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Highly efficient Metamaterials are necessary for applications in sensing, communication, etc. Fano resonance and electromagnetically induced transparency-like phenomena are essential for obtaining high Q-factor and sensitive Metamaterials. Employing both numerical simulations and experimental analysis, we investigate the emergence of Fano resonance in cross-resonator Metamaterials facilitated by the conductive coupling between dark and bright resonators. We analyze the gradual shift of the fano resonance by tuning the dark resonator and finally form an electromagnetically induced transparency-like transmission peak. The strong coupling of the resonator is observed in the form of an anti-crossing and discussed through analytical models. We demonstrate that the coupling strength of the dark and bright resonance in our metamaterial is proportional to the asymmetry parameter, albeit at the cost of the Fano resonance's Q-factor. The findings and methods introduced in this study can be used to develop highly efficient THz Metamaterials for various applications operable in room conditions. [ABSTRACT FROM AUTHOR]

A nanoantenna with Fano response is designed with plasmonic oligomers as a refractive index sensor to enhance surface-enhanced Raman scattering (SERS) in the visible light spectrum. The scattered radiation and field-enhanced interactions of the outer gallium phosphide (GaP) nanoring assembled with an inner heptamer of silver with Fano response are investigated systematically using the finite element method. The characteristics of Fano resonance are found to depend on the size, shape and nature of the materials in the hybrid nanoantenna. The confined electromagnetic field produces a single-point electromagnetic hotspot with up to 159.59 V/m. The sensitivity obtained from the wavelength shift and variation in the scattering cross-section (SCS) shows a maximum value of 550 nm/RIU. The results validate the design concept and demonstrate near-field enhancement, enabling the design of high-performance nanoantennas with enhanced optical sensing and SERS properties. [ABSTRACT FROM AUTHOR]

In this paper, a metal–insulator-metal (MIM) plasmonic absorber consisting of asymmetric double bars with bent arms located on top of a silica layer coated on a metal film is proposed, and its resonant features are analyzed. The suggested structure supports both Fano and dipole perfect absorption resonances at the near-infrared region (NIR). The asymmetry introduced into the structure can be induced by changing the bending angle or rotation angle of one of the antennas, while the other one remains fixed. Simulation results demonstrate that by applying both asymmetry factors to the structure, one can have two individual Fano peaks at the same time. It is shown that the magnitude, central wavelength, and line width of the Fano peaks are adjustable by controlling the geometrical parameters of the structure. It is also indicated that the quality factor (Q-factor) of the Fano resonance is inversely related to the degree of asymmetry introduced into the structure. According to the simulations, an ultra-narrow resonance peak with a bandwidth of 1.87 nm at the wavelength of 710 nm (corresponding to a Q-factor of 387) can be obtained by controlling the geometrical parameters. It is also discussed that the absorptivity of Fano and the dipole peaks can be adjusted inversely, by manipulating the grapheme chemical potential. The ratio of the absorptivity to the chemical potential of graphene about 275%/eV and 226%/eV is calculated for the Fano peak and dipole peak, respectively. Accordingly, the presented structure is an adjustable NIR absorber with a fully tunable absorption spectrum which can be utilized in various applications from tunable reflectors and photo-detectors to ultra-narrowband and broadband optical modulators. [ABSTRACT FROM AUTHOR]

In this paper, a plasmonic metasurface is proposed and designed that has switching capability and it can be used as a quantum switch as well as an optical sensor. To provide the switching characteristic, Kerr material is used with dimer split ring resonator. The Kerr material is considered to change the response from Fano to Lorentzian shape, thus two logical values of 0 and 1 can be made at the Fano dip resonance. The Characteristic Mode Theory is investigated to predict the occurrence of the Fano response with exact wavelength. The study shows that Fano response appears when the phase of CMT modes is around 90°. As a result, the Kerr material can impact the phase of CMT modes, that makes switching characteristic for the proposed metasurface, by reducing the phase value to 40° for various Kerr material implementation in the metasurface. Also in this paper, using eigenvalues, the exact location of the Fano response, was obtained and bright and dark modes are detected without plotting characteristic currents. The proposed metasurface is developed for optical sensing with high sensitivity as a part of optical and quantum spectroscopy. The sensitivity of the sensor is obtained around 400 nm/RIU which is sufficient to distinguish the materials and to have high resolution. [ABSTRACT FROM AUTHOR]

