhanced magnetic fields, compared to that of VSRRs on dielectric substrates. Owing to the strong coupling, an anti-crossing effect similar to Rabi splitting in atomic physics is also obtained. Our proposed 3D metamaterial on a metal substrate shows high sensitivity (S = 830 nm/RIU) and figure of merit (FOM = 377), which could pave way for the label-free biomedical sensing.

Keywords: magnetic plasmon resonances; metamaterial; split-ring resonators; ultranarrow-band hybrid mode.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1

(a) Schematic view of the array of the Au VSRRs structure directly on the Au substrate. (b) The magnified front views of a unit cell of the Au VSRRs array.

Figure 2
Figure 2

The calculated reflection of Au VSRRs on Au substrate and transmission of Au VSRRs on silica substrate. (I) denotes the MP resonance and (II) denotes the narrowband mixed mode of the Au VSRRs on Au substrate. (III) denotes the transmission dip of the SRR on a silica substrate.

Figure 3
Figure 3

Normalized magnetic field (H/Hin) and electric field (E/Ein) distributions on the xoz plane for the dip I (a) and dip II (b) of the Au VSRRs on Au substrate and for the dip III (c) of the Au VSRRs on silica substrate.

Figure 4
Figure 4

The dependence of the reflection dip positions (I) and (II) on the period P. The positions of the MP resonance (solid black line) and the SPPs (solid blue line) are also presented.

Figure 5
Figure 5

The calculated reflection spectra of the Au VSRRs on Au substrate (a) for different prong length lz (b) for different length of base rod lx at normal incidence and (c) for different width w of the Au split-ring resonators.

Figure 6
Figure 6

(a) The calculated normal-incidence reflection spectra of the Au VSRRs on Au substrate with TM polarization immersed in different environment media. (b) The resonance wavelength of the dip II extracted from (a) as a function of refractive index.

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