Enhancement and Switching of Fano Resonance in Metamaterial

Abstract

of resonant scattering phenomenon that makes asymmetric line shape originating from destructive interference between broadband scattering within a continuum state (bright superradiant mode) and an excitation of discrete state (dark subradiant mode) similar to coupled oscillator system. It was firstly observed in scattering phenomenon of electrons from helium atom by Ugo Fano. [2] Since then, Fano-type resonances have been studied in many physical systems including not only classical atomic systems but also nanophotonic systems such as the field of plasmonics, photonic crystals, and metamaterials due to its unique narrow and asymmetric line shapes nature. [3,4] Recently, Fano-type spectral response in plasmonic nanostructures and metamaterials have attracted considerable attention due to its superior capability to manipulate various characteristics of the Fano resonance in a broad frequency range, which is applicable for practical applications including chemical or biosensing, nonlinear optics, slow light device, and spectroscopy. [5,6] Numerous metallic or dielectric metamateirals have been designed to demonstrate Fano resonances using a common method of breaking the structural symmetry of nanostructures, such as split-ring resonators, [7] asymmetric double bars, [8][9][10] nanoparticle clusters, [11,12] dolmen structures, [13] and hybridized structures. [14][15][16][17] Despite the superior capability of the Fano resonant metamaterials, a trade-off between the quality factor (Q factor) and resonance intensity is unfortunately inevitable. Numerous high Q metamaterials have been proposed so far. [18][19][20] However, as the Q factor increases with an extremely narrow line width, the resonance intensity decreases simultaneously, causing it difficult to detect or distinguish sharp and minute resonances that limit application possibilities. It is an important issue of the high Q metamaterials and is being investigated in a way that defines the Figure of merit (FoM) as the product of the Q factor and intensity. [21] This approach, however, does not solve the tradeoff problem, but suggest only an appropriate region where the two values are moderately high by defining the FoM. The way to resolve the trade-off relation still remains a problem. In addition to the abovementioned problem related to the resonant nature of the Fano resonance, studies for controlling the resonance characteristics are also an important issue since it provides large tunability and flexibility for a variety of practical applications, such as optical sensor, elector-optic modulator, and ultrasensitive Excitation and manipulation of Fano resonances in plasmonic nanostructure have attracted considerable attention due to its capability of degrees of freedom in artificial design especially for spectral positions and quality factors (Q factors). To utilize the high Q factor of Fano resonances in practical applications, their sharp peaks or dips should be well detected, which means a high intensity of resonance line shape. Thus far, the realization of F...

Directional Fano Resonance in an Individual GaAs Nanospheroid

“…Fano resonance, a type of resonant scattering phenomenon which results in an asymmetric line‐shape, has been widely studied in the half past century . It promises applicability in a number of photonic devices, such as optical switches, filters, sensors, and so on. To date, Fano resonance has been achieved by various nanostructures like photonic crystals, plasmonic materials, and metamaterials .…”

High Q-Factor Hybrid Metamaterial Waveguide Multi-Fano Resonance Sensor in the Visible Wavelength Range

“…Supported by metal nanostructures in the sub-wavelength range, LSPR has a large local electromagnetic field enhancement effect [ 1 , 2 ], to be applied to surface-enhanced Raman scattering [ 3 , 4 ], electromagnetic induction transparency (EIT) [ 5 , 6 , 7 ], and in other fields. However, 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, thus resulting in the impracticality of potential applications based on surface plasmon resonance. In recent years, 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 ].…”

Dual-Fano resonances and sensing properties in the crossed ring-shaped metasurface

“…Local surface plasmon resonance (LSPR) is the collective oscillation of electrons excited by the incident light, which is confined at the surface of the metal nanoparticle [1][2][3]. The interaction among the different LSPRs on the adjacent nanoparticles can form the new normal modes on the surface of the nanoparticles, so many interesting phenomenon are observed based on the coupling between plasmonic resonance modes, such as plasmon induced transparency [4][5][6][7][8][9][10], Fano resonance [13][14][15][16], extraordinary optical transmission [17,18], breaking the optical diffraction limit [19,20], and so on.…”