摘要:

We propose an alternative formulation of the finite-difference beam propagation method based on the volume integral method. The usually employed Crank-Nicholson formulation can be obtained by numerically integrating the wave equation in the Fresnel approximation along the propagation direction using the trapezoidal rule, with the transversal operator previously discretized. In our method, we first integrate the wave equation in a cell of the computing grid, and next use finite difference approximations for the partial derivatives to complete the discretization of the problem. All the results are obtained for transversal electric fields in two-dimensional guiding structures (planar waveguides) for the sake of simplicity, although the method can be applied easily to more general situations. The method is assessed, and the results, when compared with those obtained from the traditional formulation, show better accuracy even with a lower number of points in the computation grid.

ISSN:0950-0340    

DOI:10.1080/09500349514550461

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In depositing crystalline thin films, anisotropy may be induced by the texture structure of the film. Generally one of the principal axes of this anisotropy is in the direction of columnar growth, which may be neither normal nor parallel to the film surface. In this paper we have developed a general method for characterizing thin films with this kind of anisotropy. Propagation of plane waves in media with the above mentioned crystalline structure has been studied. The reflectance and transmittance of a plane wave from the films with the structure-induced anisotropy have been calculated. By comparing calculations with measurements, we could determine optical properties and thicknesses of the films with the columnar-structure-induced anisotropy.

ISSN:0950-0340    

DOI:10.1080/09500349514550471

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The finely stratified sphere model is used to calculate light scattered from homogeneous spheres covered by a film with a variable refractive index. The influence of an inhomogeneous film covering a homogeneous sphere depends on the thickness and the profile of the refractive index of the film. If the film is very thin, the sphere can be considered to be homogeneous and the Mie theory can still be used. Positions of the morphology-dependent resonances on a extinction efficiency against size parameter spectrum depend on the average value of the refractive index of the region of surface wave resonance.

ISSN:0950-0340    

DOI:10.1080/09500349514550481

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

By invoking an exactly solvable model as the generalization of the Jaynes-Cummings model, the influence of spatial motion of atomic centre on the dynamics of a single-mode cavity-two-level atom system are studied for various initial conditions. These investigations show that the Doppler effect exercised by the motion of atom in a locally inhomogeneous cavity field can lead to the phenomenon of oscillation collapse and revival in the transition probability and the atomic population inversion.

ISSN:0950-0340    

DOI:10.1080/09500349514550491

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Starting from the generalized Huygens-Fresnel diffraction integral, we study the intensity distribution of a Gaussian Schell-model (GSM) beam diffracted at an aperture lens. A great number of numerical calculations have been performed to illustrate the focused field characteristics. Isophote diagrams are given for systems of different Fresnel numbers, which focus GSM beams, and the related analysis is presented.

ISSN:0950-0340    

DOI:10.1080/09500349514550501

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Starting from the experimental observation and the theoretical prediction that different types of highly birefringent (Hi-Bi) fibres suppress different LP11polarization modes, a generalized theoretical analysis of LP01–LP11intermodal interference in Hi-Bi bimodal optical fibres is presented. Differential attenuation for each of the four LP11polarization modes is assumed and, on this basis, spatial Stokes parameters accounting for intermodal interference effects are derived. The most important particular cases of elliptical-core, bow-tie and PANDA-type fibres are considered. The application to combined polarimetric and polarization sensitive intermodal sensors, as well as to simultaneous multiparameter sensing in Hi-Bi fibres is commented upon.

ISSN:0950-0340    

DOI:10.1080/09500349514550511

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A helium-neon laser operating in two or more axial modes generates beat signals in the ultra-high frequency (UHF) range at a photodetector. An analysis of earlier data obtained at very low light levels shows that such UHF beats can be observed even when the mean time interval between the arrival of successive photons at the photodetector is greater than the period of the beat. This is because the beat is actually a sinusoidal modulation of a random carrier.

ISSN:0950-0340    

DOI:10.1080/09500349514550521

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Squeezing in the Jaynes-Cummings model with a two-level atom initially in a coherent superposition of its ground and excited states and coupled to a thermal field is considered, and the bounds on squeezing are determined.

ISSN:0950-0340    

DOI:10.1080/09500349514550531

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

It is shown that, under rather general conditions, a single discrete (ground) state being excited to a continuum with periodic structure will experience a periodic disruption in the time-evolution of its population and that, in the initial interval before the first disruption, this evolution always follows that of the Weisskopf-Wigner result. A general formula for the ground-state amplitude is found in terms of the Fourier coefficients of the coupling, and special cases are considered.

ISSN:0950-0340    

DOI:10.1080/09500349514550541

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The properties of states generated by the application of the two-mode squeeze operator to the pair coherent states are studied. These states are the two-mode analogues of the single-mode squeezed states generated by the application of the single-mode squeeze operator to an ordinary coherent state. In the present case there are correlations between the modes and strong non-classical properties are to be expected. We study the statistical properties of the photon number distributions, squeezing, violations of the Cauchy-Schwartz inequality, quasiprobability distributions and the phase distributions.

ISSN:0950-0340    

DOI:10.1080/09500349514550551

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor