Interaction of magnetic resonators studied by the magnetic field enhancement

Sub wavelength all-dielectric structures processing simultaneously electric and magnetic resonances provide a new horizon for tailoring magnetic light–matter interaction that is often overlooked in optical spectrum. In general, the magnetic field enhancement can be boosted by utilizing the magnetic resonances of dielectric resonators where structural disorder effect is considered as a parasitic negative effect for the targeted response. Here, in contrast, we theoretically propose and experimentally demonstrate that compact disordered dielectric resonators with substantial enhancement of free-space magnetic field can be automatically designed by the combination of simulated annealing algorithm and numerical solution of Maxwell’s equations, providing an alternative for tailoring magnetic light–matter interaction. The functionality and reliability of the proposed concept are further verified by microwave experiment. Our results might facilitate the application of compact disordered magnetic resonators in enhancing magnetic dipole transition of quantum emitter, magnetic resonance imaging, wireless power transfer and beyond.

A certain value, a method to analyze bending sensing rules of long-period fiber grating (LPFG) according to bending curvature, grating length and grating period was reported, based on coupled-mode theory and perturbation approximation. The transmission spectra of the bended LPFG split when the bending curvature reaches a certain value. The two resonant wavelengths of the splitting peaks change conically with the bending curvature and inversely with grating period, but are independent on grating length. The LPFG written on the B-Ge co-doping single-mode fiber proves the above conclusion. The two resonant wavelengths of the splitting peaks change conically with the bending curvature consist of fiber grating strain sensor. It has following characteristic. Firstly, resonant wavelength transforms into the frequency shift through the electro-optical heterodyne, may cause the ordinary optics wave length survey to transform as the electricity frequency survey, improve the detection and resolution gain five or more orders of magnitude. Secondly, the two split resonant peak wavelength difference frequency is possible to obtain the higher examination sensitivity. Thirdly, use the differential motion structure to eliminate the environment disturbance. Fourthly, transmission peak sensor is suitable to consist of the small array sensor. After a resonant wavelength heterodyne photoelectric conversion for the frequency change, can make an ordinary optical wavelength into electricity to detect the frequency of detection, so that detection and resolution gain through more than five orders of magnitude. 2, the two split resonant peak wavelength difference frequency of changes in detection sensitivity can be higher. 3 Differential structure suitable for the elimination of environmental interference. 4 transmission peaks constitute a sensor suitable for small size of the sensor array. The above characteristic is suitable to constitute the new optical fiber array hydrophone. Many long period fiber grating through elastic carrier curving in appropriate fixed angle, after the seal, uses as the optical fiber hydrophone array. Array works not only in space division multiplexing way, but also work in the wavelength division multiplying and the multiplying active status. The different bending strain may cause the fiber grating bias at the different wave length, can use the optical fiber phase-shift diffraction grating separate the wave length. Detector's connection optical fiber length to different sensor is different, therefore the signal arrives at different time, is advantageous to the multiplying time sampling. The use of photoelectric heterodyne method of long-period gratings on the transmission spectrum of detection not only has high sensitivity but also eliminates polarization effects Two split peaks due to resonant wavelength changes with the bending curvature of the relationship was quadratic curve relationship, the use of photoelectric heterodyne detection frequency, the frequency range up to 1012Hz, the frequency resolution of 10Hz. By LPFG right, photovoltaic devices and microwave heterodyne frequency meter combination can solve the interferometric fiber-optic hydrophone polarization effects and the problem of inadequate resolution, consisting of long-period grating fiber-optic hydrophone size is very small, very convenient to install. In addition the use of long-period fiber grating (LPFG), can constitute an earthquake, bridge monitoring, fatigue testing of aircraft and other important sensor, with wide applications.

In this article, we introduce a new optical energy focusing structure consisting of a circular dielectric Bragg nanocavity and a circular metallic plasmonic lens. Via the hybridization of Bragg cavity modes and surface plasmon modes, optical energy is highly confined in the central region of the Bragg nanocavity under linearly polarized illumination. When either a bowtie nano-antenna (BNA) or a magnetic resonator (MR) is placed on this focusing structure, the energy can be high-efficiently coupled and focused into the BNA or MR. Simulations show that the electric field enhancement (|E|/|E0|) in the BNA and magnetic field enhancement (|H|/|H0|) in the MR can be more than 3000 and 200, respectively. This proposed hybrid dielectric-metallic structure opens a new avenue in energy focusing and transferring and provides opportunities for various applications, including single-molecule SERS, optical trapping, photolithography, fluorescent microscopy, magnetic sensors, etc.

