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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || A Full-Retarded Spectral Technique for the Analysis of Fano Resonances in a Dielectric Nanosphere
摘要： We introduce a representation of the electromagnetic ?eld scattered by a homogeneous sphere in terms of a set of full-retarded modes independent of its permittivity. Within this framework, we introduce the orthogonality properties of the modes, their resonance conditions, and their classi?cation into narrow and broad modes. We also discuss the role played by the material properties in determining the resonant width of a given mode and in enabling or preventing the multimode interference. We use this theory to unveil the origin of Fano lineshapes in the scattering ef?ciency of a spherical nanoparticle, by identifying the interfering modes responsible for peaks and dips. Eventually, by using the introduced theoretical approach, we design the permittivity of a homogeneous sphere of size comparable to the incident wavelength to cancel its backscattering through directional multimode interference.
关键词： full-retarded modes,Fano resonances,electromagnetic scattering,permittivity design,dielectric nanosphere
更新于2025-09-23 15:21:21
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THEORETICAL AND EXPERIMENTAL INVESTIGATION OF FERRITE-LOADED WAVEGUIDE FOR FERRIMAGNETISM CHARACTERIZATION
摘要： This work proposes an approach to retrieve the ferrite’s electromagnetic properties in a single compact con?guration, simpler than the traditional measurement systems. The ferrite under test is fully inserted into a rectangular waveguide with a magnetic bias. The complex scattering parameters are theoretically analyzed under the consideration of modal e?ect at isotropy-anisotropy interfaces. Extraordinarily sharp Fano resonances are observed in the scattering spectrums, originating from the multimode interference inside the magnetized ferrite. There is good agreement among theoretical, experimental, and full-wave simulation results. This model can be further utilized to simultaneously retrieve all ferrite properties, including permittivity (ε), saturation magnetization (4πMs), and magnetic linewidth (ΔH) from the measured scattering parameters, facilitating the designs and applications of ferrite devices.
关键词： ferrite,scattering parameters,ferrimagnetism,Fano resonances,waveguide
更新于2025-09-23 15:21:01
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Plasmonic refractive index sensor with multi-channel Fano resonances based on MIM waveguides
摘要： A multi-channel Fano resonant structure is proposed and analyzed based on subwavelength metal–insulator–metal (MIM) waveguides. First, two MIM output ports associated with specific side-coupled cavities are designed to locate at the center and quarter positions of an end-coupled cavity, respectively. Since the interference between the dark and bright modes, dual-channel Fano resonances with asymmetrical lines shapes are obtained at both ports, respectively. High sensitivity and figure of merits are investigated. Besides, phase shifts are also investigated leading to positive and negative group delays available at the Fano peaks and dips, respectively. Likewise, two extra output ports with identical resonant cavities are placed on the other side of the end-coupled cavity. In this case, four-channel Fano resonances with considerable performances are obtained. The proposed structure is analyzed by the coupled mode theory and the finite difference time domain method. It is believed this device can be used as a chip-scale refractive index sensor and optical filter.
关键词： Fano resonances,subwavelength MIM waveguide,refractive index sensor.
更新于2025-09-23 15:21:01
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A nanosensor with ultra-high FOM based on tunable malleable multiple Fano resonances in a waveguide coupled isosceles triangular resonator
摘要： A simple plasmonic structure, which is made up of a metal baffle in the middle of the metal–insulator–metal (MIM) waveguide coupled with an isosceles triangular cavity, is reported to achieve triple Fano resonances. These Fano resonances are numerically calculated by the finite element method (FEM). Besides, the multimode interference coupled mode theory (MICMT) and the standing wave theory are used for analyzing the Fano resonances phenomenon. On the one hand, these three Fano resonances can be independently tuned by adjusting the structural parameters, which makes the design of highly integrated photonic circuits more flexible. On the other hand, the proposed structure is well malleable and can be easily extended to a quintuple Fano system by introducing a ring resonator. Furthermore, the suggested structure can act as a high efficient refractive index (RI) sensor, yielding a great sensitivity of 1200 nm/RIU and a ultra-high maximal figure of merit (FOM) value of 3.0 × 106. Comparing with other similar sensors, our structure has relatively good sensitivity and it is superior to other structures in the maximal FOM, which obviously demonstrates its excellent nano-sensing performance.
