Dielectric Spherical Shell Research Articles

Periodic and chaotic vibrations of dielectric elastomer spherical shells considering structural damping

Periodic and chaotic vibrations of dielectric elastomer spherical shells considering structural damping

Electromagnetic field analysis of shielded composite dielectric spherical shell resonator in infrared and visible regions

In this paper, we have presented an electromagnetic field analysis of shielded composite dielectric spherical shell resonator. The resonator studied in this work is considered for the first time as no study on such resonators is available in the published literature to the best of the author's information. This shielded composite dielectric spherical shell resonator is composed of two concentric metal spheres with different dielectric material has been made. The whole assembly is shielded by a perfectly conducting concentric spherical metal. The expression for the resonant frequencies and quality factors have been calculated using numerical methods for both the TEnmℓand TMnmℓ modes for an infrared and visible regions. It is found that as the outer radius of the shielded composite dielectric spherical shell resonator increases, the quality factor Q of the resonator increases monotonically. It is also found that if we change the radius of the inner dielectric sphere, there is no appreciable change in resonant frequency of the concerned mode is observed. This is due to the small difference in the permittivities of the materials of the inner and the outer dielectric spheres. It has also been observed that an inner concentric superconducting sphere within a dielectric spherical resonator is a more effective controlling parameter of the resonant frequency than the other parameters.

Shielded Composite Dielectric Spherical Shell Resonator with a Concentric Metal Sphere at the Centre

Shielded Composite Dielectric Spherical Shell Resonator with a Concentric Metal Sphere at the Centre

Resonant and normal modes behavioral studies of shielded dielectric spherical shell resonator

Electromagnetic theory has been used to derive characteristic equations for the shielded dielectric spherical shell resonator with a concentric metallic sphere at the center. Expressions for the quality factors have also been derived. Using these expressions for the characteristic equations and quality factors numerical computations have been carried out for the resonant frequencies and the quality factors for the TEnmℓ and TMnmℓ modes using numerical methods. It is found that as the outer radius b of the shielded dielectric spherical shell resonator is increases, the resonant frequency for a given mode decreases. It has also been observed that the quality factor increases as the outer radius b of the dielectric resonator increases. As a result of high quality factor there is fractional increase in the energy stored in the dielectric sphere is more compared to the fractional increase in the total power loss through the metal surfaces and the dielectric volume, which improves the spectral characteristics.

Artificial isotropic magnetism and negative refraction of metamaterial consisting of dielectric spherical shells

We present a detailed study on the artificial magnetism of high-permittivity dielectric spherical shell array and the negative refraction behavior of the composite consisting of dielectric spherical shells and metal wire lattice. The spherical shell array in cubic lattice arrangement can exhibit an isotropic negative magnetism when excited into magnetic dipole resonance. When the dielectric spherical shell and metal wire lattice are combined in a body-centered cubic structure, full-wave simulations show that the bulk metamaterial with this structure can exhibit a negative refraction behavior. It is shown that artificial magnetic response can originate from differently structured dielectric elements, similarly to the conventional metamaterial constituents based on metal resonance structures.

The characteristics and stability of a dielectric elastomer spherical shell with a thickwall

When a voltage is applied between the internal and external surface of a dielectricelastomer spherical shell, positive charges appear on one surface and negativecharges on the other. This gives rise to Coulomb forces between opposite charges,generating a pressure. Thus, the shell reduces in thickness and stretches in area, anda higher electric field is produced. This positive feedback may make the shellcontinually thin down, eventually causing electrical instability. In this paper we use theneo-Hookean model and the Arruda–Boyce model to analyze the electromechanicalinstability of the thick-walled shell respectively. The electric field in the shell isinhomogeneous and varies with the radius of the shell. The instability in sphericalshells with different thicknesses and boundary conditions is discussed. When theelastomer obeys the Arruda–Boyce model, the stability is related to the parametern. Thespherical shell will appear with snap-through instability and pull-in instability for different values of theparameter n.

Dynamics of a thick-walled dielectric elastomer spherical shell

The nonlinear vibration response of a thick-walled spherical shell subjected to the mechanical pressure and electric field is studied in this paper. When subject to an electric field through the thickness of the spherical shell, the material expands in plane and contracts in thickness. The dielectric elastomer is assumed to be isotropic and neo-Hookean. Based on simple geometrical and spherical capacitor assumptions, we deduce an explicit analytical equation of motion of the dielectric elastomer spherical shell. The dynamic behaviors of the spherical shell under a constant electric loading and periodic electric loading are analyzed. In addition, the critical voltage is calculated in terms of various loading.

Analysis of the optical force dependency on beam polarization: dielectric/metallic spherical shell in a Gaussian beam

We carry out a detailed numerical simulation study to investigate the dependency of optical force on beam polarization. Using the well-known finite-difference time domain method and Maxwell's stress tensor, we consider general dielectric (e.g., glass) or metallic (e.g., gold) spherical shells immersed in a Gaussian optical beam. Our results show that TE and TM polarized Gaussian beams exert different amounts of optical force depending on the shell dimensions and material properties. We specifically show that purely dielectric shells do not experience different optical forces due to polarization differences but TM polarized beams exert higher optical force on metallic shells than equivalent TM polarized beams.

Complete photonic bandgaps in the visible range from spherical layer structures in dichromate gelatin emulsions

We have fabricated spherical layer structures that exhibit complete photonic bandgaps in the visible range in dichromate gelatin emulsions by holographic interference. The complete bandgap was not a result of the high dielectric contrast but was due to the fact that the spherical layer structure was isotropic with equal spacing in all accessible directions. Angular dependence spectral measurements of the spherical layer structures were in good agreement with the expected results from an ideal structure of dielectric concentric spherical shells with equal spacing. Our fabrication technique and results could pave the way for new applications using complete bandgap photonic crystals.

The case of the disappearing magnetic dipole

The problem of an oscillating magnetic dipole at the centre of a lossless dielectric spherical shell is considered. For simplicity, the free-space wavelength is taken to be much greater than the shell radii, but the relative permittivity εr of the shell is taken as much greater than unity, so the wavelength in the shell could be comparable with its dimensions. The vector potential in all regions is found. Under certain conditions, involving the shell radii, the frequency and εr, the vector potential outside the shell appears to be infinite. This is impossible, so one must conclude that the dipole moment vanishes. This result, a ‘disappearing dipole’, although strange, can be justified. Although this paper is aimed primarily at readers with a strong interest in fundamental physics, it could be introduced as an interesting result in an undergraduate course on electromagnetism.

Surface plasmon polaritons and its coupling with cavity mode in the system of dielectric spherical shells periodically mounted in a metal substrate

We investigate the surface plasmon polaritons and its coupling with other electromagnetic modes by observing the absorption spectrum on a system of dielectric spherical shells periodically mounted in a metal substrate. We found that there exist two resonance frequencies in the system corresponding to surface plasmon polaritons mode and cavity mode. At these frequencies, we can find related peaks i n absorbance. Since the surface plasmon polaritons cannot couple with the incide nt plane wave directly and both couplings of the cavity mode with the incident w ave and the surface plasmon polaritons are also weak, so the strength of absorpt ion peaks are generally very limited. However, we can adjust some parameters in the system to make the surface plasmon polaritons and the cavity mode with almos t the same frequency. In this case, the coupling can be dramatically enhanced, a nd we can observe very strong peaks in absorbance. The relationships of resonanc e absorption with some physical and geometrical parameters are discussed in deta il.

Characterization of electromagnetic scattering by a plasma anisotropic spherical shell

Scattering of a plane wave by a plasma anisotropic spherical shell is considered in this paper and scattered fields are obtained in spherical coordinates. The electromagnetic fields in a plasma medium and in a free space are expanded in terms of the spherical vector wave functions (SVWFs) for a plasma anisotropic medium and the SVWFs in an isotropic medium. Numerical results for very general properties of the plasma dielectric material spherical shells are given. And those results obtained in a special case using the present method and the method integrating the method of moments (MoM) and the conjugate-gradient fast-Fourier-transform (CG-FFT) approach are compared, and a very good agreement is found. The results presented here can be used in antenna design, satellite communications channel design and characterization, and target shielding studies.