Geometrical optimization study of diabolo nanoantenna

In magnetic resonance experiments, it is widely recognized that a nonuniform magnetic field can lead to an increase in the resonance line width, as well as a reduction in sensitivity and spectral resolution. However, a nonuniform magnetic field can also cause shifts in resonance frequency, which has received far less attention. In this work, we investigate the frequency shift caused by boundary relaxation and nonuniform magnetic field with arbitrary spatial distribution. We find that this frequency shift is spin-species dependent, implying a systematic error in NMR gyroscopes and comagnetometers. The first order correction to this systematic error is proportional to the difference of boundary relaxation rate, and dominates for small cells. In contrast, the third and higher order corrections arise from the difference of gyromagnetic ratios of spin species, and dominates for large cells. This insight helps understanding the unexplained isotope shifts in recent NMR gyroscopes and new physics searching experiments that utilize comagnetometers. Finally, we propose a tool for wall interaction research based on the frequency shift’s dependency on boundary relaxation.

We investigated theoretically and numerically the optical pulling and pushing forces acting on silicon (Si) nanospheres (NSs) with strong coherent interaction between electric and magnetic resonances. We examined the optical pulling and pushing forces exerted on Si NSs by two interfering waves and revealed the underlying physical mechanism from the viewpoint of electric- and magnetic-dipole manipulation. As compared with a polystyrene (PS) NS, it was found that the optical pulling force for a Si NS with the same size is enlarged by nearly two orders of magnitude. In addition to the optical pulling force appearing at the long-wavelength side of the magnetic dipole resonance, very large optical pushing force is observed at the magnetic quadrupole resonance. The correlation between the optical pulling/pushing force and the directional scattering characterized by the ratio of the forward to backward scattering was revealed. More interestingly, it was found that the high-order electric and magnetic resonances in large Si NSs play an important role in producing optical pulling force which can be generated by not only s-polarized wave but also p-polarized one. Our finding indicates that the strong coherent interaction between the electric and magnetic resonances existing in nanoparticles with large refractive indices can be exploited to manipulate the optical force acting on them and the correlation between the optical force and the directional scattering can be used as guidance. The engineering and manipulation of optical forces will find potential applications in the trapping, transport and sorting of nanoparticles.

Using perturbation theory, expressions are derived for the frequency shift of a circularly polarized resonant microwave cavity upon insertion of a ferrite sample small compared with the wavelength. Retardation effects are considered in deriving the rf field h2 internal to the sample. By integrating h1·h2dv (where h1 is the applied rf field) over the sample volume, a closed-form expression is obtained for the cavity frequency shift. The theory is applied to the magnetic resonance in ferrites. The calculated magnetic resonance line shape is found to remain symmetrical as the sample size is increased. Retardation effect, thus, does not explain the asymmetry of the resonance lines which have been observed for polycrystalline ferrite. Results of the theory are also compared with measurements on a single crystal of ferrite having the rather large maximum permeability loss term of 100. Theoretical and measured values are in close agreement. The theory is also compared with the somewhat different results of other recent theoretical treatments, in which an approximate expression for an effective magnetic dipole moment for the sample was computed, rather than integrating the internal rf fields over the volume of the sample.

In this study, finite element modelling (FEM) is used to estimate the stresses induced by the package on a high precision silicon resonator. A link between the induced stresses and strains at different temperatures and the shift in the resonance frequency is presented. In order to accentuate the effects of the package on the resonance frequency of the resonators a double clamped beam vibrating in a flexural mode was designed. The resonance frequency can be shifted dramatically by the mechanical stress induced by the package; however, those stresses can be used to compensate the shift in resonance frequency due to the intrinsic temperature dependence of silicon. In order to prove the package design, a full 3D FEM of a O-level package containing a square Lame mode resonator is studied. Modelling results show that this resonator and package design is almost insensitive to the package deformation.

Bioelectronic sensors using magnetic resonance (MR) show great promise for real-time cardiovascular health monitoring, enabling both sensing and wireless powering. However, shifts in resonant frequency due to physiological variations can compromise Wireless Power Transfer (WPT) efficiency. This paper uses a circuit model approach to investigate the trade-off between sensing and WPT performance and defines key performance parameters and optimal conditions for both functions. Then, this mathematical framework is applied to model an arterial pressure monitoring case study, and the results are compared against experimental data, providing insights and design guidelines to optimize sensitivity and WPT efficiency in long-term implantable devices.

