Homogenization of nanostructured media in magnetic field

Problem of homogenization of nanostructured media in magnetic field has been considered. Possibility of introduction of effective material parameters dielectric permittivity and magnetic permeability for three classes of media such as magnetic metal nanostructures, film metal–dielectric composite media and 3D-nanocomposites on the base of opal matrices has been investigated. It has been stated that the introduction of effective parameters far from magnetic resonance conditions is possible at millimeter waveband frequencies. Strict introduction of effective magnetic permeability of nanostructured media near magnetic resonance is not possible.     

Theoretical investigation of resonance frequencies in long wavelength electromagnetic wave scattering process from plasma prolate and oblate spheroids placed in a dielectric layer

Response of a prolate spheroid plasma and/or an oblate spheroid plasma in presence of long wavelength electromagnetic wave has been studied. The resonance frequencies of these objects are obtained and it is found that they reduce to the resonance frequency of spherical cold plasma. Moreover, the resonant frequencies of prolate spheroid plasma and oblate spheroid plasma covered by a dielectric are investigated as well. Furthermore, their dependency on dielectric permittivity and geometry dimensions is simulated.     

Sensitivity of Homogeneity Mapping of Semiconducting Wafer Using Millimeter Waves

The homogeneity mapping by measuring the phase or the amplitude of millimeter wave reflected from or transmitted through the semiconducting wafer is considered. The sensitivity of the conductivity homogeneity mapping is determined and conditions at which conductivity inhomogeneities can be distinguished from dielectric constant inhomogeneities are established.     

Evaluation of gold nanowire pairs as a potential negative index material

A metamaterial consisting of pairs of metallic nanowires, separated by a dielectric spacer, has been fabricated and spectrally characterized in the visible and near-infrared spectral domain. It is shown, that the structure exhibits both a plasmonic and a magnetic resonance depending on its geometry and orientation with respect to the illuminating wave field. In particular, we investigate the influence of the thickness of the spacer layer on the spectral position of the resonances and show that, for an appropriate adjustment, both resonances coincide. Measurements of the amplitude and the phase of the transmitted wave are presented. It is also shown that the material is highly anisotropic with respect to the angle of incidence, as the plasmonic resonance wavelength depends strongly on it whereas the magnetic resonance does not show this sensitivity. All experimental results are supported by numerical simulations. PACS 81.07.-b; 78.67.-n; 78.20.-Ci     

Reflection and transmission of circularly polarized waves in nonlinear dielectrics

A time-sinusoidal circularly polarized plane standing wave solution is obtained for isotropic lossless dielectric media with arbitrary nonlinearity. The spatial variation of the standing wave depends on the nonlinearity and is found by solving a problem of centralforce motion in which the electric complementary energy density furnishes the potential and the spatial coordinate has the role of time. Two special nonlinear dielectric response laws-cubic and quintic-are treated, and explicit solutions for the spatial variation of the wave amplitude and phase are obtained in terms of elliptic functions and elliptic integrals, respectively. The standing-wave solution is applied to give steady state solutions of two reflection/transmission problems (a) reflection from, or resonance modes between, ideally conducting planes and (b) reflection and transmission at a plane interface between two nonlinear dielectric media.     

横电波激励下亚波长一维金属光栅的异常透射性

针对一维亚波长金属光栅异常透射现象实现的问题,利用时域有限差分法,对横电波（TE波）激励带电介质的亚波长一维金属光栅的光场分布进行了模拟分析,得到了TE波的透射率与电介质折射率的变化关系,从而发现TE波在所研究的模型下具有异常透射现象.基于导模共振理论建立了类导模共振理论,并应用该理论较好地解释了TE波在所研究模型下的异常透射现象,确定类导模共振是TE波产生异常透射性的主要原因.应用所建立的理论解决了传统透射理论无法解决的问题.类导模共振理论揭示了异常透射现象的物理本质,为进一步研究异常透射性的物理本质提 关键词： 金属光栅 横电波 异常透射 类导模共振     

