Disk Dielectric Resonator Research Articles

Axial magnetic quadrupole mode of dielectric resonator for omnidirectional wireless power transfer

To achieve omnidirectional wireless power transfer (WPT) with high efficiency, a high Q-factor transmitter generating homogeneous magnetic field is crucial. Traditionally, orthogonal coils of different shapes are used to realize transmitters. In this paper, we develop an omnidirectional magnetic resonant WPT system based on a dielectric disk resonator with colossal permittivity and low loss operating at the axial magnetic quadrupole mode. The constant power transfer efficiency of 88% at the frequency of 157 MHz over the transfer distance of 3 cm for all azimuth angles of a receiver is experimentally demonstrated. The possibility of multi-receivers charging is also studied demonstrating a total efficiency of 90% regardless of azimuth angle between two receivers with respect to the transmitting disk resonator. The minimized exposure of biological tissues to the electric and magnetic fields as well as a low specific absorption rate is observed that makes the WPT system safer for charging with higher input power.

Absorbance enhancement of monolayer MoS2 in a perfect absorbing system

Absorbance of monolayer MoS${}_{2}$ is weak due to its atomic thickness. This poses an obstacle for its applications. The authors reveal numerically and experimentally that the resonance of dielectric Si nanodisks can enhance the absorbance and emission of monolayer MoS${}_{2}$. Taking into account of both the absorbance and quantum efficiency modifications by the dielectric disk resonators, their model successfully explains the observed emission enhancement under normal light incidence. An underlying gold mirror further strengthens the absorbance of monolayer MoS${}_{2}$. A perfectly absorbing structure is proposed, with 53% of the total incident power absorbed by the MoS${}_{2}$ monolayer.

Nonradiating sources for efficient wireless power transfer

Abstract Nonradiating sources of energy realized under a wave scattering on high-index dielectric nanoparticles have attracted a lot of attention in nano-optics and nanophotonics. They do not emit energy to the far-field, but simultaneously provides strong near-field energy confinement. Near-field wireless power transfer technologies suffer from low efficiency and short operation distance. The key factor to improve efficiency is to reduce the radiation loss of the resonators included in the transmitter and receiver. In this paper, we develop a wireless power transfer system based on nonradiating sources implemented using colossal permittivity dielectric disk resonator and a subwavelength metal loop. We demonstrate that this nonradiating nature is due to the hybrid anapole state originated by destructive interference of the fields generated by multipole moments of different parts of the nonradiating source, without a contribution of toroidal moments. We experimentally investigate a wireless power transfer system prototype and demonstrate that higher efficiency can be achieved when operating on the nonradiating hybrid anapole state compared to the systems operating on magnetic dipole and magnetic quadrupole modes due to the radiation loss suppression.

Numerical Study of Non-Radiating Near-Field Wireless Power Transfer System

The main challenge in near-field wireless power transfer systems is the increase of power transfer efficiency. It can be achieved by reducing ohmic or radiation losses of the resonators included in the system. In this paper, we propose and investigate numerically a non-radiating near-field wireless power transfer system based on transmitter and receiver implemented as dielectric disk resonators. The transmitter and receiver geometrical parameters are numerically optimized to operate at the frequency of non-radiating state of high refractive index dielectric resonators instead of magnetic dipole mode. Under the non-radiating state, we determine the frequency with almost zero radiation to the far-field. We numerically study the wireless power transfer efficiency as a function of operation distance between the transmitter and receiver and demonstrate that the higher efficiency compared to magnetic dipole mode can be achieved at non-radiating state for a fixed distance due to suppression of the radiation loss.

Resonant Frequencies in Monolithic Radial Transmission Line

Being widely used in the design of the future Z-pinch accelerators, the monolithic radial transmission line (MRTL) is considered to have high-pass characteristic. However, it was found with 3-D electromagnetic simulation that the MRTL has resonant frequencies in high-frequency region. At the resonant frequencies, the electromagnetic wave cannot be delivered to the load. The space-time distributions of the electromagnetic field in the MRTL show that the standing waves at the resonant frequencies form azimuthally in a narrow ring near the input of the MRTL. The resonant modes in the MRTL are similar to the whispering gallery modes in the dielectric disk resonator. The phenomenon of the resonant frequencies in the MRTL was confirmed in the experiment with a small MRTL. The study on the resonant frequency of the MRTL is helpful for a further understanding of MRTL and designing the MRTL reasonably.

Spin–Spin and Spin–Phonon Interaction as a Nature of Microwave Absorption in He II

Experimentally observed with dielectric disk resonator technique, microwave absorption–amplification in liquid He II below $$\lambda $$ -point has been interpreted theoretically as a phenomenon in electrically active dielectric medium with low-energy excitations which exist near the ground state of the four-electron He–He interatomic bond due to spin–spin and spin–phonon coupling. The experimentally registered microwave absorption line is $$f_0=180.3\,\hbox {GHz}$$ at $$T=1.4\,\hbox {K}$$ and $$f_0=150.0\,\hbox {GHz}$$ at $$T=2.1\hbox {K}$$ which strongly corresponds to the values of roton gap known from neutron diffractometry. Our theoretical estimation gives only an upper limit $$>250\,\hbox {GHz}$$ for resonant response of the system. We interpret the dielectric $$^4\hbox {He}$$ superfluid as a working substance for low-temperature MASER and clarify the atomic mechanism of microwave absorption–amplification in the condensed helium phases.

Increasing Q-Factor of Planar Dielectric Resonators with Whisper Gallery Modes

Planar dielectric resonators (DR) with height significantly lower than the operating wavelength are investigated as a new class of disk dielectric resonators of the millimeter wavelength range with whispering gallery (WG) modes. It is known that in the open state, such resonators based on the WG modes are not excited due to high radiation losses. It is shown that the solution of this problem is the partial shielding of the disk dielectric structures with a plane-parallel screen by placing the disk between two flat conducting mirrors. It has been established that by introducing an air gap between the flat base of the dielectric disk and one of the conductive mirrors, it is possible to increase the quality factor of the planar DR almost twice. One of the reasons for this is the partial displacement of the resonant field of the WG modes from the dielectric region to the air gap, where the dielectric losses are lower. In addition, an increase in the air gap in the range of optimal values, comparable to half the working wavelength, leads to a decrease in ohmic losses. The above causes an increase in the quality factor of planar DR as an air gap is extended.

Eigen-frequencies of whispering gallery modes of disk dielectric resonators: a dimensional quantization method

A method for calculation of the resonant frequencies as well as free spectral range was developed for the high-Q whispering gallery mode disk dielectric resonators. The method is based on application of the size quantization to the dispersion equation derived for an infinite dielectric cylinder. The size quantization is caused by the requirement of the phase balance for standing waves in the resonator.

Система соосных дисковых диэлектрических резонаторов с азимутальными колебаниями

The own q-factor of a disk dielectric resonator (DDR) with azimuthal oscillations is determined by the radiation losses from the disk surface and dissipation in the dielectric. A change of disk parameters reducing the influence of one of these factors invariably causes an increased influence of the other parameter, whereas the own q-factor does not exceed 1/tgδ of the disk material. In a resonant structure made in the form of two coaxially arranged disks, the q-factor may be several times higher than this value. That the effect is in principle possible is obvious: in a multilayer structure with different dissipation in layers, it is possible to localize the electromagnetic field in an area with low dissipation. Preliminary experimental studies have shown that the effect does take place and depends on the choice of the working type of azimuthal oscillations and system parameters. The aim of this study is to justify the choice of the type of azimuthal oscillations and the region of structural parameters with which the highest levels of the own q-factor are obtained. For calculating the characteristics of azimuthal waves of the HE- and EH types producing oscillations in the DDR system, the phenomenological method of effective dielectric permeability was used. A system of distributed coupled planar dielectric waveguides and a dielectric cylinder were considered as the method’s first and second models, respectively. The results from an analysis of dispersion and energy characteristics of the own types of azimuthal resonators have shown that the highest levels of own q-factors are characteristic of an even EH-type and can be several times higher than 1/tgδ.

Wireless power transfer based on dielectric resonators with colossal permittivity

Magnetic resonant wireless power transfer system based on dielectric disk resonators made of colossal permittivity (ε = 1000) and low loss (tan δ = 2.5 × 10–4) microwave ceramic is experimentally investigated. The system operates at the magnetic dipole mode excited in the resonators providing maximal power transfer efficiency of 90% at the frequency 232 MHz. By applying an impedance matching technique, the efficiency of 50% is achieved within the separation between the resonators d = 16 cm (3.8 radii of the resonator). The separation, misalignment and rotation dependencies of wireless power transfer efficiency are experimentally studied.

Радиационные потери элементов связи зеркального дискового диэлектрического резонатора. Часть 2. Связь с рассогласован-ными волноводами

Радиационные потери элементов связи зеркального дискового диэлектрического резонатора. Часть 2. Связь с рассогласован-ными волноводами

Радиационные потери элементов связи зеркального дискового диэлектрического резонатора. Часть 1. Связь с согласованными волноводами

Радиационные потери элементов связи зеркального дискового диэлектрического резонатора. Часть 1. Связь с согласованными волноводами

The effect of gap width between disks on the Q value of a laminar dielectric disk resonator

The influence of the gap width between disks on the Q value and resonance frequency shift of a laminar dielectric disk resonator operating on whispering-gallery modes has been studied. It is established that an increase in the air gap between disks leads to growth in resonance frequency f of the selected mode and can increase the Q value of the laminar dielectric disk resonator as compared to that of an analogous usual (monolithic) disk resonator.

Nonmetallic Dielectric Resonator Antenna Using Carbon Nanotube Composite Materials

In this letter, we present a nonmetallic antenna for wireless applications comprising a circular disk dielectric resonator (DR) on a duroid substrate, with carbon nanotube (CNT) composite material. The radiation characteristics of the proposed DR-CNT antenna such as impedance bandwidth and peak gain are studied both numerically and experimentally. The effect of the ohmic losses in the CNT composite on the antenna efficiency is investigated. The DR-CNT antenna has useful gain and radiation characteristics over the operating frequency band near the resonance of DR, and therefore the proposed antenna is a good candidate for wireless applications requiring a nonmetallic antenna.

