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Fano-like resonance in large-area magnetic metamaterials fabricated by nanoimprint technique title
摘要： We experimentally and theoretically investigated the Fano-like resonance in large-area magnetic metasurfaces fabricated by nanoimprint lithography technique based on elaborately designed Ag-SiN-Ag configuration. Asymmetric line shape is revealed in reflection spectrum of the magnetic metamaterials. The physical mechanism is elucidated through dispersion relation and electromagnetic field distribution analysis. Both the measured and calculated dispersion relation tell that there are magnetic resonance modes and surface lattices modes coexisting in the magnetic metamaterials, their coupling leads to the asymmetric profile in the reflection spectrum. The calculated electromagnetic field distribution further consolidate the coupling phenomenon in the magnetic metamaterials. This work might significantly prompt the applications of metamaterials in sensing, lasing, and optical devices designing.
关键词： SPP,magnetic resonance,Fano Resonance,surface lattice resonance,magnetic metamaterials
更新于2025-09-23 15:23:52
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Bound states in the continuum in the double-period rectangular hole arrays perforated in one layer of photonic crystal slab in the visible wavelength region
摘要： We investigate optical bound states in the continuum (BICs) supported by a photonic crystal (PhC) slab penetrated with two periodic rectangular hole arrays embedded each other parallelly and vertically. It proves that the tunable off-Γ BICs can be found in the structure of both types, but the at-Γ BICs can only be obtained in the parallel structure. Quality factors (Q-factor) are obtained extremely high exceeding 105 for both types of structures. The tunable off-Γ BICs can be modulated by the structure parameters. Especially, the sensitivity of the resonant wavelength on the surrounding medium refractive index change is very large for the structure in both types, and tunable off-Γ BICs can be tuned by varying the environmental index. The results above accord well from the finite difference time domain method (FDTD) and the temporal coupled mode theory (CMT), which are beneficial to design practical resonance elements based on optical BICs in various new optical applications.
关键词： Double-periodic rectangular hole arrays,Photonic crystal,Fano resonance,Bound state in the continuum
更新于2025-09-23 15:23:52
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Lightweight Ultra-Wideband RCS Reduction Structure using Double-Layer Metasurfaces
摘要： In this paper, we propose the design of a lightweight RCS reduction structure using double-layer metasurfaces. The structure is composed of two layers of metasurfaces spaced by PMI foams. To extend the bandwidth, two unit structures are firstly designed to operating in two respective bands for circularly polarized (CP) waves, which are then combined to act as the unit structure of the double-layer metasurface. The metasurface is expected to operate in two continuous bands. Nevertheless, due to the couplings between the two unit structures, there is Fano resonance that prohibits merging of the two bands. To solve this problem, we tune the resonant frequency of the bottom unit structure to suppress the Fano resonance and obtain a merged band. The combined unit structure is employed as the element of chessboard configuration, which can reduce RCS by more than 10dB in an ultra-wideband (4.5-16.5GHz). We designed, fabricated and measured a lightweight prototype (the aerial density is 726g/m2). Both the simulation and experiment result verify the design. This work provides an effective method of extending the operation band of RCS reduction without sacrificing the efficiency.
关键词： metasurface,ultra-wideband,Fano resonance,RCS reduction
更新于2025-09-23 15:22:29
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Fano Resonance on Nanostructured Lithium Niobate for Highly Efficient and Tunable Second Harmonic Generation
摘要： Second harmonic generation (SHG) is an important nonlinear process which is critical for applications, such as optical integrated circuit, nonlinear microscopy, laser, etc. Many challenges remain in the improvement of nonlinear conversion ef?ciency, since the typical value is of only 10?5 in nanostructures. Here, we theoretically demonstrate a periodic structure consisting of a lithium niobate (LN) bar and an LN disk, on a nanoscale (~300 nm) thin-?lm platform, which is proposed for a highly ef?cient SHG. By breaking the structure symmetry, a Fano resonance with a high Q, up to 2350 and a strong optical ?eld enhancement reaching forty-two folds is achieved, which yields a high conversion ef?ciency, up to 3.165 × 10?4. In addition to its strong second harmonic (SH) signal, we also demonstrate that by applying only 0.444 V on the planar electrode con?gurations of the nanostructured LN, the wavelength of SH can be tuned within a 1 nm range, while keeping its relatively high conversion ef?ciency. The proposed structure with the high nonlinear conversion ef?ciency can be potentially applied for a single-molecule ?uorescence imaging, high-resolution nonlinear microscopy and active compact optical device.
