Single Slab Arbitrary Polarization Surface Wave Structure

A single grounded dielectric slab can support either TM or TE modes, but cannot propagate both with the same velocity. This paper concerns a modification of the single slab which enables either polarization to propagate with the same velocity. Such a structure could transmit a circularly polarized wave, and would be useful in transmission, feeder, and antenna applications. The structure consists of a grounded dielectric slab with parallel metal plates imbedded in the dielectric, normal to and in contact with the ground plane. The plates do not reach the top of the slab. Propagation is along the plates, whereas corrugated surfaces propagate across the vanes. For small plate thickness, the TE field is undisturbed; hence, the entire slab thickness controls the velocity. The TM field, however, has an electric field component parallel to the plates, which is shorted out by the plates; thus, only the thickness of slab above the plates controls this mode, and the two modes can be independently controlled.     

Rigorous Analysis of the Scattering of Surface Waves in an Abruptly Ended Slab Dielectric Waveguide

The reflection and the scattering properties of even TE and TM surface waves incident in an abruptly ended dielectric slab waveguide are analyzed. The discontinuity is regarded as a junction between two open waveguides namely the dielectric slab waveguide and the free space waveguide. The boundary conditions acting together with the orthogonality provide singular coupled integral equations on the discrete and the continuous wave amplitudes at the discontinuity. These singular coupled intergral equations with Cauchy kernels and infinite limits of integration are solved by iteration via the Neuman series. Numerical results are presented for the reflectivity of the even TE/sub 0/ and TM/sub 0/ fundamental modes, together with their mode conversion on even TE/sub 2/ and TM/sub 2/ in a slab where two guided modes can propagate. Reflectivity and mode conversion of higher order excitations are also investigated     

On the location of leaky wave poles for a grounded dielectric slab

A simple numerical procedure for finding the loci of TE and TM leaky wave poles as the frequency or the thickness of the slab varies is presented. These loci provide important information when the integration path of the Sommerfeld integral for the grounded dielectric slab problem is deformed into the improper sheet of the Riemann surface. The accuracy of the loci has been checked extensively against contour plots of separate expressions for the electric flux density for the TE and TM cases     

Loss reduction in curved dielectric optical slab waveguide

Formulas of the pure bending loss and the transition loss valid for TM modes in dielectric optical slab waveguides are presented. The characteristic of the total transmission loss of a step-index slab waveguide containing a circular bend having an asymmetric waveguide structure are analysed numerically by applying derived loss formulas. It is found that the features of the total transmission loss of TM modes are closely analogous to those of TE modes except for small discrepancies in the numerical values.     

TE Mode Excitation on Dielectric Loaded Parallel Plane and Trough Waveguides

A theoretical and experimental study of the launching of TE surface wave modes on dielectric loaded parallel plane and trough waveguides has been performed. The source is a linear transverse current filament perpendicular to and extending across the space between the parallel side walls. Families of curves are presented, which show the bidirectional Iaunchlng efficiencies for the dominant TE modes of these two transmission lines as a function of dielectric constant, dielectric slab thickness, and current filament location. Measured bidirectional efficiencies are compared to the theoretically predicted values. Measured unidirectional launching efficiencies as high as 97 per cent were obtained for the case where a short circuit is located on one side of the current filament.     

Theory of line-source radiation from a metal-strip gratingdielectric-slab structure

This paper describes the fundamental theory of line source radiation from a source on a dielectric slab backed by a metal-strip grating. A continuous phased-array (CPA) method is applied to treat the analytic and numerical problems of antenna interaction with periodic structures. Both TE and TM mode cases for a one-dimensional strip grating are investigated. It is found that the strip grating on the dielectric surface may result in surface wave elimination and may also be used to support leaky waves. It is shown that high-efficiency and high-gain antennas on a dielectric substrate are possible with such metal-strip gratings     

Complete Polarization Conversion Characteristics of Dielectric Grating Composed of Left-Handed Materials

The TE/TM polarization conversion characteristics of dielectric grating composed of left-handed materials for the case of plane wave oblique incidence are carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. It is indicated that complete polarization conversion between TE and TM modes can be realized using left-handed gratings. This can hardly achieve in the conventional right-handed gratings. Comparisons of polarization conversion properties between right-handed gratings and left-handed gratings are given with physical explanations. This unique merit of left-handed periodic structure is of important significance for accurate design of new millimeter wave TE/TM polarization converters.     

