Electromagnetic surface waves in a metallised ferrite slab

The propagation of electromagnetic surface waves in a metallised ferrite?dielectric sandwich is described. The computed dispersion curve is found to be critically dependent on the dielectric-slab thickness. The theoretical results are illustrated by measuring the direct and reverse r.f. transmission through a polycrystalline y.i.g. slab as functions of the frequency.     

Electromagnetic surface waves of a ferrite slab bounded by metamaterials

The dispersion characteristics of electromagnetic surface waves (EMSWs) supported by a ferrite film of finite thickness magnetized parallel to the planes of its interfaces with metamaterial (MTM) surroundings are numerically investigated. MTMs have simultaneously negative permeability μ$\mu$ and negative permittivity ?$?$. The dispersion equation is analytically derived and magnetostatic approximation is considered. The surface wave frequency is plotted against the effective index for different slab thicknesses. In the calculation, several sets of ?$?$ and μ$\mu$ of the metamaterial are considered with their products kept constant, i.e., ?μ=4$?\mu =4$. Results show that wave in microwave range can only satisfy the condition of negative effective permeability of the ferrite slab. Surface waves propagate through the film for the considered values of ?$?$ and μ$\mu$. The waves’ behavior depends on the values of ?$?$ and μ$\mu$ of the MTMs, e.g., a discontinuity may appear and disappear in the curve of the frequency versus effective index at different values for film thicknesses.     

Electromagnetic surface waves supported by a half-space of a counterstreaming plasma

The characteristics of electromagnetic surface waves supported by a plane interface separating a semi-infinite region of free space from another semi-infinite region consisting of a plasma counterstreaming parallel to the interface are investigated for the case in which the wave is progressing parallel to the direction of the streams. The behaviour of the surface waves is quite different from the case in which the plasma is stationary. The surface waves exist for all frequencies. The phase velocity of the surface wave is equal to the electromagnetic wave velocity in free space for very low frequencies, decreases monotonically as the frequency is increased and asymptotically approaches the velocity of the stream for very high frequencies. The surface waves are always stable. In contrast to on unbounded counterstreaming plasma which gives rise to instability for the plane longitudinal wave progressing parallel to the streams, a half-space of counterstreaming plasma does not give rise to any instabilities for waves progressing parallel to the streams.     

New unidirectional transducer and broadband reflector of acoustic surface waves

An acoustic-surface-wave multistrip coupler, formed into the shape of a U, may be used on materials of high electro-mechanical coupling coefficient to convert a bidirectional interdigital transducer into a unidirectional transducer with negligible loss of bandwidth. The U-shaped coupler by itself acts as a normal-incidence mirror, and can have a reflection loss of less than 2 dB over a 60% bandwidth. Both devices are constructed of evaporated aluminium by existing photolithographic techiques. No special polishing operations or extra electrical components are required.     

Electromagnetic waves in Faraday chiral media

Plane wave propagation in two kinds of Faraday chiral media, where Faraday rotation is combined with optical activity, is studied to examine methods of controlling chirality. The two types of media studied are magnetically biased chiroplasmas and chiroferrites. For propagation along the biasing magnetic field, four wavenumbers and two wave impedances are found which are dependent on the strength of the biasing field. Dispersion diagrams for the chiroplasma case are plotted. Propagation at the plasma frequency of the chiroplasma is also investigated     

Electromagnetic waves in cylindrical plasma-dielectric structures

The theory of electromagnetic waves in cylindrical structures (waveguides) with plasma and plasma-dielectric fillings is presented in a systematic form. The case of isotropic cold electron plasma with sharp transverse plasma/vacuum, plasma/dielectric, plasma/plasma, and plasma/metal interfaces is considered. Particular attention is given to surface plasma waves and their interaction with bulk electromagnetic modes. The coupling of E and B waveguide modes that is due to the transverse inhomogeneity is investigated. The important question of the applicability of the potential (electrostatic) approximation in the theory of plasma waves and the role of nonpotential effects are discussed. Original Russian Text ? A.F. Aleksandrov, M.V. Kuzelev, A.A. Rukhadze, 2008, published in Radiotekhnika i Elektronika, 2008, Vol. 53, No. 12, pp. 1445–1465.     

The relation between creeping waves, leaky waves, and surface waves

In this paper, we examine the creeping wave propagation wavenumbers, modal impedance, and field behavior on a dielectric coated circular cylinder. The physical interpretation is assisted by comparing the cylinder's pole waves with the leaky waves and surface waves that occur on a flat, grounded dielectric slab. The propagation wavenumbers and modal impedance are computed in the complex wavenumber plane. The cylinder propagation wavenumbers come from a transcendental equation involving Hankel functions, which are entire functions of complex order, whereas for the slab, branch-point singularities are present. This difference is examined, so that one can better understand how a coated cylinder behaves like a flat slab, when the cylinder radius is large. It is found that for the cylinder, the Stokes line for the asymptotic expansion of the Hankel function plays a role that is similar to the planar slab branch cut.     