关键词： harmonic generation and mixing,lithium niobate,Fano resonance
更新于2025-09-23 15:22:29
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Actively tunable mid-infrared Fano resonance in Ge2Sb2Te5-based grating structures
摘要： Dynamic tuning of the resonance wavelength of subwavelength gratings in the mid-infrared (MIR) region via the permittivity change of phase-change material (PCM) has been demonstrated. A large shift in the peak of reflectance can be obtained by intermediate phase states of the Ge2Sb2Te5 (GST) layer. Fano resonance (FR) can be excited and is verified by the rigorous coupled-wave analysis (RCWA) method. Non-volatile tuning of lattice resonances over a range Δλ of about 1.9 μm (10.9 μm–12.8 μm) is achieved. Significant spectral tuning of FR can also be achieved by changing geometrical parameters as well as the angle of incidence. The wide range of the tunable FR in the technologically important MIR region offers a high resolution filter, which is useful for numerous sensing, imaging, and detection applications.
关键词： Fano resonance,Phase change materials,Mid-infrared
更新于2025-09-23 15:22:29
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Study of Fano Resonance in the Core-Level Absorption Spectrum in Terms of Complex Spectral Analysis
摘要： We study theoretically the core absorption spectrum of an impurity embedded in a tight-binding chain in terms of complex spectral analysis. The absorption spectral pro?le associated with the resonance states in principle exhibits an asymmetric Fano-type structure, even without apparent multiple interference transition paths. The asymmetric Fano absorption pro?le is attributed to the complex-valued oscillator strength of the transition to the resonance state belonging to the extended Hilbert space. The boundary condition on the continuum causes a large energy dependence of the self-energy, so that it enhances the nonlinearity of the eigenvalue problem of the effective Hamiltonian, yielding several non-analytic resonance states. The optical transitions to these resonance states constitute the overall absorption spectrum structure.
关键词： Fano resonance,core-level absorption spectrum,complex spectral analysis,extended Hilbert space,resonance states
更新于2025-09-23 15:21:21
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Controlling Fano resonances in multilayer dielectric gratings towards optical bistable devices
摘要： The spectral properties of Fano resonance generated in multilayer dielectric gratings (MDGs) are reported and numerically investigated in this paper. We examine the MDG consisting of numerous identically alternative chalcogenide glass (As2S3) and silica (SiO2) multilayers with several grating widths inscribed through the structure, emphasizing quality (Q) and asymmetric (q) factors. Manipulation of Fano lineshape and its linear characteristics can be achieved by tailoring the layers’ amount and grating widths so that the proposed structure can be applicable for several optical applications. Moreover, we demonstrate the switching/bistability behaviors of the MDG at Fano resonance which provide a significant switching intensity reduction compared to the established Lorentzian resonant structures.
关键词： Fano resonance,silica,optical bistable devices,chalcogenide glass,multilayer dielectric gratings
更新于2025-09-23 15:21:21
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Light-Tunable Fano Resonance in Metal-Dielectric Multilayer Structures
摘要： Recent progress on Fano resonances exhibited by metal-dielectric multilayer structures is reviewed. The Fano resonance in the multilayer structures is caused by coupling between a surface plasmon polariton mode supported by a metal-dielectric interface and a waveguide mode supported by a system of three dielectric layers. Electromagnetic calculations of attenuated total reflection spectra demonstrate the feasibility of realizing the Fano resonance, and the predicted Fano resonance was indeed observed experimentally. Since the structure is simple, it is easy to add the photofunctionality to the structure. Incorporation of photofunctional dye molecules into the waveguide layer made it possible to tune the Fano resonance by light irradiation.
关键词： Fano resonance,light tuning,surface plasmon polariton,waveguide mode,metal-dielectric multilayer structures
更新于2025-09-23 15:21:21
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Fano-resonant Excitations of Generalized Optical Spin Waves
摘要： While chiral materials possess spin-form wave functions as their eigenmodes, optical spin excitations cannot be obtained solely in chiral materials due to a lack of spin impedances. To date, spin excitation has generally been induced through non-conservative methods, such as circular dichroism or magneto-optical effects. In this chapter, we describe a conservative approach to optical spin excitation and control based on the spin-dependent appearance of Fano resonance. Starting from the development of the spin-form temporal coupled mode theory for 2D and 3D chiral resonances, the origin of the spin-Fano interactions is demonstrated in terms of the link between the spin eigenmodes in the polarization domain and anti-symmetric Fano resonances in the spectral domain. By comparing this spin-dependent Fano-resonant system with other optical spin materials, such as chiral, circular dichroic, and birefringent media, we discuss the impact of our results toward the realization of optical spintronics, such as applications of highly selective spin switching and unpolarized spinning operations.
关键词： Fano resonance,chiral materials,temporal coupled mode theory,optical spin,spintronics
更新于2025-09-23 15:21:21
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Fano Resonances in Light Scattering by Finite Obstacles
摘要： Light scattering by ?nite obstacles, either a single particle or a number of particles in arbitrary con?guration, exhibits various resonant effects. It turns out that almost any resonant response, either in directional or total light scattering, can be ef?ciently described in terms of Fano resonance. One of the peculiar features of the Fano resonance is complete destructive interference, which can be associated with radiationless excitations, such as nontrivial anapole modes.
关键词： Fano resonance,finite obstacles,light scattering,anapole modes
更新于2025-09-23 15:21:21