Optical Metasurfaces, two-dimensional nano-patterned surfaces designed to manipulate light, show promise for the sensitive detection of viruses. This paper reports on the development of a fractal plasmonic Metasurface tuned to operate in the near-infrared optical spectrum (2000–5000 nm) with Fano resonances. Fano resonances allow for sharper spectral features and higher sensitivity compared to typical plasmonic resonances. The Metasurface consists of a main ring containing self-similarly arranged nanoscale rings and disks while four smaller rings placed in the cardinal directions with five disks in the gaps between them. This fractal-like geometry exhibits enhanced light-matter interactions due to multiple electromagnetic hotspots in the structure. Specifically, simulations indicate the nanostructured sensor may enable label-free detection of viruses with high specificity by exploiting subtle changes in optical response when viral particles bind to receptors on the Metasurface. The simulation is done with full wave method of Finite integrated technique (FIT). The effect of the virus position over the Metasurface and its physical condition on the response of the Metasurface including the phase and amplitude is studied as a factor for sensing which can be used for optical imaging. • A highly sensitive biosensor based on a fractal plasmonic metasurface tuned to operate in the near-infrared optical spectrum (2000–5000 nm) with Fano resonances is designed. • Fano resonances allow for sharper spectral features and higher sensitivity compared to typical plasmonic resonances. • This fractal-like geometry exhibits enhanced light-matter interactions due to multiple electromagnetic hotspots in the structure. • This structure can be used for virus detection. [ABSTRACT FROM AUTHOR]

the mid-infrared metasurfaces play an important in optical applications including sensing and having Fano response is a benefit in this field for many goals including biosensing. So, these points are considered in this study and self-similar Plasmonic metasurface is suggested for sensing application. The suggested structure has a symmetrical formation but non-similar elements are considered to raise the Fano response. The structure contains five rings while the central one has a larger dimension than the four elements surrounding the central ring as an array of rings. The interaction of bright modes for both elements of the central ring and the array elements makes the Fano response at 1850 and 1910 nm while the single central ring has resonance at 1910 nm and the array rings have resonance at 1850 nm. The interaction of the element enhances the Q-factor of both resonances. The Full-wave method finite integrated technique (FIT) is used for modeling as a time domain method and the couple mother theory (CMT) is used for the analytical model. This metasurface is implemented as a sensor for detecting material under test and the sensitivity of the sensor is obtained 282 nm/RIU (Refractive Index Unit). Finally, the tissue of the liver as healthy and cancer cells are considered for examining the quality of the sensor. • The proposed design incorporates asymmetric ring elements inspired by self-similarity to induce Fano resonances. • Numerical simulations and analytical modeling demonstrate complete absorption at the target wavelengths of 1850 nm and 1910 nm. • A high sensitivity of 282 nm/RIU is attained owing to the narrow Fano resonance bandwidth. • The capability of this metasurface for non-invasive cancer detection and lab-on-chip integration is shown. • This paper provides an optimized design for plasmonic biosensors and results fitted with numerical model of the CMT. [ABSTRACT FROM AUTHOR]

Most electromagnetic phenomena pertaining to metamaterials are observed at the resonance positions. In this review, we have collated and analyze the most prevalent forms of resonance-based phenomena observed in metamaterials to serve as a ready reference for future researchers. Our focus will be on metamaterials operating at the terahertz frequency domain. Starting with the origin and evolution of fundamental LC resonances in metamaterials, we would explain occurrence of typical even and odd higher order resonance modes. We have also discussed Fano resonances in asymmetric gap resonators-based metamaterials. Further, quantum phenomena analogues, such as, electromagnetically induced transparency (EIT) or Plasmon Induced Transparency (PIT), which can significantly influence the metamaterials resonances are also discussed. Thereafter, origins to ultra-sharp resonances in toroidal metamaterials, along with chiral metamaterials and resonance mode hybridization effects in the context of terahertz metamaterials are described. This review should be useful for undertaking. [ABSTRACT FROM AUTHOR]

