Kinds Of Resonant Modes Research Articles

Independently tunable Fano resonances based on MDM configuration using a ring resonator with nanodots

A novel designed Fano system using metal-dielectric-metal (MDM) configuration is proposed and numerically evaluated via finite element method (FEM). At the same time, the formation mechanism of Fano resonance is explored based on numerical simulations. Moreover, the standing wave theory and the temporal coupled-mode theory (CMT) are utilized to investigate the resonant phenomenon. The system is constructed by the tooth cavity connected into straight waveguide and a circular ring resonator with nanodots (CRRN). The simulation results indicate that the CRRN supports the two kinds of resonant modes: TM2 and like-TM2 mode, whose distribution of field patterns (the resonant point related to like-TM2 mode) can be flexibly controlled by the position of nanodot (the number and thickness of the nanodots). With regard to the excited dual Fano resonances, their emergence or disappearance can be tuned by nanodot position, and the independent tunability of FR2 can be realized by adjusting nanodot’s number and thickness. In addition, the Fano system with a sensing performance of 942 nm RIU−1 has been demonstrated, which can be great promising for detecting glucose concentration. In summary, the proposed Fano structure may provide a feasible scheme to flexibly manipulate the dual Fano resonances and detect glucose concentration.

Vector magnetic field measurement based on magnetic fluid and high-order cladding-mode Bragg grating

An optical fiber-based vector magnetic field sensor combining fiber Bragg gratings (FBGs) and magnetic fluids (MFs) is proposed and experimentally demonstrated. The Bragg gratings are inscribed on the core and the cladding of a multi-clad fiber (MCF). Splicing the MCF with a standard single-mode fiber (SMF) via core mismatch provides a cladding-mode generation mechanism. Then, the high-order cladding mode is excited with the increasing off-axis distance. There are two kinds of resonant modes in the reflection spectrum of the sensor, which are the high-order cladding mode and the fundamental core mode. The intensity of the first mode shows an excellent response to the magnetic field intensity and the direction. The intensity sensitivity of the magnetic field sensor is −0.143 dB/Oe in a linear range of 60–110 Oe. Furthermore, the second mode intensity is quite stable and varies with the ambient temperature. Thus, the proposed magnetic field sensor can simultaneously measure the magnetic field and the temperature.

Electromagnetic-Power-Based Modal Classification, Modal Expansion, and Modal Decomposition for Perfect Electric Conductors

Traditionally, all working modes of a perfect electric conductor are classified into capacitive modes, resonant modes, and inductive modes, and the resonant modes are further classified into internal resonant modes and external resonant modes. In this paper, the capacitive modes are further classified into intrinsically capacitive modes and nonintrinsically capacitive modes; the resonant modes are alternatively classified into intrinsically resonant modes, which are further classified into nonradiative intrinsically resonant modes and radiative intrinsically resonant modes, and nonintrinsically resonant modes; the inductive modes are further classified into intrinsically inductive modes and nonintrinsically inductive modes. Based on the modal expansion corresponding to these new modal classifications, an alternative modal decomposition method is proposed. In addition, it is also proved that all intrinsically resonant modes and all nonradiative intrinsically resonant modes constitute linear spaces, respectively, but other kinds of resonant modes cannot constitute linear spaces; by including the mode 0 into the intrinsically capacitive mode set and the intrinsically inductive mode set, these two modal sets become linear spaces, respectively, but other kinds of capacitive modes and inductive modes cannot constitute linear spaces.