基于平面波导激励的修正长程表面波的传感器研究

为了解决传统的强度检测型波导激励的表面等离子体共振传感器灵敏度不高的缺点,研究平面波导激励的介质膜-金属-被测介质的可激发修正的长程表面等离子体波结构。采用离子交换的方法制备折射率可用费米函数拟合的平面波导,研究了离子交换时间对平面波导的模数及等效折射率等特性的影响,为激励波导的优化设计提供有效依据。采用制备的平面波导激励介质膜-金属-被测介质的非对称结构,研究金属材质、介质膜厚和金属膜厚等因素对修正的长程表面等离子体波特性的影响,对被测溶液的折射率进行检测。实验结果表明,其灵敏度为传统的强度检测型表面等离子体共振传感器的6倍,并且具有较好的线性关系。     

Scattering from an eccentric system,including a dielectric rod placed in a thin annular magnetized relativistic rotating electron beam (TAMRREB)

The electromagnetic wave scattering from a dielectric rod placed in a non-coaxial thin annular magnetized relativistic rotating electron beam is simulated. The resonance frequency shift and the effective factors on it are investigated. In addition, the dependencies of pattern of scattering to the plasma frequency, the rotating frequency, geometrical dimensions and dielectric constant of dielectric rod have been investigated. The eccentricity effect on the resonance frequencies is studied.     

Effect of a dielectric film on the characteristics of an open Fabry-Perot resonator cavity

It is demonstrated that placing a thin dielectric film inside the cavity of an open Fabry-Perot resonator, at an angle to its axis, will remove the polarizational degeneracy of the principal TEM_q00 oscillation modes. Upon excitation of such a resonator cavity by a plane wave, the reflected electromagnetic field is in general elliptically polarized. The shape of the resonance curve depends on the thickness of that film, on its orientation inside the cavity, on the conditions under which the cavity has been excited, and on the conditions under which the reflected signal appears in the receiver. Changing the polarization plane of the incident plane wave does not result in a smooth variation of the resonator Q factor.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 11, pp. 1648–1652, November, 1978.     

Instability of a tubular electron beam moving over a dielectric cylinder

The mechanism of interactions between the eigenwaves of a dielectric cylinder and a nonrelativistic tubular electron beam moving over its surface has been considered theoretically. A dispersion relation for the coupled waves of beam electrons and the dielectric cylinder has been derived. The conditions for coupled wave instability have been formulated and an expression for instability increments has been found. It follows from the dispersion relation and the expression for the increments that electric waves with high azimuthal indices are excited most effectively at a narrow gap between the beam and cylinder.     

介质光栅导模共振耦合波分析

导模共振是由于光栅介质内高级次子波耦合进光栅所支持的泄漏模中,导致传播波能量重新分布的结果.采用严格的耦合波方法,通过分析波导的导波模式,正确估计出弱调制介质光栅导模共振的位置.并对导模共振与光栅厚度、基底厚度以及入射角的关系作了讨论.通过采用抗反射设计,获得了具有对称、低旁带特点的窄带共振峰 关键词： 导模共振 耦合波     

Modelling of sensitivity of plasmon sensory elements based on silver nanoparticles obtained by laser evaporation and ablation

A comparison of the sensitivity of the spectral position of plasmon resonance calculated by numerical methods to a change in the refractive index of the environment for ellipsoidal and spherical silver nanoparticles with a dielectric shell synthesized by laser ablation has been performed. It has been shown that sensitivity is higher for nanoparticles with the shape of a prolate ellipsoid than for spherical nanoparticles. The modeling has shown that the optimal thickness of the dielectric shell should be 10–12 nm and its refractive index should be 1.6. With this, a sensitivity of the plasmon sensor of 32 nm/RIU (RIU is refractive index unit) may be provided.     

Modelling of isotropic double negative media for microwave applications

A composite medium consisting of two sublattices of dielectric spherical particles of high permittivity and different radii embedded in a dielectric matrix of smaller permittivity are considered. It has been shown that such a composite medium reveals properties of an isotropic double negative media (DNG) in a limited frequency range, when resonance oscillations of H_III mode in one kind of particles and E_III mode in another kind of particles are excited simultaneously. The E_III resonance and the H_III resonance give rise to the magnetic dipole momentum and the electric dipole momentum correspondingly. Averaging the magnetic momentum and the electric momentum over the cells belonging to the appropriate spherical particles gives the negative permittivity and permeability. The model of diffraction of a plane electromagnetic wave on a dielectric sphere is presented and compared with the mixing rule based consideration. The results obtained are rather close. Distribution of the electromagnetic wave outside the sphere is calculated. Influence of the dispersion of the sphere size and the dielectric permittivity on the effective parameters of the DNG material is estimated.     

