Propagation Constants Of Waves Research Articles

Fast and Accurate Transient Analysis of Buried Wires and its Applications

An improved finite difference time-domain (FDTD) method based on the telegraph equations of transmission lines is proposed. The original time-domain simulation method that resembles the well-established FDTD scheme based on the Maxwell's equations has been used in this paper to tackle the modeling problems of buried and overhead transmission lines. In this paper, a group of time domain responses of the ground impedance or ground admittance can be extracted analytically by means of a correlation between the ground impedance and the ground admittance. Thanks to the analytical technique, the accuracy of this time-domain solution is improved significantly. As a result, the application of this time-domain algorithm can be greatly expanded beyond the modeling of common transmission lines. By combining with the shunt and series connection difference equations, the method can be used to analyze an entire buried grounding network. Because the correlation between the ground impedance and the ground admittance is related to the propagation constant of electromagnetic waves, the analytical technique makes the propagation velocity unchanged during the iterative calculation. Therefore, the improved FDTD method allows the grounding network to be analyzed more accurately and efficiently.

Existence of Optical Vortices

Optical vortices arise as phase singularities of the light fields and are of central interest in modern optical physics. In this paper, some existence theorems are established for stationary vortex wave solutions of a general class of nonlinear Schrödinger equations. There are two types of results. The first type concerns the existence of positive-radial-profile solutions, which are obtained through a constrained minimization approach. The second type addresses the existence of saddlepoint solutions through a mountain-pass theorem or min-max method so that the wave propagation constant may be arbitrarily prescribed in an open interval. Furthermore, some explicit estimates for the lower bound and sign of the wave propagation constant with respect to the light beam power and vortex winding number are also derived for the first type of solution.

Wave Propagation in Dielectric Slab Waveguide with two Different Cladding Materials.

In this study the Ku ــband microwave with a frequencies of (12- 18) GHz propagation in dielectric materials InGaAsP( refractive index n1=3.39) with two different claddings, air(n2=1) and polyacrylate(n2=1.5) , was investigated. Using the cladding polyacrylate gives better results.The graphical and numerical results of the behavior of electromagnetic wave propagation along Z - direction in dielectric slab waveguide in the two cases of cladding were investigated with the aid of MATLAB program. The graphical and numerical results coincide. The modes of propagation have been analyzed and all parameters have been given. The values of different parameters as cutoff wave number, cutoff frequency, cutoff thickness , propagation constant, and transmission of electromagnetic wave have been calculated. The transmission of the microwave depends on the slab thickness and the frequencies applied and it has been found to varied from 75% to 100%. The reflection amplitude inside the slab is not effected when the angle of the incident wave is less than the critical angle, while it increased rapidly as the angle increased higher than the critical angle.

Propagation of elastic wave in nanoporous material with distributed cylindrical nanoholes

The effective propagation constants of plane longitudinal and shear waves in nanoporous material with random distributed parallel cylindrical nanoholes are studied. The surface elastic theory is used to consider the surface stress effects and to derive the nontraditional boundary condition on the surface of nanoholes. The plane wave expansion method is used to obtain the scattering waves from the single nanohole. The multiple scattering effects are taken into consideration by summing the scattered waves from all scatterers and performing the configuration averaging of random distributed scatterers. The effective propagation constants of coherent waves along with the associated dynamic effective elastic modulus are numerically evaluated. The influences of surface stress are discussed based on the numerical results.

A New Look at Azimuthal Wave Propagation Constants of an n-Layered Dielectric Coated PEC Cylinder

A method for determining the azimuthal wave propagation constants supported by an n-layered dielectric coated PEC cylinder is presented. The method, based on a Green's function described in <citerefgrp xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><citeref refid="ref1"/> </citerefgrp> , is designed to optimally handle layered cylinders where the number of layers is extremely large as might be encountered in structures designed using transformational optics. The method is also tractable for any stratification profile without the need for individual layer analysis. We implement a recently developed numerical method to calculate Bessel functions of complex order and argument. Our method is verified by comparison with previously published results. We also present new results for a 5-layer case demonstrating self consistency and improved accuracy over published methods. Finally, to illustrate the method's benefits, we present a brief analysis of two multilayer structures; a multilayer variation of the coated cylinder presented in <citerefgrp xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <citeref refid="ref2"/></citerefgrp> and an example of a 7-layer case that approximates a material parameter gradient.

Nonreciprocity in single-mode fiber coil induced by orthogonal magnetic field

We investigated the nonreciprocity induced by an orthogonal magnetic field (OMF) in a single-mode fiber coil and expressions for the propagation constant of light waves in the bent fiber are deduced. Coils with different radiuses are put into depolarized interferometric fiber optic gyroscopes (D-IFOGs) for experimental verification. Theories, simulations and experimental results show that the OMF induced nonreciprocal phase error is closely related to the bending radius and the generated magnetic drift in D-IFOGs is linear to the amplitude of the OMF.