Propagation in a Dielectric-Loaded Parallel Plane Waveguide

A theoretical analysis of wave propagation in a parallel plane waveguide partially filled with a dielectric is performed. This transmission line is a symmetrical three-region structure consisting of two infinite parallel conducting planes with a dielectric slab of rectangular cross section between and contacting each of the planes. It has been found that TEM and TM modes cannot propagate on this structure. This investigation is concerned with TE modes, although hybrid modes can also propagate on this line. The lowest order TE mode, which is the dominant mode, has no cutoff and hence is inherently suited to extremely wide bandwidth operation. Equations have been presented for the field components, guide wavelength, cutoff criteria, power handling capabilities, wall losses, and dielectric losses as a function of the operating wavelength, waveguide dimensions, and material constants. In the case of the dominant mode, design curves covering a large range of wavelengths, dimensions, and dielectric constants are presented. For a loosely bound wave, the losses are comparable or less than those of conventional rectangular waveguide and the power handling capacity is an order of magnitude greater.     

Modes of a symmetric slab optical waveguide in birefringent media--Part 1: Optical axis not in plane of slab

We derive the eigenvalue equation and the expressions for the field distribution for the TM modes of an anisotropic symmetric slab waveguide; the TE modes are identical to the isotropic case. It is assumed that the field components do not depend on theycoordinate and that thecaxis of the uniaxial crystal lies in thex-zplane. We find that, in spite of the symmetry of the waveguide, even and odd modes do not exist because the phase fronts of the modes are tilted with respect to the waveguide axis. However, the absolute magnitude of the Hycomponent of the field has even or odd symmetry. The interesting case of an anisotropic slab waveguide with the optical axis located in the plane of the slab will be presented in Part II of this paper.     

Modes of a symmetric slab optical waveguide in birefringent media, part II: Slab with coplanar optical axis

We study the modes of a symmetric thin-film slab waveguide composed of birefringent crystalline material in the film and in the equivalent substrate and superstrate. In addition we assume that the optical axes of the uniaxial materials of film and substrate are parallel to each other and also parallel (coplanar) to the plane of the film. This simple anisotropic waveguide has interesting properties. It supports only hybrid modes but in the limit of propagation along the optical axis and at right angles to it the modes become almost of the TE and TM type. Moreover, some of the modes become leaky waves as they propagate at increasingly larger angles relative to the optical axis of the dielectric material. For guides made of materials whose ordinary refractive index nois larger than the extraordinary index ne, the extraordinary wave modes, which approximate TE modes, become leaky; and forn_{e} > n_{o}, the ordinary wave modes, which approximate TM modes, become leaky. The leakage losses are large near a "critical angle," where leakage begins to appear but may be insignificant at larger angles, measured between the optical axis and the direction of propagation.     

Analysis of Radiation From a Line Source in a Grounded Dielectric Slab Covered by a Metal Strip Grating

In this paper, we present a study of the radiation from a line source located inside a grounded dielectric slab covered by a metal strip grating. The array scanning method was applied to enable an efficient “unit cell” formulation. The numerical solution was obtained with the use of the spectral method of moments. Both TM and TE cases were solved. The effects of the geometrical parameters on the propagation of guided modes and their excitation are studied.      

Monte Carlo simulations of large-scale one-dimensional randomrough-surface scattering at near-grazing incidence: Penetrable case

Scattering from dielectric one-dimensional (1-D) random rough surfaces at near grazing incidence is studied for both TE and TM cases. To obtain accurate results at incidence angles of 80°-85°, we use long surface lengths of up to 1000 wavelengths. Numerical results are illustrated for dielectric surfaces corresponding to soil surfaces with various moisture contents. Results indicate that TM backscattering is much larger than that of TE backscattering. The ratio of TM to TE backscattering increases as a function of soil moisture and can be used as an indicator of soil moisture in remote sensing applications. However, the ratio of TM to TE backscattering is much lower than that predicted by the small perturbation method. To facilitate computation of scattering by such long surfaces, the previously developed banded-matrix iteration approach/canonical grid method (BMIA/CG) has been extended to dielectric surfaces. The numerical algorithm consists of translating the nonnear-field interaction to a flat surface and the interaction subsequently calculated by fast Fourier transform (FFT)     

含单负材料对称三层平板波导的模式特性

由电磁场的波动方程和边界条件建立了单负材料作为芯层的对称三层平板波导的模式本征方程,用图解法研究其色散特性。研究发现,单负介质波导不支持快波的传播,只支持表面波的传播。在负磁材料平板波导中只存在TE表面模,不存在TM表面模。分析了在负磁材料平板波导中TE模受磁导率的比值-μ2／μ1和波导参数的影响,给出了横向场分布图。在-μ2/μ1〈1时,偶对称只有TE0表面模存在,奇对称只有TE1表面模存在,高阶模式并不存在,且两种模式都没有低频截止;-μ2/μ1〉1时,TE1表面模始终不出现;TE0模的存在与否和波导参数有关,在一定条件下TE0模可出现双模并存。给出的结果可望对表面波器件的设计提供理论基础。     