关键词： Multiple Fano resonances,Multimode interference coupled mode theory (MICMT),Refractive index (RI) sensor,Ultra-high FOM,Surface plasmon polaritons (SPPs)
更新于2025-09-23 15:21:01
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Unidirectional photonic circuit with a phase-change Fano resonator
摘要： We demonstrate that the integration of a phase-change material (PCM) in one of the two microresonators of a photonic circuit, coupled to a bus waveguide, can lead to unidirectional Fano resonances and to the emergence of a unidirectional transmission window. The phase change is caused by light-induced heating and is accompanied by an abrupt increase in the extinction coefficient of the PCM resonator. Due to the photonic circuit asymmetry, the critical value of the input light intensity triggering the phase change is strongly dependent on the input light direction. The latter determines the unidirectional nature of the emerging transmission window. This effect can be utilized in on-chip magnetic-free isolators and Q switches.
关键词： optical isolators,phase-change material,photonic circuit,unidirectional transmission,Fano resonances
更新于2025-09-23 15:21:01
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Weak Coupling, Strong Coupling, Critical Coupling and Fano Resonances: A Unifying Vision
摘要： The transversal concepts of weak, strong and critical coupling, and of Fano resonances, are analyzed within a unified framework which relies on a simple classical model of driven-dissipative coupled oscillators. A careful exploration of the system’s parameter space has led to the emergence of certain intriguing phenomena, which we named lineshape inheritance, universal absorption lineshape, and strong critical coupling. These concepts may be of relevance when attempting to understand the response of a diversity of systems, especially in the fields of (quantum) light-matter coupling, and of solid-state nanophysics, where the basic scheme of multi-oscillator dissipative resonances is often encountered.
关键词： strong coupling,Fano resonances,critical coupling,solid-state nanophysics,weak coupling,light-matter coupling
更新于2025-09-23 15:21:01
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Double Fano resonances in hybrid disk/rod artificial plasmonic molecules based on dipole-quadrupole coupling
摘要： Fano resonance can be achieved by the destructive interference between a superradiant bright mode and a subradiant dark mode. A variety of artificial plasmonic oligomers have been fabricated to generate Fano resonance for its extensive applications. However, the Fano resonance in plasmonic oligomer systems comes from the interaction of all metal particles, which greatly limits the tunability of the Fano resonance. Besides, only a single Fano resonance is supported by many existing plasmonic oligomers, while multiple Fano resonances mostly occur in complex and multilayer structures, whose fabrication is greatly challenging. Here, a simple asymmetric plasmonic molecule consisting of a central metal disk and two side-coupled parallel metal rods is demonstrated. The simulation and experimental results clearly show that double Fano resonances appear in the transmission spectrum. In addition, the two Fano peaks can be independently tuned and single/double Fano peak switching can be achieved by changing one rod length or the gap distances between the rods and the disk. The modulation method is simple and effective, which greatly increases the tunability of the structure. The proposed asymmetric artificial plasmonic molecule can have applications in multi-channel optical switches, filters and biosensors. Moreover, the controllable plasmonic field intensity in the gap between the disk and rods also provides a new control means for plasmon-induced photocatalytic reactions and biosynthesis.
