Abstract
We propose a high quality-factor (Q-factor) multi-Fano resonance hybrid metamaterial waveguide (HMW) sensor. By ingeniously designing a metal/dielectric hybrid waveguide structure, we can effectively tailor multi-Fano resonance peaks’ reflectance spectrum appearing in the visible wavelength range. In order to balance the high Q-factor and the best Fano resonance modulation depth, numerical calculation results demonstrated that the ultra-narrow linewidth resolution, the single-side quality factor, and Figure of Merit (FOM) can reach 1.7 nm, 690, and 236, respectively. Compared with the reported high Q-value (483) in the near-infrared band, an increase of 30% is achieved. Our proposed design may extend the application of Fano resonance in HMW from mid-infrared, terahertz band to visible band and have important research value in the fields of multi-wavelength non-labeled biosensing and slow light devices.
Highlights
Localized surface plasmon resonance (LSPR) is a resonance phenomenon caused by the collective oscillation of free electrons on the surface of precious metal nanoparticles under the action of photons
A large number of studies have extensively conducted and deeply explored the optical nanodevices that excite ultra-high Q resonance lines to overcome this defect, mainly focusing on: the resonators of high refractive index dielectric materials related to bound or quasi-bound states in the continuum excite the Fano resonance of high Q-factor through strong coupling between modes [10,11,12,13,14,15], and the plasma lattice resonance and Fano resonance based on periodic structure [8,16,17,18,19,20,21]
In 2018, Chen et al focused on the dielectric flat waveguide composed of a two-dimensional gold nanoparticle array, and under the condition that the electric field in the waveguide mode was parallel to the polarization direction of LSPR, Fano resonance was achieved in the near-infrared spectra (NIR), and the sensitivity can reach 250 and 200 nm/RIU [37]
Summary
Localized surface plasmon resonance (LSPR) is a resonance phenomenon caused by the collective oscillation of free electrons on the surface of precious metal nanoparticles under the action of photons. Its quality factor (Q-factor) is relatively low (Q < 10) [8,9] to achieve ultra-narrow-band resonance due to the excessively high ohmic loss of the metal, resulting in the impracticality of potential applications based on surface plasmon resonance. In 2018, Chen et al focused on the dielectric flat waveguide composed of a two-dimensional gold nanoparticle array, and under the condition that the electric field in the waveguide mode was parallel to the polarization direction of LSPR, Fano resonance was achieved in the near-infrared spectra (NIR), and the sensitivity can reach 250 and 200 nm/RIU [37]. The strong coupling between the LSPR of the metal array and the different guided modes, which can produce extremely narrow bands of Fano resonance response with high Q-factor, were theoretically proven. This may have great potential in the field of label-free biochemical sensing and narrow-band detection in the visible light band
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