Propagation of TE Modes in Dielectric Loaded Waveguides

The propagation of TE/sub no/ modes in rectangular wave-guides that contain two dielectric slabs parallel to the narrow wall and extending over the full height of the guide is investigated. Waveguide and dielectric are assumed to be lossless and infinitely long. Apart from these restrictions, the dielectric slabs may have arbitrary thickness, position, and dielectric constant. The analysis is restricted to TE/sub no/ modes with the E-field parallel to the narrow guidewall. The guide containing only one dielectric slab is covered by this analysis. The even modes n = 2, 4, 6, . . . of the guide with two slabs correspond to the odd modes n' = n/2 = 1, 2, 3, . . . of the guide with one slab half the width of the guide with two slabs. For six relative dielectric constants (/spl epsilon/= 2.25, 4.00, 9.00, 12.25, 16.00, 25.00) the cutoff frequencies for TE 10, 20, 30, 40, 60 modes and the normalized propagation constants for TE 10 and TE 20 modes between their respective cutoff frequencies and a frequency slightly above the second- and fourth-order mode cutoff frequency for the empty guide, respectively, have been computed for a large range of slab thicknesses and slab positions. Selected results are presented graphically. These results are discussed. The parametric dependence of field distributions, of normalized characteristic impedances, of the ratio of cutoff frequencies (fractional bandwidth), and of the ratio of magnetic field components (ellipticity) are illustrated.     

Finite-element formalism for nonlinear slab-guided waves

A unified computer-aided numerical approach, based on the finite-element method, is developed for analyzing optical waves guided by dielectric slab waveguiding structures with arbitrary nonlinear media. In the formulations, both TE and TM polarizations are considered. For the TM case, the biaxial nature of nonlinear refractive index is considered without any approximation. Numerical results are presented for nonlinear TE and TM waves propagating in symmetric slab waveguides. The dependence of dispersion relations on the refractive-index profile of the film is examined     

Variational Treatment of the Diffraction at the Facet of d.h. Lasers and of Dielectric Millimeter Wave Antennas

This paper presents an accurate variational treatment of the diffraction of TE and TM waves by an abrupt transverse discontinuity in a dielectric waveguide, such as the mirror of a double heterostructure (d.h.) injection laser, or the end plane of a dielectric slab antenna for millimeter waves, under the assumption of small aspect ratio. A matrix representation of the Green's function is derived analytically, in the limit of small efective frequency, for the TE case. For the TM case, the complication introduced by the discontinuity of the transverse electric field across the dielectric interface is discussed in detail. The numerical examples refer to the d.h. laser configuration. Both transverse directions (perpendicular as well as parallel) to the junction are studied. The effect of mode coupling at the mirror of a LOC laser as well as the effect of an antireflection coating are investigated.     

Exact solutions for TM modes in graded index slab waveguides

Three continuous profiles for the dielectric constant are derived, which allow exact solutions of the vector wave equation, including all terms in the gradient of the profile, for both TE and TM modes on slab waveguides. The dielectric constant has been assumed to be a scalar quantity; i.e., the medium is isotropic.     

对称单负材料平面波导的波导模

基于经典电磁理论建立了芯层为单负材料的对称三层平板波导的导波方程,采用图解法研究了该波导中的TE和TM波导模,分析了TE波导模和TM波导模会受波导参数μ1/μ2和R的影响,给出TE模和TM模解的横向场分布图.结果显示,在单负材料的对称三层平板波导中只存在慢波导模,TE慢波模只能在磁负材料中传播,TM慢波模只能在电负材料...     

A SIMPLE SOLUTION FOR MULTILAYER METALLIC OPTICAL WAVEGUIDES

A simple solution for a multilayer metallic optical waveguide by transforming it intoan equivalent three-layer slab waveguide is presented. The dispersion relation of the equivalentthree-layer slab waveguide is solved by using a simple iterative formula. This method itself isexact and can approach any accuracy desired. Moreover, the numerical results for four-layer andfive-layer structures show that the second-order solution is also accurate enough. It is simple andhas the same form of expressions for TE and TM modes and for different layer structures.     

Spontaneous emission coupling to radiation and guided modes ofplanar waveguide structures

A general analysis of spontaneous emission in the vicinity of a symmetric slab dielectric waveguide is presented using explicit energy-normalized functions for the complete set of bound and radiating TE and TM modes. Expressions for the spontaneous emission rates are derived for each mode type, and calculated results are presented illustrating the emission behavior as a function of the position of the radiating atom, for various slab waveguides. The model is used to analyze the spontaneous emission coupling efficiency to guided modes in planar erbium-doped amplifier structures. Spontaneous emission factors for the TE and TM modes are calculated for the cases of erbium doping of the core and of the cladding