Surface-Plasmon-Polaritons-Assisted Enhanced Magnetic Response at Optical Frequencies in Metamaterials

We theoretically study the coupling of magnetic plasmon polaritons (MPPs) with propagating surface plasmon polaritons (SPPs) in a system composed of an array of metal nanowires close to a metal film with a dielectric spacer. Strong coupling between MPPs and SPPs is observed, manifested by the anticrossing behavior of the resonant positions in the reflection spectra. It creates narrow-band hybridized MPPs with Rabi-type splitting as large as 250 meV. Moreover, we also found that the coupling between the MPPs and the SPPs can be tailored by the period of the metal nanowire array to affect the magnetic response of the plasmonic structure. Above the resonant wavelength of the MPPs, coupling between two kinds of resonance modes can lead to a 20-fold enhancement of the magnetic fields in the dielectric spacer, as compared with the pure magnetic resonance upon the excitation of the hybridized MPPs, whereas below it, coupling cannot lead to a magnetic field enhancement. We suggest that this feature could offer a feasible way to achieve huge magnetic field enhancement at optical frequencies and hold promising potential applications in magnetic nonlinearity and sensors.

Enhanced THz resonance based on the coupling between Fabry–Perot oscillation and dipolar-like resonance in a metamaterial surface cavity

We presented an enhanced resonance with ultra-wide band in the terahertz (THz) regime in a THz metamaterial system composed of a pair of circular rings arrays which act as two opposite mirrors. The two opposite mirrors, both of which will induce a dipolar-like resonance under the incident wave, together with the gap between them will constitute a Fabry–Perot cavity which contributes to a Fabry–Perot oscillation in the system. These two kinds of resonant modes, the dipolar-like resonance and Fabry–Perot oscillation, can be coupled with each other in an optimized structure, which leads to an enhanced electromagnetic resonance. From the experimental results, it can be found that such coupling leads to a nearly zero transmission zone with 0.12 THz bandwidth which is much better than individual conventional metamaterial system. This coupling mechanism could provide a new way for the realization of strong resonance, which shows great potential for THz pass-band or stop-band filters, THz resonators, THz absorbers, frequency selective devices and so on.

Superconductivity from a non-Fermi-liquid metal: Kondo fluctuation mechanism in slave-fermion theory

We find new mechanism of superconductivity beyond the spin-fluctuation theory, the standard model for unconventional superconductivity in the weak coupling approach, where Kondo fluctuations result in multi-gap superconductivity around an antiferromagnetic quantum critical point of the slave-fermion theory. Fingerprints of the hybridization mechanism are two kinds of resonance modes in not only spin but also charge fluctuations, originating from $d-wave$ pairing of conduction electrons and spinless holons, respectively, thus differentiated from the spin-fluctuation mechanism. We show that the ratio between each superconducting gap for conduction electrons $\Delta_{c}$ and holons $\Delta_{f}$ and the transition temperature $T_{c}$ is $2\Delta_{c} / T_{c} \sim 9$ and $2\Delta_{f} / T_{c} \sim \mathcal{O}(10^{-1})$, remarkably consistent with $CeCoIn_{5}$.

Analysis of planar defect structures in three-dimensional layer-by-layer photonic crystals

The properties of planar defect structures, which are created by changing the dielectric distribution at the central layer of a three-dimensional (3D) layer-by-layer photonic crystal, are theoretically investigated by utilizing a parallel 3D finite-difference time-domain method and the plane-wave expansion method. Two different kinds of resonant modes, the defect mode and the band-edge resonant mode, have been clarified by spectrum analysis and calculated mode profiles. It is shown that the resonant modes can be controlled by changing the periodicity, the thickness, or the dielectric constant of materials at the defect layer. Besides, photonic band edges can be shifted by applying dislocation to a layer of dielectric rods.

Well‐posedness of integral equations for modeling electromagnetic scattering from cavities

Integral equations for modeling electromagnetic scattering from indented screens or cavity structures are proposed using a symmetric equivalent current model, which is based on image theory with a perfect electrically conducting (PEC) ground plane. The well posedness of the proposed integral equations is theoretically established in this paper. It is known that all resonance modes for cavity problems either due to the presence of a perfect magnetically conducting (PMC) open aperture or a PEC open aperture. In this paper, it is proved that both kinds of resonance modes cannot exist for the proposed integral equations without excitation. To numerically examine this well posedness, the condition numbers of resultant matrices from the generalized network formulation and proposed integral equations are analyzed as functions of frequency and the depth of cavity. The numerical analysis of the condition numbers obtained also shows that the integral equations proposed in this paper are immune to the problem of the interior resonance for three‐dimensional cavity problems. Moreover, simulation of scattering from standard cavity structures verifies the validity of the proposed integral equations.

