Dual Fano Resonances Research Articles

Dipole coupling and dual Fano resonances in a silicon nanodimer

We demonstrate theoretically in this work the existence of dual Fano resonances in a silicon nanodimer, which result from the strong coupling between the magnetic dipole in one nanocylinder and the electric dipole in another. It is shown that the intensities of the Fano resonances can be controlled by changing the polarization of the incident light, and the wavelengths of the resonances can be shifted by varying the separation of nanocylinders. And a broadband scattering response is also presented. These results concerning the ohmic loss-less, easily fabricated silicon nanodimer may have promising applications in wave filters, solar cells, biosensing, etc.

Single/Dual Fano Resonance Based on Plasmonic Metal-Dielectric-Metal Waveguide

A plasmonic metal-dielectric-metal (MDM) waveguide structure is proposed by placing a slot cavity below or above a groove. The groove and the slot cavity can act as a reflector and a resonator, respectively. Due to the interactions between the broad dark mode and the narrow bright mode caused by the groove and the side-coupled slot cavity, single Fano resonance with sharp asymmetric spectral profile is achieved. Interestingly, dual Fano resonances can also be obtained by using two different slot cavities, which are simultaneously distributed on both sides of the groove. The line shape can be transformed by changing the length of the groove, while the wavelength of the resonance peak can be manipulated linearly with the length of the slot cavity. The proposed structure yields a highest sensitivity of ∼1131 nm/RIU and a figure of merit of ∼1.6 × 107, and thus, we believe that it can serve as an on-chip nanosensor.

Tunable Fano Resonances and Electromagnetically Induced Transparency in All-Dielectric Holey Block

The optical properties of a simple planar silicon nanoblock with cylindrical hole operating at terahertz (THz) frequencies are investigated. The proposed nanostructure exhibit low loss electromagnetically induced transparency (EIT) and Fano resonances, which arises due to the near-field coupling between the nanoblock and cavity modes. The line shape of these resonances can be considerably modified and tuned by varying the geometrical parameters. Furthermore, the symmetry breaking conception is also introduced, which enables higher-order dark hybridized modes to interact with each other, resulting in a dual EIT and Fano resonances in the optical spectrum. The EIT and Fano resonances present high local field enhancement (33) and Q-factors (584) due to extremely low absorption loss. This makes the proposed design an ideal platform for low loss slow-light devices and multi-wavelength biosensing applications.

Fano Resonance with Ultra-High Figure of Merits Based on Plasmonic Metal-Insulator-Metal Waveguide

A plasmonic nano-sensor is proposed by means of Fano resonance in a metal-insulator-metal (MIM) waveguide structure, which consists of two identical slot cavities placed nearby two symmetrical grooves in a MIM bus waveguide. Due to the interaction of the broad bright mode and the narrow dark mode caused by the grooves and the side-coupled slot cavities, respectively, the transmission spectrum possesses a sharp asymmetrical profile. The spectral line shape can be manipulated by changing the length of the grooves, and the wavelength of the resonance peak has a linear relationship with the length of the slot cavity. These characteristics offer flexibility to design the device. This nano-sensor yields a sensitivity of ~903 nm/RIU and a figure of merit (FOM) of ~3.1 × 105. Besides, dual Fano resonance peaks are also achieved by shifting the slot cavities away from the center of the grooves, resulting in a FOM as high as 4.6 × 105. The proposed structure may find important applications in the on-chip nano-sensing area.

Ultralow-power all-optical tunable dual Fano resonances in nonlinear metamaterials

Dual Fano resonances are realized in a nonlinear photonic metamaterial consisting of periodic arrays of asymmetrical meta-molecules etched in a gold film coated with azobenzene polymer layer made of poly[(methyl methacrylate)-co-(disperse red 13 acrylate)]. Enormously enhanced photoisomerization associated with resonant excitation brings about a large refractive index variation in the azobenzene polymer. Under excitation of a weak pump light as low as 0.61 kW/cm2, a large shift of 50 nm in the Fano resonance wavelength is obtained. Compared with previous reports, the threshold pump intensity is reduced by seven orders of magnitude while a large tunability is maintained simultaneously.

Double Fano resonances due to interplay of electric and magnetic plasmon modes in planar plasmonic structure with high sensing sensitivity

Double Fano resonant characteristics are investigated in planar plasmonic structure by embedding a metallic nanorod in symmetric U-shaped split ring resonators, which are caused by a strong interplay between a broad bright mode and narrow dark modes. The bright mode is resulted from the nanorod electric dipole resonance while the dark modes originate from the magnetic dipole induced by LC resonances. The overlapped dual Fano resonances can be decomposed to two separate ones by adjusting the coupling length between the nanorod and U-shaped split ring resonators. Fano resonances in the designed structure exhibit high refractive-index sensing sensitivity and figure of merit, which have potential applications in single or double-wavelength sensing in the near-infrared region.