关键词： plasmonic oligomers,biosynthesis,Fano resonance,filters,optical switches,biosensors,asymmetric plasmonic molecule,plasmon-induced photocatalytic reactions,double Fano resonances
更新于2025-09-23 15:19:57
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Nonlinear Optics in Dielectric Guided-Mode Resonant Structures and Resonant Metasurfaces
摘要： Nonlinear optics is an important area of photonics research for realizing active optical functionalities such as light emission, frequency conversion, and ultrafast optical switching for applications in optical communication, material processing, precision measurements, spectroscopic sensing and label-free biological imaging. An emerging topic in nonlinear optics research is to realize high efficiency optical functionalities in ultra-small, sub-wavelength length scale structures by leveraging interesting optical resonances in surface relief metasurfaces. Such artificial surfaces can be engineered to support high quality factor resonances for enhanced nonlinear optical interaction by leveraging interesting physical mechanisms. The aim of this review article is to give an overview of the emerging field of nonlinear optics in dielectric based sub-wavelength periodic structures to realize efficient harmonic generators, wavelength mixers, optical switches etc. Dielectric metasurfaces support the realization of high quality-factor resonances with electric field concentrated either inside or in the vicinity of the dielectric media, while at the same time operate at high optical intensities without damage. The periodic dielectric structures considered here are broadly classified into guided-mode resonant structures and resonant metasurfaces. The basic physical mechanisms behind guided-mode resonances, electromagnetically-induced transparency like resonances and bound-states in continuum resonances in periodic photonic structures are discussed. Various nonlinear optical processes studied in such structures with example implementations are also reviewed. Finally, some future directions of interest in terms of realizing large-area metasurfaces, techniques for enhancing the efficiency of the nonlinear processes, heterogenous integration, and extension to non-conventional wavelength ranges in the ultra-violet and infrared region are discussed.
关键词： harmonic generation,guided-mode resonance,four-wave mixing,Mie scattering,optical resonances,nonlinear optics,sub-wavelength gratings,Fano resonances,optical switching
更新于2025-09-23 15:19:57
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Self-Organized Nanorod Arrays for Large-Area Surface Enhanced Infrared Absorption
摘要： Highly sensitive Surface Enhanced Infrared Absorption (SEIRA) spectroscopy capabilities are demonstrated by exploiting large-area templates (cm2) based on self-organized (SO) nanorod antennas. We engineered highly dense arrays of gold nanorod antennas featuring polarization-sensitive localized plasmon resonances, tunable over a broadband near- and mid-infrared (IR) spectrum, in overlap with the so called ‘functional group’ window. We demonstrate polarization-sensitive SEIRA activity, homogenous over macroscopic areas and stable in time, by exploiting prototype self-assembled monolayers of IR-active octadecanthiol (ODT) molecules. The strong coupling between the plasmonic excitation and the molecular stretching modes give rise to characteristic Fano resonances in SEIRA. The SO engineering of the active hot-spots in the arrays allows to achieve signal amplitude improved up to the 5.7 %. This figure is competitive to the response of lithographic nanoantennas and is stable when the optical excitation spot varies from the micro- to the macroscale, thus enabling highly sensitive SEIRA spectroscopy on cost-effective nanosensor devices.
关键词： IR spectroscopy,large area nanosensors,Surface Enhanced Infra-Red Absorption (SEIRA),self-organized arrays,Fano resonances,Plasmonic nanoantennas
更新于2025-09-23 15:19:57
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Fanoa??Andreev and Fanoa??Majorana Correspondence in Quantum Dot Hybrid Structures
摘要： A correspondence on the single-electron transport properties between systems of different nature, a topological quantum system and a (conventional) non-topological one, is demonstrated. Specifically, the equivalence between the Fano resonances obtained in T-shaped double quantum dot system coupled to a superconducting lead (QD–QD–S) and a topological superconductor ring nanowire (QD–MBSs) is presented. The non-zero value of the Fano (anti)resonance in the conductance of the QD-MBSs systems is shown as a consequence of a complex Fano factor qM, which is equivalent to the complex Fano factor qS of the QD–QD–S. The complex nature of qS is understood as a sign of a phase introduced by the superconducting lead in the QD–QD–S. It is because of this phase that the correspondence between the QD–QD–S and the QD–MBSs is possible. It is believed that these results can help to reveal the importance of the Fano interference process toward the understanding of the role of the superconductor lead in the QD–QD–S system as well as giving a clear signature of the presence of MBS’s in the topological system.
关键词： Majorana bound states,proximity effects,Andreev reflection,(anti)fano resonances,topological superconductors
更新于2025-09-23 15:19:57