The first successful nuclear magnetic resonance (NMR) experiments in bulk matter were carried out by Bloch and his collaborators at Stanford and by Purcell and his collaborators at Harvard, and were published in 1946. In the 38 yr since those first papers, NMR techniques have been widely applied in many areas of physics, chemistry, biochemistry, and biology. These applications are based almost entirely on the fact that the quantized energy levels available in a magnetic field to a nucleus with spin angular momentum and a magnetic moment are separated by an energy that is proportional to the strength of the magnetic field at the nucleus. This field is always slightly different from an applied extermal magnetic field because of perturbations by the nearby electrons and magnetic nuclei and by local and long-range magnetic susceptibility effects. These small differences result in shifts in the resonance frequency. Also, the fluctuations in the magnetic field at the nucleus caused by its motions and those of nearby nuclei and impaired electrons determine the transition rates between the nuclear Zeeman energy levels and the rates at which phase coherence of the detectable component of the nuclear magnetization are lost. Such changes in the relaxation times are useful because of their sensitivities to molecular motions and local environments.KeywordsNuclear Magnetic ResonanceNuclear Magnetic Resonance SignalNuclear Magnetic Resonance ExperimentNuclear Magnetic Resonance TechniqueSpin Angular MomentumThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The detection of branded and unbranded chemical materials is essential for the quality control assessment. In this work, a metamaterial inspired sensor is designed and fabricated, which incorporates oval-shaped wing resonators, in order to use to detect branded and unbranded diesels in the X-band frequency region. The simulation studies were carried out by using the Computer Simulation Technology (CST) Microwave studio. A transmission line was introduced into the sensor design and genetic algorithm was used to optimize the proposed structure. Parametric study was investigated by changing the permittivity, permeability of the sensor layer, width of the transmission line, materials of the substrate layer, and width of the resonator. Results showed that different factors can be considered to sense the chemical materials including the shift in resonant frequency and amplitude variation in the reflection or transmission spectrum. It was found that the sensible variation in the transmission value is about −3.2 dB, which is superior to that reported in literature. It was concluded that the sensor is highly sensitive to distinguish the branded diesel from the unbranded one, which makes it viable for detecting fluidics in the chemical industry and medicine.

On natural frequencies of three-dimensional moonpool of vessels in the fixed and free-floating conditions

Experimental investigation on the effect of concentration on the resonance frequency of lipid coated ultrasonically excited microbubbles

We devised a signal-switching mechanism (SSM) based on the transportation of liquid metal droplets (LMDs). This method transmits power selectively to the light-emitting diode (LED) connected with a pair of electrodes, including a transported LMD. When an LMD is transported through a channel between multiple pairs of electrodes, the capacitance of the pair of electrodes decreases. In the SSM, we connected the electrodes with a coil and LEDs and investigated the frequency response of the impedance of the mechanism. As a result, we find the resonant phenomena of the SSM and the shift of the resonant frequency owing to the transportation of the LMD. By applying an alternating voltage, whose frequency corresponded with that of the resonant frequency of the LED-connected SSM, we could selectively transmit power to the LED activated by an LMD. Our equivalent circuit model quantitatively predicts the transmitted power and the shift in the resonant frequency due to the transportation of LMDs. The SSM using LMDs has a promising potential to contribute to soft multiplexers without complex wiring, where they can help integrate not only multiple sensors but also actuators as well.

This paper explores the potential of phase change materials (PCM) for dynamically tuning the frequency response of a dumbbell u-slot defected ground structure (DGS)-based band stop filter. The DGSs are designed using co-planar waveguide (CPW) line structure on top of a barium strontium titanate (Ba0.6Sr0.4TiO3) (BST) thin film. BST film is used as the high-dielectric material for the planar DGS. Lower insertion loss of less than -2 dB below the lower cutoff frequency, and enhanced band-rejection with notch depth of -39.64 dB at 27.75 GHz is achieved by cascading two-unit cells, compared to -12.26 dB rejection with a single-unit cell using BST thin film only. Further tunability is achieved by using a germanium telluride (GeTe) PCM layer. The electrical properties of PCM can be reversibly altered by transitioning between amorphous and crystalline phases. We demonstrate that incorporating a PCM layer into a DGS device allows for significant tuning of the resonance frequency: a shift in resonance frequency from 30.75 GHz to 33 GHz with a frequency shift of 2.25 GHz is achieved, i.e., 7.32% tuning is shown with a single DGS cell. Furthermore, by cascading two DGS cells with PCM, an even wider tuning range is achievable: a shift in resonance frequency from 27 GHz to 30.25 GHz with a frequency shift of 3.25 GHz is achieved, i.e., 12.04% tuning is shown by cascading two DGS cells. The results are validated through simulations and measurements, showcasing excellent agreement.