Time-Frequency Analysis of Electromagnetic Pulse Response from a Spherical Target

Transient backscattering from a spherical target underincidence of an electromagnetic short pulse is studied. The target canbe a perfectly conducting sphere, a dielectric sphere or a dielectricspherical shell. To understand the scattering mechanism from transientimpulse echoes for target detection, both the short-time Fouriertransform (STFT) and the wavelet transform (WT) are applied toretrieval of scattering information from the backscattering data.Analysis in both the time and frequency domains demonstrates that theWT is more feasible than the STFT to clarifying scattering process ofthe scatterer because of its excellent multi-resolution characteristic.This technique shall be helpful for scattering analysis and detectionof more complex single or multi-targets.

Laser-trapping properties of dual-component spheres.

The optical trapping properties of dual-component spheres consisting of a cocentered outer transparent dielectric spherical shell and internal solid sphere are examined on the basis of the enhanced ray optics model. It is shown that stable trapping can occur on axis, off axis, or at multiple axial positions and depends on the dual-sphere and laser beam parameters. Computation results are also presented for an internal reflecting sphere surrounded by an outer dielectric spherical shell.

Transient interactions of an EM pulse with a dielectric spherical shell

The authors study the scattering interaction of short electromagnetic pulses with a spherical target. The target is assumed penetrable and they model it as an air-filled dielectric shell. The radar cross-section (RCS) of such a target is obtained and its resonance features are analyzed. A dielectric composition makes the resonance features become very prominent compared with the case of a perfectly conducting sphere. When the interrogating waveform is a pulse of short duration, the resonance features of the RCS can be extracted within the frequency band of the spectrum of the incident pulse. To verify their theoretical predictions they illuminate spherical targets with short, broadband pulses using an impulse radar system. The actual shape of the pulse that is incident on the targets is theoretically modeled using a digital filter design technique together with pulse returns from a reference target. They verify that the shape of the predicted, backscattered pulse that results from their design method agrees well with the experimental findings using three additional targets of different sizes and materials. They investigate in the combined time-frequency domain the development in time of the various frequency features of the spectra of backscattered pulses using time-windowed Fourier transforms. The methodology developed can handle broadband pulses of any sufficiently smooth spectrum, interacting with (lossy or lossless) dielectric scatterers, and can extract resonance features within the frequency band of the spectrum of the transmitted pulse. Accordingly, this method could be also used for assessing the performance of high-power impulse radar systems. >

Surface Dielectric Response of Collective Plasmon Excitations in C60Fullerite

Abstract The paper begins with a review of available observations from electron-energy-loss spectroscopy (EELS) on the excitation of multipolar plasmons in C60. With these observations in the background, an electrodynamic formalism is developed for computing the response of collective plasma oscillations in a fullerite film subject to an external electric field. This formalism allows us to construct the dielectric response function relevant for applications to EELS in specular-reflection geometry. The only input required by the theory is a set of dynamical multipolar polarizabilities of an isolated molecule, which could be provided by a separate theory but which we simulate here by an empirical model consisting of a dielectric spherical shell. The surface loss function is computed for an fcc (111) film composed of such dielectric shells. Comparison with the few available experimental data indicates that quadrupole and higher-multipolar plasmons in fullerites contribute significantly to the long-range inel...

Radiation from a radial dipole through a thin dielectric spherical shell

The radiation from and the reaction on a radial dipole placed inside a thin dielectric spherical shell are investigated. Numerical results have been obtained for the gain pattern and the impedance change of an elementary dipole. The nearer the center of the shell the dipole is placed, the less the pattern is found to be influenced by the shell, the opposite being the case for the impedance of the dipole.