Plasmonic characteristic has been implemented for optical enhancement and the Fano resonance is noticed based on the interaction of the dark and bright mode at nano particle and for more enhancement, the second harmonic generation and multi Fano have been suggested. In this paper, we have designed a nano-antenna based on plasmonic, Fano, multi Fano and SHG modes and for this aim we have developed a single ring nano-particle with one and two split ring resonator elements for arousing multi Fano (SHG mode). Exactly, by arousing the Fano and multi Fano modes, the Extinction Cross Section is reduced in comparison with Plasmonic mode based on concentrating energy in the near field. We have shown that the angles of polarization have no effect on the extinction cross-section in multi Fano structure and it is independent of the polarization angle. We have revealed that how the multi Fano would be useful for light trapping and energy harvesting. We have obtained the wider bandwidth for the electric field in comparison with plasmonic and Fano structures which makes our proposed structure useful in energy harvesting applications such as solar cell at higher frequency ranges and an active area for wider bandwidth is achievable. For spectroscopy and optimal imaging, the figure of merit (FOM) is considered as a quality meter for the optical particles. The (FOM) of the external biological materials are compared for all three prototyped plasmonic, Fano and multi Fano structures. [ABSTRACT FROM AUTHOR]

Field enhancement in Plasmonic and FANO mode at nano antennas are noticed recently, here, we are modeled a nano antenna for achieving Fano resonance and for this aim, we are made asymmetric formation in nano ring structure and studied the parametric effects on Fano resonance controlling. We have debated on E-field enhancements at resonances with comparison the parameters effect on Fano resonance energy. We show that the single ring has plasmonic mode and adding an inner ring made Fano resonance and shows that the energy in dark mode is increased drastically. Here, the study of the inner ring position is indicated that how the bright mode and dark mode have appeared in nano antenna. Figure of merit (FOM) is studied for different additional material effects on prototype structure and Δ(E) variation is noticed. The structure is modeled with FDTD simulation by the CST microwave studio and for substrate; we selected SiN with a thickness of 40 nm. Here for achieving dark mode energy, novel shape of the dual ring nano antenna is suggested for concentration of the energy in small point to increase the interaction between nano particle and bio-particle. [ABSTRACT FROM AUTHOR]

Chiral metamaterials with asymmetric transmission can be applied as polarization-controlled devices. Here, a Mie-based dielectric metamaterial with a spacer exhibiting asymmetric transmission of linearly polarized waves at microwave frequencies was designed and demonstrated numerically. The unidirectional characteristic is attributed to the chirality of the metamolecule and the mutual excitation of the Mie resonances. Field distributions are simulated to investigate the underlying physical mechanism. Fano-type resonances emerge near the Mie resonances of the constituents and come from the destructive interference inside the structure. The near-field coupling further contributes to the asymmetric transmission. The influences of the lattice constant and the spacer thickness on the asymmetric characteristics were also analyzed by parameter sweeps. The proposed Mie-based metamaterial is of a simple structure, and it has the potential for applications in dielectric metadevices, such as high-performance polarization rotators. [ABSTRACT FROM AUTHOR]

We propose a planar metamaterial formed by four-strip metallic resonators, which can achieve high-Q Fano resonance in terahertz regime. This terahertz planar metamaterial supports a sharp Fano resonance at 0.81 THz with 25% transmission. The resonance bandwidth of the dip is 0.014 THz with the Q-factor of 58. The interference between the bright mode and dark mode leads to the Fano line shape. This sharp Fano profile is explained by the electromagnetic theory of Fano resonance. Moreover, multiple Fano resonances can be realized by adding more strips into the original structure. As an example, two Fano dips with Q-factors of 61 and 65 can be achieved via a five-strip structure. [ABSTRACT FROM AUTHOR]