Effect of Sand and Dust Storms on Microwave Propagation

The general formulas of the wave propagation constant through sand and dust storms are developed in this paper, which is based on the forward scattering amplitude of particle under the Rayleigh approximation. Expressions for attenuation and phase shift coefficients for a medium with sand and dust particles are derived in terms of visibility and frequency. Computations show that the predicted values from the given mathematical expressions are an excellent agreement with the values by Goldhirsh's formula. Expressions for the differential attenuation and differential phase shift are also derived for both vertical and horizontal polarizations. Obtained results of the attenuation of horizontal and vertical polarization wave are compared with those obtained by Wenyan 's formula and Ghobriel 's formula, respectively. It is found that the attenuation obtained by our proposed formula and Ghobrial 's formula show close agreement. The cross-polar discrimination is calculated and discussed.

Stable algorithm for the computation of the electromagnetic field distribution of eigenmodes of periodic diffraction structures

In the present work, a stable algorithm for the calculation of the electromagnetic field distributions of the eigenmodes of one-dimensional diffraction gratings is presented. The proposed approach is based on the method for the computation of the propagation constants of Bloch waves of such structures previously presented by Cao et al.[J. Opt. Soc. Am. A 19, 335 (2002)] and uses a modified S-matrix algorithm to ensure numerical stability.

The effective propagation constants of SH wave in composites reinforced by dispersive parallel nanofibers

In the present paper, the effective propagation constants of elastic SH waves in composites with randomly distributed parallel cylindrical nanofibers are studied. The surface stress effects are considered based on the surface elasticity theory and non-classical interfacial conditions between the nanofiber and the host are derived. The scattering waves from individual nanofibers embedded in an infinite elastic host are obtained by the plane wave expansion method. The scattering waves from all fibers are summed up to obtain the multiple scattering waves. The interactions among random dispersive nanofibers are taken into account by the effective field approximation. The effective propagation constants are obtained by the configurational average of the multiple scattering waves. The effective speed and attenuation of the averaged wave and the associated dynamical effective shear modulus of composites are numerically calculated. Based on the numerical results, the size effects of the nanofibers on the effective propagation constants and the effective modulus are discussed.

Complex waves on periodic arrays of lossy and lossless permeable spheres: 1. Theory

This is the first part of a two‐part series dealing with complex dipolar waves propagating along the axes of 1D, 2D, and 3D infinite periodic arrays of small lossless and lossy permeable spheres. The theory is presented in this paper and numerical results are presented by Shore and Yaghjian (2012). The focus is on the dispersion (k–β) equations relating the array propagation constant, β, to the free‐space wave number,k, for dipolar complex waves. The k–β equation for the complex propagation constants of a given array is obtained from the corresponding equation previously obtained for the real propagation constants by rewriting the real propagation dispersion equation in a form that can be analytically continued into the complex β plane. This equation reduces correctly to the real β dispersion equation and enables complex values of β to be found as a function of the array element parameters. By allowing for all the possible branches of the multivalued homogeneous dispersion equation analytically continued into the complex βplane, the propagation constants of all the improper as well as proper complex waves supported by the 1D, 2D, and 3D arrays are found from the homogeneous solutions for these arrays. Green's functions for external sources are not required to find the propagation constants of the complex waves supported by the arrays. For 3D arrays, in certain frequency ranges, it is possible to regard the arrays as media characterized by bulk or effective permittivities and permeabilities. Expressions for these bulk parameters, more accurate than the Clausius‐Mossotti expressions, are obtained from quantities readily available in the solutions of the dispersion equations.

An empirical modelling of porous sound absorbing materials made of recycled foam

Polyurethane foam waste is one of the residues of the manufacturing processes in textile industry, the disposal of which is becoming a severe environmental problem. In this paper the sound absorption properties of different materials developed from ground polyurethane foam waste are studied. Because these recycled materials exhibit good sound absorbing properties they are viable alternatives to conventional materials for practical applications. Experimental measures have been carried out to determine the characteristic wave impedance and propagation constant of these materials. Modelling of the acoustic behaviour has been done using the Dunn and Davern model and Voronina model. The first model presents deviations in the results so the experimental results have been used to report corrections to the empirical model. The Voronina model has been applied to verify that it serves to model the behaviour of these kinds of recycled materials. Both models converge and present acceptable results.

Excitation of Broadband Surface Plasmons with Dye Molecules

Rhodamine B and Rhodamine 6G molecules were doped in polymethyl methacrylate solution. Then a silver film on the glass substrate was spin coated with the mixed solution to get a multilayer film. Under the irradiation of a 532-nm green laser, broadband surface plasmons (SPs) on the silver film were generated due to the coupling between the broadband fluorescence and the SP modes allowed in the multilayer film. From the back focal plane image of a leakage radiation microscopy, propagation constants of SP waves at different wavelengths were derived. Numerical calculations were also carried out and were consistent with the experimental results.