Higher-order resonant modes in a photonic heterostructure nanocavity

We investigated the optical characteristics of higher-order resonant modes for a heterostructure nanocavity formed in a two-dimensional photonic-crystal silicon slab. Two kinds of resonant modes were observed, the nanocavity modes and the Fabry–Pérot modes. High quality factors of more than 1.0×106 were obtained not only for the nanocavity mode but also for the Fabry–Pérot modes.

RADIATION PATTERN MEASUREMENTS ON A MILLIMETER-WAVE OPEN RESONATOR

Far-field radiation patterns can be used for identifying different kinds of resonant modes in a gyrotron cylindrical open resonator. The operating TE021 mode is identified among its closest competitors TE221 and TE611 by measuring radiation patterns obtained experimentally based on millimeter wave source for exciting the open resonator. A good agreement between experimental and, theoretically predicted values was found.

Planar sub-wavelength cavity resonator containing a bilayer of anisotropic metamaterials

We have studied the resonant modes in a planar cavity resonator containing a bilayer of non-dissipative anisotropic metamaterials. Different from the isotropic case, the resonance in such a resonator is closely related to the dispersion relation of the anisotropic medium. Three cases of different combinations of materials are discussed and it is found that sub-wavelength resonant modes may occur in all cases. Three kinds of resonant modes with different electromagnetic field distributions have been revealed and analysed. Requirements of the material and geometry parameters to construct a sub-wavelength resonator are revealed by an approximate analysis and verified by a rigorous solution of the characteristic equation, which demonstrate that this kind of sub-wavelength resonator brings more design flexibility and tolerance.

Local resonant characteristics of a layered cylinder embedded in the elastic medium

Three kinds of resonant modes of a single layered circular elastic cylinder embedded in the elastic medium are analysed by considering the oscillation of the scatter's core, based on the fact that the core moves as a rigid body when the shell material is very compliant. The resonant frequencies of the single resonator acquired by our method are in good agreement with those calculated by the local interaction simulation approach (LISA) for the local resonant phononic crystal. Therefore, the local resonant characteristics of a single layered circular elastic cylinder can be used to evaluate the resonant frequencies of the phononic crystal. The effects of the geometrical and physical parameters of the shell and the core are also studied in details. This work is significant for designing the locally resonant phononic crystal based on the local resonant characteristics of the single resonator and the resonant frequencies can be tuned by selecting the geometrical sizes and the materials.

Two phase collective modes in a Josephson vortex lattice in the intrinsic Josephson junctionBi2Sr2CaCu2O8+δ

Josephson plasma excitations in the high $T_c$ superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ have been investigated in a wide microwave frequency region (9.8 -- 75 GHz), in particular, in magnetic field applied parallel to the $ab$ plane of the single crystal. In sharp contrast to the case for magnetic fields parallel to the c axis or tilted from the $ab$ plane, it was found that there are two kinds of resonance modes, which are split in energy and possess two distinctly different magnetic field dependences. One always lies higher in energy than the other and has a shallow minimum at about 0.8 kOe, then increases linearly with magnetic field. On the other hand, another mode begins to appear only in a magnetic field (from a few kOe and higher) and has a weakly decreasing tendency with increasing magnetic field. By comparing with a recent theoretical model the higher energy mode can naturally be attributed to the Josephson plasma resonance mode propagating along the primitive reciprocal lattice vector of the Josephson vortex lattice, whereas the lower frequency mode is assigned to the novel phase collective mode of the Josephson vortex lattice, which has never been observed before.