Magnetic Fano Resonances Research Articles

Magnetic Fano resonance enhanced second-harmonic generation in chiral hybrid bismuth halides

Magnetic Fano resonance provides a potential opportunity to control both linearity and nonlinearity of light for their low radiation loss and near-field enhancement. Previous investigations have demonstrated its significant enhancement of nonlinearity in a plasmonic structure and the 2D materials coupled to it. In this work, the enhancement of second harmonic generation (SHG) of hybrid bismuth halides at the important communication wavelength of 1550 nm with a magnetic Fano dip is theoretically studied. To this end, a hybrid system composed of two asymmetric silver square split rings (SSRs) and this chiral perovskite film is designed. The simulation results show that magnetic Fano-like resonance is induced at the destructive interface of two magnetic modes in the SSR dimer, which can be inherited to hybrid bismuth halides, thereby leading to the increase of four orders of magnitude in its SH near-field enhancement factor. With a peak intensity of 0.16 GW cm−2, the composite structure features a high SHG conversion efficiency of up to 1.6 × 10−3 at the Fano resonance position. By rotating the polarization angle of fundamental optical excitation, the emitted SHG signal is switched on–off. Our research provides a valuable thought for enhancing the nonlinear optical process of the perovskite films by coupling the magnetic modes.

Polarization‐Dependent Optical Forces Arising from Fano Interference

AbstractA Fano resonance originates from the resonant coupling between interacting multipoles inside nanostructures. It breaks the symmetry of spectral line shape and enables Fano‐resonant media to present unusual scattering properties. However, understanding the mechanical effects of such multipolar coupling systems is highly complex compared with the traditional simple dipole. In this work, using single Si nanospheres as the Fano‐resonant media, optical forces arising from different types of Fano resonances including the electric, magnetic, and magnetoelectric Fano resonances are investigated. It is shown that the directions of these types of forces are tunable in three dimensions. The necessary condition to realize a direction change of the Fano‐resonance‐induced forces and elucidate the underlying physics are presented. Furthermore, it is found that the Fano‐resonance‐induced forces exhibit strong polarization‐dependent properties which traditional optical (dipolar) forces cannot possess.

Magnetization dynamics in the YIG/Au/YIG magnon valve

The magnetization dynamics of an yttrium iron garnet (YIG)/Au/YIG magnon valve was investigated using broadband ferromagnetic resonance. The material characterizations of YIG/Au/YIG were performed using cross-sectional scanning transmission electron microscopy, x-ray diffraction spectroscopy, x-ray photoemission spectroscopy, Raman spectroscopy, and UV–visible spectroscopy. Asymmetric Fano resonance in the YIG/Au (60 nm)/YIG magnon valve structure was observed experimentally, and the two coupled oscillators model was used to describe the source of the Fano resonance qualitatively. We also provide a quantitative description of the Fano resonance and extract the Fano factor, which is an important feature that can be used to define the interaction sign. This represents the first attempt to apply the Fano resonance to magnetization dynamics. The spin wave resonance modes excited by the Au nanoparticles (NPs) surface plasmons were also observed in a YIG/Au NPs/YIG structure. Our findings confirm the occurrence of magnetic Fano resonance in the YIG/Au/YIG magnon valve and pave the way toward the development of quantum information devices based on magnon valves.

Tunable Magnetic Fano Resonances on Au Nanosphere Dimer–Dielectric–Gold Film Sandwiched Structure

The Fano resonance demonstrates excellent performance due to its narrow asymmetrical spectral line shape, and its sensitivity to structure and material parameter changes. Compared to conventional Fano resonances, the Fano resonance generated by the magnetic dipole is more advantageous because of its high absorption and low loss. In this study, we propose an Au nanosphere dimer–dielectric–gold film sandwiched structure that supports the magnetic Fano resonance mode. And the Fano resonance can be efficiently tuned from visible to near-infrared wavelength by changing the size of the gold nanospheres and the thickness of the dielectric layer. Different from the single gold nanosphere–dielectric–film structure, the results suggest that the proposed structure is sensitive to the polarization direction of the excitation light. Considering the above characteristics, the proposed structure can be applied in multi-band sensing, surface-enhanced Raman spectroscopy, and dynamically adjustable optical switches.

Gap-enhanced toroidal dipole and magnetic Fano resonances with polarization independence in all-dielectric metamaterials for sensing

We have designed and numerically analyzed gap-enhanced toroidal dipole (TD) and magnetic Fano resonances with high Q-factors and large modulation depths simultaneously in an all-dielectric metamaterial for sensing. By introducing a gap in the cylinder, we achieved a significant enhancement in Q-factor and electromagnetic field compared to the cylinder with no gap in near-IR regime. In addition, TD and magnetic Fano resonances can be tailored through varying width and position of gap and can be achieved without symmetry breaking, showing polarization-independent characteristics. Further, we theoretically demonstrated a multichannel refractive index (RI) sensor with bulk RI sensitivity exceeding 100 nm / RIU and figure of merit reaching 260. With high structural symmetry of the proposed metamaterial, it may find applications in lasing, nonlinear devices, and multiwavelength biomedical sensing.