Magneto-optical recording on the multilayers systems with plasmon excitation

The maximization of the sensitivity of magneto-optical recording media in the short wavelength region is discussed. We show that a combination of the optimized thickness of dielectric and Ag (or CoAg) films can increase the magneto-optic Kerr effect in FeTbCo media by about five times of magnitude in the UV and blue spectral range. It has been shown that the local plasmon excited in the Ag-based films strongly enhances the magneto-optical properties in amorphous FeTbCo magnetic film. The Kerr rotation spectra get the maxima values for the resonance conditions when the local plasmon can be excited in the Ag or CoAg films.     

Experimental demonstration of isotropic negative permeability in a three-dimensional dielectric composite

Isotropic negative permeability resulting from Mie resonance is demonstrated in a three-dimensional (3D) dielectric composite consisting of an array of dielectric cubes. A strong subwavelength magnetic resonance, corresponding to the first Mie resonance, was excited in dielectric cubes by electromagnetic wave. Negative permeability is verified in the magnetic resonance area via microwave measurement and the dispersion properties. The resonance relies on the size and permittivity of the cubes. It is promising for construction of novel isotropic 3D left-handed materials with a simple structure.     

Fabry-Perot腔谐振对横电波激励下亚波长一维金属光栅的异常透射性的作用

利用时域有限差分法,对横电波(TE波)激励带电介质的亚波长一维金属光栅的光场分布进行了模拟分析,发现TE波在所研究的模型下具有异常透射现象.探究其物理本质,确定类导模共振理论是第一个峰和第二个峰产生的主要原因.在此基础上,从麦克斯韦方程出发,通过有效折射率法,确定了类Fabry-Perot(F-P)腔谐振是产生第三个峰的主要原因.从而完善了TE波在所研究的模型下产生异常透射现象的物理本质.为进一步研究TE波异常透射性的物理本质提供了一种完整的理论依据. 关键词： 金属光栅 横电波 异常透射 类Fabry-Perot腔谐振     

共振波长对导模共振生物传感器灵敏度的影响

导模共振生物传感器由于具有微型化、免标签、高通量和实时检测等优势被广泛研究。利用严格耦合波理论分析了该生物传感器对样品折射率和厚度的灵敏度随共振波长的变化规律。当样品厚度和共振波长一定时,其折射率灵敏度恒定;随着共振波长的增大,折射率灵敏度显著提高。当样品折射率和共振波长一定时,厚度灵敏度随着厚度的增加而降低,最后趋近于0;当共振波长增加时,厚度灵敏度明显提高,厚度测量范围增大。结果表明:选取较长的共振波长有利于样品的检测和分析。     

Passage of an ultrasound wave through a magnetic superlattice of finite length

The method and results of calculating the coefficient of transmission of a circular ultrasound wave through a multilayer ferromagnet/nonmagnet dielectric system with allowance for excitation of spin waves in magnetic layers are presented. The dependence of the resonance structure of the transmittance spectrum on the number of layers and the magnetic field strength has been studied.     

Free space excitation of novel “Fractional” whispering gallery mode dielectric resonators

Solutions to the main problems that limit the sensitivity of an electron magnetic resonance (EMR) spectrometer on the basis of a whispering gallery mode dielectric resonator (WGMDR) are presented. The electromagnetic losses in the transition regions between the overmoded metallic waveguide, the overmoded dielectric waveguide and the mono-mode dielectric waveguide can be avoided by the free space excitation of the resonator that is proved to be very effective for suitably designed resonators. The EMR measurements on high-dielectric-loss samples can be safely developed employing the novel class of “fractional” WGMDRs, in which the usual traveling wave resonator is modified in a structurally stationary wave resonator. Several peculiarities of a fractional WGMDR, investigated both theoretically and experimentally, evidence the advantages of the application of this class of WGMDRs to EMR spectroscopy.     

水溶液体系ESR现场测量新型电解池

设计并研制了用于水溶液体系进行电化学激发-电子自旋共振测量的电解池。以亚甲蓝溶液和聚吡咯薄膜修饰电极的现场ESR研究为例,对该电解池的性能进行了考察。实验不仅为上述两个体系的研究提供了新的信息,而且也证明电解池设计合理、控制工作电极电位准确、响应快及灵敏度高,对研究水溶液体系电化学反应中间体、特别是现场制备和研究薄膜化学修饰电极极为有用。