Determination of dependences for eigen frequencies of resonator

The rigorous methods of disk dielectric resonators have not been realized. The main reason is that the natural oscillations of the resonator should be considered in an unlimited region and should satisfy the radiation condition at the infinity. The “whispering gallery” HE nml oscillations were studied for various values of the azimuth index n . The attention was focused on the dependence of the resonance frequencies and radiation quality factors from the change of resonator thickness. Using the characteristic equation, an approximate formula, relating the resonance frequency with geometric and electrodynamic parameters of the resonator, was obtained. It was determined that the resonance frequencies, at which the tangential components of the electric field are close to zero on the side surface of the resonator, correspond to the values of the resonator thickness, at which a maximum radiation quality factor is observed.

Whispering-gallery-mode resonance sensor for dielectric sensing of drug tablets

We propose, for the first time, the application of whispering gallery mode (WGM) perturbation technique in dielectric analysis of disk shape pharmaceutical tablets. Based on WGM resonance, a low-cost high sensitivity sensor in milllimeter-wave frequency range is presented. A comprehensive sensitivity analysis was performed to show that a change in the order of 10−4 in the sample permittivity can be detected by the proposed sensor. The results of various experiments carried out on drug tablets are reported to demonstrate the potential multifunctional capabilities of the sensor in moisture sensing, counterfeit drug detection and contamination screening. Analytically, two sample placement configurations, i.e. a tablet placed on top of a dielectric disk resonator and inside a dielectric ring resonator, have been studied to predict the resonance frequency and Q-factor of the combined sample-resonator structure. The accuracy of the analytical model was tested against full-wave simulations and experimental data.

Effect of random surface inhomogeneities on spectral properties of dielectric-disk microresonators: Theory and modeling at millimeter wave range

The influence of random axially homogeneous surface roughness on spectral properties of dielectric resonators of circular disk form is studied both theoretically and experimentally. To solve the equations governing the dynamics of electromagnetic fields, the method of eigenmode separation is applied previously developed with reference to inhomogeneous systems subject to arbitrary external static potential. We prove theoretically that it is the gradient mechanism of wave-surface scattering that is highly responsible for nondissipative loss in the resonator. The influence of side-boundary inhomogeneities on the resonator spectrum is shown to be described in terms of effective renormalization of mode wave numbers jointly with azimuth indices in the characteristic equation. To study experimentally the effect of inhomogeneities on the resonator spectrum, the method of modeling in the millimeter wave range is applied. As a model object, we use a dielectric disk resonator (DDR) fitted with external inhomogeneities randomly arranged at its side boundary. Experimental results show good agreement with theoretical predictions as regards the predominance of the gradient scattering mechanism. It is shown theoretically and confirmed in the experiment that TM oscillations in the DDR are less affected by surface inhomogeneities than TE oscillations with the same azimuth indices. The DDR model chosen for our study as well as characteristic equations obtained thereupon enable one to calculate both the eigenfrequencies and the Q factors of resonance spectral lines to fairly good accuracy. The results of calculations agree well with obtained experimental data.

ESR-Cell Based on Disk Dielectric Resonator with Tunable Marker

The technique of detecting the Electron Spin Resonance (ESR) response separately from the magnetic specimen under study and for the ESR-marker placed into the resonator without destroying its geometrical parameters is offered. The disk dielectric resonator (DDR) is proposed as an adequate resonator cell. The reliability of technique is demonstrated both theoretically and experimentally.

The spectrum of whispering-gallery modes with large azimuthal indexes in thin disk dielectric resonators

The dispersion and resonance characteristics of whispering-gallery modes in a resonator with a small height-to-radius ratio are investigated theoretically and experimentally. It is shown that the calculated mode frequencies and azimuthal indexes match the experimental data obtained in the millimeter-wave range for resonators fabricated from certain materials. A maximum is revealed in the dependence of frequency intervals between neighboring modes on the azimuthal index at large values of the latter.

Physical configuration and performance modeling of all-dielectric metamaterials

In this paper, physical concept and performance analysis of all-dielectric metamaterials are presented. Metamaterials with desired material parameters $(\ifmmode\pm\else\textpm\fi{}\ensuremath{\epsilon},\ifmmode\pm\else\textpm\fi{}\ensuremath{\mu})$ are developed by creating electric and magnetic resonant modes. Dielectric disk and spherical particle resonators are considered as the great candidates for establishing the dipole moments (metamaterial alphabet). A full wave finite difference time domain technique is applied to comprehensively obtain the physical insights of dielectric resonators. Near-field patterns are plotted to illustrate the development of electric and magnetic dipole fields. Geometric-polarization control of the dipole moments allows $\ensuremath{\epsilon}$ and $\ensuremath{\mu}$ to be tailored to the application of interest. All-dielectric double negative metamaterials are designed. Engineering concerns, such as loss reduction and bandwidth enhancement are investigated.