Non-Equidistant Arrangement in All-Dielectric Quadrumers and Mirror-Symmetric One-Dimensional Photonic Crystals Hybridstructure for Self-Referenced Sensing Scheme

All-dielectric nanostructures have attracted attention for highly efficient light manipulation. Higher Q-factor Fano resonance can be excited due to the rich phenomenology of optical modes supported by high-index dielectric materials with low intrinsic material loss, including both electric and magnetic multipolar Mie resonances. So far, there have been few studies done on the sensing with Fano-resonant all-dielectric resonator nanostructures. Here, an all-dielectric self-referenced optical sensor is numerically demonstrated based on Si quadrumers and mirror-symmetric 1-D photonic crystals (1DPCs) hybridstructure, operating at the infrared wavelength range with higher sensing performance and much more stable reference signal. Magnetic Fano resonance and Fabry-Perot resonance were combined into such a hybridstructure for the first time. The influences of the gap distance, including Δx and Δy, on the coupling effects between the Si nanodimers along the polarization direction and the 1DPCs are systematically discussed. The sensing performance has been numerically investigated in different analytes with the sensitivity and figure of merit (FOM) of 760 nm/RIU and 1515 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> respectively, which paves the way to be a much more sensitive detection of small refractive index changes in an unstable environment and suggests potential applications in biological and chemical sensing.

基于单劈裂环-双劈裂盘结构的多重磁Fano共振

基于单劈裂环-双劈裂盘结构的多重磁Fano共振

Impact of intra- and inter-unit cell symmetry breaking on the optical response of the arrays of nanotrimers.

Understanding the impact of geometric changes on the properties of otherwise symmetric nanostructures is of essential importance for nanophotonics. In this Letter, we show that intra- and inter-unit cell symmetry breaking can substantially modify the optical properties of nanotrimers from both the experimental and simulation aspect. Specifically, shifting the location of one nano-dot within the trimer unit cell leads to the formation of magnetic Fano resonances with loop-like polarization patterns that are not present in the symmetric configuration. We further unlock the impact of lattice modification on the optical response of square arrays of trimers with broken three-fold rotation symmetry and with intra-trimer distances as small as 25nm, showing distinctively different spectral evolutions of the electric and magnetic Fano resonances. The results achieved highlight the symmetry breaking as an essential tool to unlock and strengthen predefined resonances, which can have important applications, particularly in the field of sensing.

Double Fano resonances and electromagnetically induced transparency-like optical response achieved by breaking the symmetry of two double-split rings

In recent years, various nanostructures related to Fano resonance have been proposed by many researchers due to their outstanding optical properties. A structure consisting of two double-split rings (TD-SR) is researched by using finite element method in this paper. When the incident light is normal to the structure surface, a magnetic Fano resonance can be generated by the interference of bright electric mode and dark magnetic mode. In addition, when the symmetry of the structure is destroyed along x-axis or y-axis, double Fano resonances will be generated. At the same time, the maximum refractive index sensitivity (S) and the maximum figure of merit at resonance mode can reach 1200 nm/RIU and 30.61, respectively. More interestingly, the electromagnetically induced transparency (EIT)-like behavior can be induced when the cavity of inner split ring is biased and the corresponding electric and magnetic field enhancements can reach 229 and 52, respectively. The optical properties of our nanostructure make it has important application value in the fields of multi-wavelength sensor, ultra-sensitive biosensor, surface enhanced spectroscopy and slow light.

The generation of multiple electric and magnetic Fano resonances in the prefect ring-triple arcs ring nanostructure

The electromagnetic field enhancement, multiple electric and magnetic Fano resonances in perfect ring-triple arcs ring (PR-TAR) nanostructure are studied by using finite element method. In this nanostructure, electric and magnetic Fano resonances can be promoted as a result of the coupling between dark modes of the perfect ring (PR) and bright modes of the triple arcs ring (TAR). New multiple electric and magnetic Fano resonances are obtained by changing the central angle or the thickness of the up arc. Multiple new resonance modes can be generated by offsetting the center of the TAR. According to the calculation results, the electric and magnetic fields are both enhanced greatly. The highest electric and magnetic field enhancements reached 409 and 48.7, respectively. These characteristics of the PR-TAR nanostructure have potential applications on the propagation of low-loss plasmons, surface enhanced plasmon spectroscopy, multi-wavelength spectrometer and multi-control Fano switch.