电子出射波重构的基本原理和应用

随着场发射枪透射电子显微镜的普及，电镜的信息分辨极限和点分辨率成为表征电镜分辨本领的两个重要指标。由于电镜衬度传递函数的振荡特性，用场发射透射电镜拍摄的高分辨像在其点分辨率和信息分辨极限之间的信息很难解释。电子出射波重构就是通过拍摄系列欠焦高分辨像，计算获得电子离开样品表面的出射波函数，将电镜的分辨本领由点分辨率延伸到其信息分辨极限，井消除球差、欠焦、像散等影响，有望在中等电压电镜上获得近埃、乃至亚埃级可直接解释的高分辨像，实现C、N、O等轻元素单原子列探测，为今后定量电子显微学研究奠定基础。     

Electromagnetic waves of dielectric structures in plasma

The electromagnetic waves of a dielectric layer and of a dielectric cylinder in homogeneous infinite plasma are considered. The dispersion dependences of surface and volume-surface E and H electromagnetic waves are investigated. A classification of the waves of dielectric structures in plasma is proposed.     

New results for the properties of TE surface waves in absorbinglayers

TE surface waves in absorbing layers with high losses are studied. All basic characteristics of these waves are analyzed. They include attenuation and propagation constants, electric and magnetic losses, complex Brewster angles, phase and amplitude fronts of Brillouin waves inside layers, phase and energy velocities. New phenomena of the upper frequency cutoff and merging of higher order modes are demonstrated. In addition, the excitation of TE surface waves in thin absorbing layers is investigated and the launching efficiency is computed     

Electromagnetic waves and oscillations in the layered semiconductor-dielectric-semiconductor structure

Theoretical and numerical studies of the electromagnetic properties of the layered semiconductor — dielectric — semiconductor (SDS) structure was carried out. It was shown that the weak damping guide and surface waves may exist in this structure and retardation of surface waves may be several times more than for the semiconductor — dielectric (SD) interface. If this structure contains reflections it leads to the formation of high Q-factor resonance oscillations. It was found that at the beginning of intermode coupling of two surface oscillations in the studied resonance structure, hybrid surface oscillations with near resonance frequencies are formed. Their electromagnetic field components along the wave propagation direction are orthogonal to each other and modulated along the SD interface by orthogonal envelopes.     

New high-coupling low-diffraction cut for acoustic surface waves on LiNbO3

The existence of a new high-coupling low-diffraction-loss cut for acoustic surface-wave propagation on LiNbO3 has been theoretically predicted and experimentally verified. The propagation direction lies 16?° from the Z axis with the plate normal 16?° from the negative Y axis.     

New nonlinear magnetostatic surface waves in a ferromagnetic (YIG)

The general propagation characteristics of magnetostatic surface waves guided by a single interface of a semi-infinite nonlinear dielectric cover and a ferromagnetic substrate (YIG) have been derived. The nonlinear dielectric cover has intensity dependent refractive indices. The magnetostatic approximation is considered and retardation is ignored in describing the electromagnetic fields in the structure. The used magnetostatic approximation is leading to new waves and might be called nonlinear magnetostatic surface waves. The propagation of these waves is non-reciprocal in contrast to the linear magnetostaic surface waves, which had been only found in the negative direction of propagation.     

Electromagnetic humidity sensor for industrial applications

The letter describes an electromagnetic humidity sensor based on a resonance perturbation technique. The proposed sensor is capable of measuring humidity over a wide dynamic range in an industrial environment and is insensitive to dust, dirt, oil vapours etc. The all-metal construction of the sensor makes it immune to damage by high temperature. The sensor signal processing circuit provides a time-dependent signal which can be directly applied to any modern computerised control systems.     

Electromagnetic radiation and scattering from finite conducting anddielectric structures: surface/surface formulation

An efficient and accurate numerical procedure for the analysis of the electromagnetic scattering and radiation from arbitrarily shaped, composite finite conducting and dielectric bodies is proposed. A set of coupled electric field integral equations involving surface equivalent electric and magnetic currents is used. The coupled integral equations are solved through planar triangular patch modeling and the method of moments. Two separate, mutually orthogonal vector functions for each edge connecting a pair of triangular patches have been developed. Numerical results for disk/cone and cylinder/cone structures are compared with other available data. Limited comparison with experimental data has also been made     

Waveguides for acoustic surface waves: A review

A review is presented of the current state of knowledge concerning waveguiding structures for acoustic surface waves. The stress is on the various types of waveguide and their properties, in order to provide a guide for the applications-oriented engineer. Related matters which are treated more briefly include the reasons for using waveguides, and some applications, both actual and potential.