摘要:

We outline the program of a. functional approach to nonlinear electromagnetic wave propagation and scattering. The proposed approach is general and systematic and the final results are in analytic form. Most of the computational burden can be left to computer algebra. We stress that the proposed approach waits for the next generation of computers to prove practically valuable.

ISSN:0272-6343    

DOI:10.1080/02726349108908282

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Accurate orientational probability distribution functions are derived which describe the dynamical behavior of permanent and induced dipole moments in an external field. The method involves a transformation of the Smoluchowski equation into a Schrödinger–like equation with real eigenvalues. The method is applied here for the first time to the case of suspensions of large noninteracting anisotropic particles which are of interest as artificial Kerr materials for nonlinear electrooptical applications. A matrix presentation is made in which the effects of any combination of permanent and induced dipole moments are described by a single matrix. The eigenfunctions and eigenvalues of this matrix when specific material parameters are substituted provide a Fourier cosine series expansion for the angular distribution function under conditions of cylindrical symmetry which is valid for aligning fields of any magnitude. The only restriction is that larger fields require larger matrices for more accurate results. The method is used to analyze the competition between the aligning contributions of permanent and induced dipole moments and the effects of permanent dipole moment and field magnitude on alignment times are obtained.

ISSN:0272-6343    

DOI:10.1080/02726349108908283

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

IN THIS PAPER A MODEL FOR OPTICAL BISTABILITY IN A RIDGE WAVEGUIDE FABRY-PEROT RESONATOR IS PRESENTED. THE NON-LINEARITY IS DUE TO A MULTIPLE QUANTUM WELL STRUCTURE INSERTED INTO THE RESONATOR. NEAR THE EXCITONIC RESONANCE A BISTABLE BEHAVIOUR HAS BEEN FOUND, AS SHOWN BY EXAMPLES OF STEADY-STATE RESPONSE.

ISSN:0272-6343    

DOI:10.1080/02726349108908284

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We consider the kinematic problem of one-dimensional space-charge wave propagation on a thin (surface current) electron beam in an axially uniform lossless structure. A general nonlinear integral equation describing the wave propagation is developed; the kernel of the integral equation is the Green's function for the waveguiding structure. In the small-signal limit, the integral equation becomes linear and homogeneous and yields the linear dispersion relation through the Fourier transform. The general formulation is applied to an annular beam in a perfectly conducting circular waveguide. It is shown that the nonlinear integral equation can be reduced to a nonlinear differential equation through the use of an approximate Green's function. With further approximation, the differential equation yields onoidal wave solutions, including solitary-wave solutions in appropriate limiting cases. Approximate analytical and “exact” numerical results are presented and compared.

ISSN:0272-6343    

DOI:10.1080/02726349108908285

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This paper deals with electromagnetic scattering In the presence of nonlinear dielectric objects. The Introduction of equivalent source terms makes it possible to describe the electromagnetic field by an integral formalism which takes into account nonlinear effects by solving inhomogeneous wave equations through specific dyadic Green functions. Examples of application to nonlinear scattering objects, In free space and In a rectangular waveguide, are considered. The related integral problems are reduced to nonlinear systems of algebraic equations. Results of some computer simulations Involving simple scattering objects are also reported.

ISSN:0272-6343    

DOI:10.1080/02726349108908286

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The general solution of the scattering of harmonic signals, by a medium which has nonlinear constitutive relations, contains higher harmonics. The scattering amplitude consists of the linear component and additional correction terms that depend on the amplitude of the incident wave. In this paper, we examine the effects of nonlinearities on the field components and on the radar cross section at the second and third harmonics.

ISSN:0272-6343    

DOI:10.1080/02726349108908287

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A quasi-finite element method for calculation of static fields in media with hysteresis is presented in this paper. The proposed method utilizes vector Preisach hysteresis model to describe the material behavior. Time-stepping technique is employed in which the evolution of the electromagnetic system is traced to compute the field history as well as the current value of the field self-consistently. At every step in this technique a boundary value problem is solved by using coupled boundary-volume Galerkin's forms. In this formulation, the solution within the material medium is approximated in terms of finite element basis funtions, while the solution outside the material medium is approximated in terms of harmonic functions. An iterative technique for the solution of the resulting set of nonlinear equations is described. The proposed method is demonstrated on two dimensional electrostatic problems.

ISSN:0272-6343    

DOI:10.1080/02726349108908288

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We consider a generalized nonlinear Schrödinger equation: iqt + qxx + 2klql2q - ikb(lql2q)x = 0 at various initial conditions. For the purpose of practical applications in optics, we study the following initial value problems: decay of the sech-pulses; dynamics of randomly modulated solitons, and evolution of nonsoliton random pulses. The first of the above problems is solved exactly. Conditions of the sech-pulse decay are stated. For the solution of the second problem, a perturbation theory is developed. Statistical characteristics of both a soliton under the Gaussian initial fluctuations, and noise generated in the system are obtained. Soliton parameters are distributed according to the Gaussian law. The relationship between correlation characteristics of the noise and those of the linear beam in the problem of the Fraunhofer diffraction on a gap is established. The asymptotic formula describing a nonsoliton solution at sufficiently large times is stated. The Fokker-Plank equation for probability density of the amplitude and phase of the reflection coefficient is derived. The drift velocity of the mean peak intensity is calculated. A case of weakly nonlinear pulse propagation is considered in the framework of a perturbation theory. All results are compared with those obtained earlier for the nonlinear Schrödinger equation.

ISSN:0272-6343    

DOI:10.1080/02726349108908289

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor