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(Colour on-line) Extinction spectra of (a) nanodisk, corresponding to the case of , (b) nanoring, corresponding to the case of . The insets present the corresponding electric field and charge density distributions. The red and blue colour represents the positive and negative charge, respectively. The colour bars represent the amplitude of , where E is the local electric field near the nanodisk or nanoring, and E0 is the incident electric field.
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Fano resonances have been achieved in a variety of complex plasmonic nanostructures. Here we propose a novel planar structure supporting higher order Fano resonances, a plasmonic nanodisk with a built-in missing sectorial slice whose slice angle varies from 0 to 360◦. The numerical results reveal that higher order Fano resonances can be generated i...
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Citations
... Multi-Fano modes are attained by rotating the two-split nanorings in opposite directions. In comparison with the previously reported designs [28][29][30][31][32][33][34][35], our work demonstrates highly sharp Fano resonances in relatively simple geometry. A detailed comparison table will be given between reported research work in the literature and ours in the section above the conclusion section about the quality factor (Q), full width half maximum (FWHM), sensitivity (S), figure of merit (FoM), and minimum detectable refractive index change (Dn min ). ...
We theoretically propose a sensitive label-free sensor with high figure of merit (FoM) based on Fano resonances on a plasmonic metasurface whose unit cell consists of double two-split nanorings by finite-element method. The unit cell of the proposed Fano resonant structure comprises of two thin gold nanorings each with two splits. Two Fano modes are generated in near-infrared regime through symmetry breaking by rotating the splits in nanorings in opposite directions. The fundamental feature of the proposed sensor is its relatively simple structure, double-mode usable, a large single-side quality factor of 566, and high FoM value of 378. According to our knowledge, these values are higher than those previously reported. The sensor has high substance resolving capability that its minimum detectable refractive index change can be as small as 0.00236, making it possible to distinguish different bio-tissues.
... 利用有限元方法计算三聚体的吸收谱时, 采用了完 美匹配层假设, 这时被三聚体所散射的光会被完美 匹配层所吸收 [32] . 在本文中我们主要考察了三聚 体结构中金属材料的吸收光谱、电场和电荷分布, 其吸收是利用计算热损的方法获得的. ...
The localized surface plasmon resonance can be generated on the surface of the nano-metamaterial by the interaction between the nano-metamaterial and the light field, and also many plasmon oscillation modes can occur in the process of the hybridization between many infinitesimal composite structures, which is widely used for adjusting the resonant frequency in the optical frequency domain. Recently, analogue of the electromagnetically induced transparency(EIT) has been realized in the low-loss nano-metamaterial, and is well known as the plasmon induced transparency(PIT). In atomic physics, EIT is an effect which originates from the destructive quantum interference of two different excitation pathways. A sharp dip of nearly ideal transmission can arise within the broad absorption profile, which indicates that the EIT can be used in the fields of slow slight, delay lines and low-loss metamaterial. In this paper, a trimer consisting of a vertical nanorod(serving as a dipole antenna) and two parallel nanorods(used as a quadrupole antenna) is employed to investigate the process mechanism of the PIT in detail. It is found that the vertical nanorod with a large broad linewidth can be strongly coupled with the light. However, the parallel nanorods are weakly coupled with the light and their narrow linewidths are almost from the intrinsic metal loss(Drude damping) that is much smaller than the radiative damping of the dipole antenna. These two antennas can be strongly coupled due to their close similarities. Moreover, the absorption spectra of the trimer obtained by using three-dimensional finite element method vary with its coupling distance and geometry size, and the dipole bright mode corresponding to the dipole antenna splits under the action of the dark mode for the quadrupole antenna. Thus, a fresh physical interpretation is given: the PIT is mainly due to the coherent superposition after the splitting of the dipole oscillation mode in the vertical nanorod, rather than the parallel nanorods. Taking into consideration the phase correlation associated with coupling process of two oscillators, we introduce a modified Lorentzian oscillator model to investigate the effects of the coupling phase factor on the modulation of the absorption spectra and the coherent superposition between the splitting bright modes on the PIT. These findings will provide theoretical references for the applications of artificial atom, optical switching and slow light devices designed in the nanosize range.
... Although plasmonic defective nanodisk structures were presented in the optical range [15,16] and focus on Fano resonance for grazing incidence, in this paper, on the basis of the structure in [13], we propose a coaxial defective-disk and ring structure (DDRS), which focuses on the coupling between the inner defective disk and the outer ring in the DDRS for normal incidence in THz range. When a defective component is embedded in the disk, an improved dipole mode at a higher frequency in the wedged-shaped slice is produced, which leads to an enhanced coupling between the inner disk (defective disk) and the outer ring. ...
We have illustrated the localized plasmonic properties on the terahertz region based on a coaxial disk and ring structure (DRS) and a defective-disk and ring structure (DDRS). Two resonances can be observed in these coaxial structures, which arise from the anti-bonding and bonding resonance hybridization. Compared with DRS, an enhanced localized plasmonic effect at a higher-frequency resonance is observed on the DDRS, which is owing to a new strong dipole mode evoked at the edge of the wedge-shaped slice. Moreover, this higher-frequency localized plasmonic resonance of the DDRS could be further enhanced by increasing the depth of the wedge-shaped slice due to the coupling between the dipole resonance of the deeper wedge-shaped slice and the outer ring. Therefore, by using higher-order enhanced localized plasmonic characteristics, the designed DDRS is promising in sensing, spectroscopy and slow light effect.
... Besides, similar to the symmetric dual-disk ring (SDDR) proposed by Yuan Hsing Fu and co-workers [29], the symmetric dual nanoellipsoid in the cavity of the ring (SDNECR) also can suppress the quadrupolar and the hexadecapolar Fano resonances (FRs) and enhance the octupolar and the triakontadipolar modes. Although some nanostructures [30][31][32][33] have been designed and studied, our current work aims at providing a new nanostructure to achieve the Fano resonances based on the plasmon resonance tunabilities of nanoellipsoids and nanorings. We hope the concentric single nanoellipsoid rotation in the cavity of the ring (CSNERCR), nonconcentric single nanoellipsoid in the cavity of the ring (NCSNECR), and the asymmetrical dual nanoellipsoid in the cavity of the ring (ADNECR) would find applications in multiwavelength surface-enhanced spectroscopy and optical switch. ...
Surface plasmon resonances of an ellipsoid-ring nanostructure with spatial symmetry breaking have been investigated theoretically. In this plasmonic system, the multiple Fano resonances are enhanced and can be tuned effectively by rotating the nanoellipsoid in the cavity of the ring. It is demonstrated that such multiple Fano resonances result from the plasmon coupling between the bright mode of the nanoellipsoid and the dark mode of the nanoring. The dark octupolar and the bright octupolar Fano resonances can be excited by modifying the geometrical parameters of the nanostructure. The asymmetry also allows the generation of strong electric field enhancements in this nanostructure which can be applied in the surface-enhanced spectroscopy.
... Therefore, an important application of nanoring is for SERS. Although multiple Fano resonances have been gained in previous work [32][33][34][35][36], the present work aims at proposing a novel strategy for the generation of higher order Fano resonances based on double symmetry breaking. Therefore, we proposed an interesting disk-ring nanostructure with double symmetry breaking (the nanoring is asymmetric and the nanodisk is displaced with respect to the center of the nanocavity). ...
Optical properties of disk-ring plasmonic nano-structures with double symmetry breaking are investigated theoretically. Tunable higher order Fano resonance is achieved, and it is sensitive to the degree of asymmetry of the nanoring, the offset and the dimension of the nanodisk. It is demonstrated that such higher order Fano resonances orig-inate from the destructive interference between the bright mode of the displaced nanodisk and the dark mode of the asymmetric nanoring. By tunning the asymmetry degree of the nanoring, the offset, and the dimension of the nanodisk, certain higher order Fano resonances can be suppressed or enhanced. Double asymmetry breaking also allows the reali-zation of the stronger electric field enhancement, resulting from the stronger interaction between the displaced nanodisk and the asymmetric nanoring.
Fano resonance (FR) owns a sharp asymmetric line shape, low radiation loss and huge modification ability so that enhancing Fano resonance in asymmetric dimers is a topic of interest in nanophotonics and plasmonics. Here, we theoretically investigated the enhancement and tunability of Fano resonance in shape-asymmetric gold nanoring-nanodisk dimer through varying the size of nanodisk (ND) and polarization angle (θ). Furthermore, we studied the performance of FR in terms of the quality factor (Q F) and figure of merit (FoM). We explored the sensitivities of FR with maximum FoM to assess the capability of this mode in the detection of refractive index. Moreover, our design displays enhanced performance by increasing size of ND and polarization angle of the incident light offering another degree of freedom for exploring and modulating asymmetric dimers. This approach provides insights into the enhanced and tunable FR with remarkable potential in sensing and switching applications.
A silver nanostructure consisting of double sectors is proposed in this paper. In addition, the plasmon resonance and electric field enhancement have been investigated theoretically. It is found that, in this structure, the multiple resonances produce, which is tunable by the parameter of the structure. The localized electromagnetic fields can be produced at the tips of the structure. In addition, the enhanced electromagnetic fields can be observed between the sectors in a wide scale at the lower energy peak. The result of the investigation has great significance for the production of practical nanostructures and the improvement of possible applications.