Symmetry-breaking induced magnetic Fano resonances in densely packed arrays of symmetric nanotrimers

Due to unique properties and great design flexibilities, Fano resonances represent one of the most promising optical features mediated by metallic nanostructures, while the excitation of some Fano modes is impossible due to symmetry reasons. The aim of this work is to show that dense lattice arrangements can have a profound impact on the optical properties of nanostructures and, in particular, can enable the excitation of otherwise dark modes. Here, we demonstrate this concept using the example of rectangular arrays of symmetric trimers packed so densely that the coupling between neighbouring unit cells imposes a symmetry break, enabling the excitation of magnetic Fano resonances. We found that in experiments as well as in simulations, electric and magnetic Fano resonances can be simultaneously formed in cases where the inter-trimer distances are sufficiently small. By analysing the transition from an isolated trimer mode into a regime of strong near-field coupling, we show that by modifying the rectangular unit cell lengths due to the symmetry mismatch between lattice and trimer, two types of Fano resonances can be found, especially magnetic Fano resonances with loop-type magnetic field distributions within the centre of each trimer, which can be either enhanced or suppressed. In addition, the influence of the refractive index environment was measured, showing sensitivity values of approximately 300 nm/RIU. Our work provides fundamental insights into the interaction of the lattice and nanostructure response and paves the way towards the observation of novel optical excitations.

Superlattice bilayer metasurfaces simultaneously supporting electric and magnetic Fano resonances

In this paper, we demonstrated a Fano resonant superlattice metasurface structure composed of bilayer trimeric metallic stripes in each unit cell. It can simultaneously support two types of Fano resonances, which individually possesses electric and magnetic properties at microwave frequencies, respectively. The electric Fano resonance is generated by the anti-phase electric mode interfering with in-phase electric mode, while the magnetic Fano resonance stems from the interference between the magnetic modes in the gap area and the anti-phase electric mode in each layer of the bilayer metasurface. In addition, the double Fano resonances are readily tunable by adjusting a variety of distance degrees of freedom in the composite structure. Our proposed model not only provides a possibility to stimulate and control electric and magnetic Fano resonances simultaneously for microwaves, but also holds great potential for biosensing and switching applications for even higher frequency range such as terahertz or optical region.

Breaking the symmetry to manipulate the magnetic Fano resonance in double split ring/square ring structure

Optical properties of the Double Split Ring/Square Ring nanostructurre are investigated by using finite element method. Electric and magnetic resonances at optical frequency can be induced by this nanostructure. The symmetry of the structure is broken by adjusting the arm length of the double split ring and the offsets of the square ring, which leads the changing of inductance and capacitance. New magnetic resonances can be achieved and enhanced. Fano resonances are produced by the overlapping interference between bright electric mode and dark magnetic mode. The nanostructure allows the generation of multiple magnetic Fano resonances and strong magnetic field enhancement, which has potential applications in plasmons propagation with low-loss magnetic and multi-wavelength surface enhanced spectroscopy.

Magnetic Fano resonance in silicon concentric nanoring resonator dimers under azimuthally polarized beam excitation

Abstract In this work, we proposed an all-dielectric nanostructure composed of silicon concentric nanoring resonator dimers (Si CNRD). We studied the scattering properties of Si CNRD and demonstrated the magnetic Fano resonance resulting from the interference between a narrow magnetic dipole mode and a broad magnetic dipole mode coupled into Si CNRD excited by an azimuthally polarized beam (APB). The spectral characteristics of the magnetic Fano resonance are characterized quantitatively by a coupled oscillator model. By changing the geometric parameters of the Si CNRD, the wavelength and intensity of the magnetic Fano resonance can be effectively adjusted. The nanostructure we proposed exhibits potential applications in low-loss sensors, nonlinearity, and laser devices.

Mixed Electric/Magnetic Fano Resonances in a Combined Square-Shaped Split Ring With an Internal Square Nanoantenna Nanocavities

Generally, the plasmonic Fano resonances can be divided into two types: the electric and the magnetic Fano resonance. Compared to pure electric or magnetic multiple Fano resonances, the mixed electric/magnetic multiple Fano resonances provide more flexibility for their application in multiwavelength surface enhanced Raman scattering and biosensing. Whereas, the dramatic difference between the two Fano resonances makes it difficult to realize magnetic and electric Fano resonances together in the same structure. In this paper, magnetic-octupole mode based Fano resonance and electric-quadrupole mode based Fano resonances in optical frequency were together achieved in a combined square-shaped split-ring resonator with an internal square nanoantenna nanocavities. The two Fano resonances are switchable by adjusting the polarization of the incident light. The lineshape modulated by the geometry and the environment of the two Fano resonances was investigated. Both the Fano resonances show high sensitivity to the environment. This study reveals a new multiple Fano resonance constitution and the proposed structure, which are expected with benefit application in multiwavelength polarization modulated chemistry and biological sensing.