Terahertz and Infrared Surface Wave Beams and Pulses on Gyrotropic, Nonlinear and Metamaterial Interfaces

This work is devoted to theoretical study of surface plasmon polariton propagation on metal or metamaterial – dielectric interfaces where media can possess optical or magnetooptical activity or cubic nonlinearity. On the interface of gyrotropic media surface wave changes its polarization and profile as well as in case of interface of media with cubic nonlinearity. Surface wave propagation constant can be modified by magnetization leading to magnetooptical intensity effect. The properties of plasmons in gratings are also considered including excitation, dispersion and existence of various types of modes. The theory of surface wave and pulsed beam diffraction in gyrotropic, nonlinear and layered media is developed. We also present waveguide for surface waves based on layered metamaterial – dielectric interfaces suppressing diffraction spreading.

Effects of Charged Particles Size Distribution on Microwave Propagation in Sandstorms

A general formula of the wave propagation constant through sandstorms for any distribution is developed in this paper, which is based on the forward scattering amplitude of the charged sand particle under the Rayleigh approximation and could be dealt with the case of passing through the charged particles. It is found that the microwave propagation mainly depends on the value of I 3 /I 2 and I 4 /I 2 relating to the particle size distribution. A simple relationship is shown between attenuation A and ' I 3 /I 2 , I 4 /I 2 ' of the sandstorms. Attenuation due to charged sand particles is calculated for four distributions namely Uniform, Exponential, Rayleigh and Lognormal. Results are presented, and the effect of the distributions is discussed.

Surface plasmon-polariton waves in optically active media

We investigate surface plasmon polariton waves on the semi-infinite and multilayered interfaces of metals or metamaterials with optically active dielectrics. Such surface waves consist of two partial components with different polarization and localization. Propagation constant, localization coefficients and polarization of surface waves were calculated in the linear approximation that can be used in the cases of weak gyrotropy. Plasmon polariton waves on the interfaces with stronger gyrotropy were investigated numerically. We found out that there is a critical value of gyrotropic coefficient above which there are no localized surface waves on the interface.

Using Stress Wave Based Technology for Wood Material Nondestructive Testing

Stress wave based technology has its special advantages in the field of wood nondestructive testing and quality evaluation. To analysis the propagating properties of stress wave in the wood material, a transmitting model in anisotropic material was introduced in rectangular and cylindrical polar coordinate system. The relationship between stress wave propagation and elastic constants was shown. The propagating of stress wave in wood material and the possible solutions with different parameters were studied. The transmitting character of stress wave in symmetry planes was analyzed, and the elastic constants of woods were used to compute the stress wave propagation in wood material.

ELECTROMAGNETIC WAVES OF A PLANAR LAYERED METAL-DIELECTRIC STRUCTURE

The dispersion relation for propagation and attenuation constants of electromagnetic waves which are supported by a metal film placed on a substrate and covered by a thin dielectric layer is studied numerically in visible and infrared wavelength ranges.

Calculation of the propagation constants and fields of polarized electromagnetic TM waves in a nonlinear anisotropic layer

Propagation of polarized electromagnetic TM waves through a nonlinear homogeneous nonmagnetic dielectric layer located between two homogeneous isotropic half-spaces is considered. The dispersion equation is derived for the propagation constants (eigenvalues) of waves in the layer. The propagation constants for nonlinear and linear media in the layer are compared. The propagation constants and fields (eigenfunctions) are calculated.

LOWER FREQUENCY LIMIT OF CARBON NANOTUBE ANTENNA

Carbon nanotubes are characterized by slow wave propagation and high characteristic impedance due to the additional kinetic inductive efiect. This slow wave property can be used to introduce resonant dipole antennas with dimensions much smaller than traditional half-wavelength dipole in Terahertz band. However, this property has less efiect at lower frequency bands. This paper introduces the physical interpretation of this property based on the relation between the resonance frequency and the surface wave propagation constant on a carbon nanotube. This surface wave propagation is found to be characterized by high attenuation coe-cient at low frequency bands which limits using carbon nanotube as an antenna structure at these frequencies.

The role of leaky plasmon waves in the directive beaming of light through a subwavelength aperture

We show that the enhanced directivity phenomenon for light passing through a subwavelength aperture in a silver film with corrugations on the exit face, is due to a leaky wave that decays exponentially from the aperture. We show quantitatively that the field along the interface of the silver film is dominated by the leaky wave, and that the radiation of the leaky wave, supported by the periodic structure, yields the directive beam. The leaky wave propagation and attenuation constants parameterize the physical radiation mechanism, and provide important design information for optimizing the structure. Maximum directivity occurs when the phase and attenuation constants are approximately equal.