Manipulation of multiple magnetic Fano resonances in nonconcentric asymmetric ring-ring nanostructure

Surface plasmon resonances (SPRs) of the nonconcentric asymmetric ring-ring nanostructure have been researched by using finite element method. In this plasmonic system, higher order magnetic Fano resonances are achieved. It is demonstrated that the magnetic Fano resonances originate from the coupling between the bright electric and the dark magnetic modes. The electric and magnetic resonances can be adjusted by the offset of the cavity, the width of the outer ring, the magnification times of the structure and the offset of the inner ring. The nanostructure allows the generation of multiple magnetic Fano resonances and strong magnetic field enhancement which can make the proposed nanostructure highly suitable for the plasmons propagation with low-loss magnetic, multi-wavelength surface enhanced spectroscopy and Fano switch.

Magnetic Fano resonance of heterodimer nanostructure by azimuthally polarized excitation.

The optical properties of a Si-Au heterodimer nanostructure, which is composed of an Au split nanoring surrounded by a Si nanoring with a larger diameter, are investigated both theoretically and numerically. It is found that a pure magnetic plasmon Fano resonance can be achieved in the Si-Au heterodimer nanostructure when it is excited by an azimuthally polarized beam. It is revealed that the pure magnetic Fano resonance is generated by the destructive interference between the magnetic dipole resonance of the Si nanoring and the magnetic dipole resonance of the Au split nanoring. A coupled oscillator model is employed to analyze the Fano resonance of the Si-Au heterodimer nanostructure. The pure magnetic response of the Si-Au heterodimer nanostructure is verified by the current density distributions and the scattering powers of the electric and magnetic multipoles. The Fano resonance in the Si-Au heterodimer nanostructure exhibits potential applications of low-loss magnetic plasmon resonance in the construction of artificial magnetic metamaterials.

Toroidal and magnetic Fano resonances in planar THz metamaterials

The toroidal dipole moment, a localized electromagnetic excitation of torus magnetic fields, has been observed experimentally in metamaterials. However, the metamaterial based toroidal moment was restricted at higher frequencies by the complex three-dimensional structure. Recently, it has been shown that toroidal moment could also be excited in a planar metamaterial structure. Here, we use asymmetric Fano resonators to illustrate theoretically and experimentally the underlying physics of the toroidal coupling in an array of planar metamaterials. It is observed that the anti-parallel magnetic moment configuration shows toroidal excitation with higher quality (Q) factor Fano resonance, while the parallel magnetic moment shows relatively lower Q factor resonance. Moreover, the electric and toroidal dipole interferes destructively to give rise to an anapole excitation. The magnetic dipole-dipole interaction is employed to understand the differences between the toroidal and magnetic Fano resonances. We further study the impact of intra unit-cell coupling between the Fano resonator pairs in the mirrored and non-mirrored arrangements. The numerical and theoretical approach for modelling the near-field effects and experimental demonstration of toroidal and magnetic Fano resonances in planar systems are particularly promising for tailoring the loss in metamaterials across a broad range of the electromagnetic spectrum.

Fine-Tuning of the Magnetic Fano Resonance in Hybrid Oligomers via fs-Laser-Induced Reshaping

Various clusters of metallic or dielectric nanoparticles can exhibit sharp Fano resonances originating from at least two modes interference of different spectral width. However, for practical applications such as biosensing or nonlinear nanophotonics, the fine-tuning of the Fano resonances is generally required. Here, we propose and demonstrate a novel type of hybrid oligomers consisting of asymmetric metal-dielectric (Au/Si) nanoparticles with a sharp Fano resonance in the visible range, which has a predominantly magnetic origin. We demonstrate both numerically and experimentally that such hybrid nanoparticle oligomers allow fine-tuning of the Fano resonance via fs-laser-induced melting of Au nanoparticles at the nanometer scale. We show that the Fano resonance wavelength can be changed by fs-laser reshaping very precisely (within 15 nm) being accompanied by a reconfiguration of its profile.

Magnetic Fano resonances by design in symmetry broken THz meta-foils

Magnetic Fano resonances in there-dimensional symmetry broken meta-foils at THz frequencies are theoretically and experimentally studied. Sharp Fano resonances occur due to the interference between different resonances and can be designed by choosing geometric parameters of the meta-foil. At the Fano resonances, the meta-foil supports antisymmetric modes, whereas, at the main resonance, only a symmetric mode exists. The meta-foil is left-handed at the Fano resonances and shows sharp peaks of the real part of the refractive index in transmission with small effective losses opening a way to very sensitive high-speed sensing of dielectric changes in the surrounding media and of mechanical configuration.