摘要:

Polarization dynamics of the vector solitons in a birefringent single-mode optical fibre in the framework of a system of coupled nonlinear Schrödinger equations with oscillating terms has been studied, and a condition for their stability has been deduced. This study should evoke considerable interest because of its potential applications in optical logic devices.

ISSN:0950-0340    

DOI:10.1080/09500349608232719

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The phase properties of the squeezed thermal states have been studied by evaluating the expression for the phase probability distribution and the phase variance in the weak squeezing limit.

ISSN:0950-0340    

DOI:10.1080/09500349608232720

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The travelling-wave second-harmonic generation can be studied in the cases of co- and contradirectional propagations provided that in the contradirectional case an approximative Heisenberg picture is accepted. Selected statistics makes evident the squeezing property and the Kerr-type behaviour in the fundamental mode.

ISSN:0950-0340    

DOI:10.1080/09500349608232721

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

New inverse method is proposed to determine the four-layer leaky waveguide parameters from the set of experimentally measured effective refractive indices. The sensitivity of each parameter to the measurement error in effective refractive indices is investigated. An algorithm is proposed to find the best-fit values of the waveguide parameters.

ISSN:0950-0340    

DOI:10.1080/09500349608232722

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An important problem in optics involves the computation of the field amplitude in the Fresnel region of a circular lens. When the observation point lines in the image plane, it is well known that the field can be written in closed form in terms of Bessel functions, i.e. the Airy pattern. In this paper, it is shown that away from the image plane the field can be expressed in terms of incomplete Weber integrals. This closed-form representation is much more accurate than the commonly used technique involving fast Fourier transforms (FFTs). This is demonstrated by comparing the closed-form results with those produced by an FFT. The closed-form solution is used to study the resolution of two point sources under the assumption that the observation plane is misaligned from the image plane.

ISSN:0950-0340    

DOI:10.1080/09500349608232723

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We deal with the determination of the profile of a stratified medium with the absolute intensities of the specularly reflected field as input. The measurements can be performed at different angles of incidence at a fixed wavelength or at various wavelengths if the medium is dispersionless. The forward problem is linearized to allow one to use a matrix formulation of the discretized direct operator and the inverse problem is solved by an iterative process. Since the problem belongs to the class of the so-called ill-posed or ill-conditioned problems, a regularization method based on Tikhonov's method of the stabilizing functional is implemented. We present a numerical test in the X-ray spectral range where the method offers a considerable field of application for structural analysis.

ISSN:0950-0340    

DOI:10.1080/09500349608232724

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The optical dielectric function of silver is measured by excitation of surface plasmon-polaritons on a silver-covered silica grating for a range of wavelengths in the visible region of the spectrum. By exciting the surface plasmon-polariton at the grating/silver interface the silver is protected from sulphidization and contamination. Comparison of angle-dependent reflectivities with grating modelling theory gives both the real and imaginary parts of the dielectric function of the silver. The results compare very favourably with those obtained by other workers using more conventional methods for samples held in an ultra-high vacuum or with protected interfaces.

ISSN:0950-0340    

DOI:10.1080/09500349608232725

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We show that interaction of modes having different wave-numbers in a Kerr-slice/feedback-mirror type optical system with Fourier filter in the optical feedback leads to formation of new types of patterns. Results of numerical simulations are presented.

ISSN:0950-0340    

DOI:10.1080/09500349608232726

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The reflectivities and transmissions of the first two Laguerre-Gauss modes incident on a Fabry-Perot interferometer are calculated and compared. It is shown that, dependent on beam-waist size, the Fabry-Perot interferometer can behave as a spatial filter. For example, the reflectivity of the TEM00mode can be larger than for the TEM01mode. This could allow for fundamental mode selection in a laser without resorting to an intracavity aperture.

ISSN:0950-0340    

DOI:10.1080/09500349608232727

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In the inverse problems of Fourier synthesis encountered in aperture synthesis, the data are complex quantities corresponding to an irregular sampling of the Fourier transform of some non-negative object function. CLEAN is a deconvolution method which is intensively used in this context. This series of two papers is meant to provide, as an alternative to CLEAN, a well-formulated deterministic method, in which the propagation of errors is under control. The method introduced in part I is referred to as FIRST or WIPE: FIRST for the principles (Fourier Interpolation and Reconstruction via Shannon-type Techniques), and WIPE for the corresponding deconvolution method (WIPE is reminiscent of CLEAN). The main purpose of part II is to complete the general framework presented in part I. In particular, we present a new method for computing the dusty map and the dirty beam. The related techniques of fast Fourier sampling and gridding are thoroughly analysed. We then explicitly describe the imaging kernel of WIPE by presenting the basic algorithm, the role of the Krylov spaces in the control of its robustness and the calculation of the image reconstruction error bars. Among the regularization parameters appearing in the definition of the objective functional of FIRST, those related to the choice of the object representation space play an essential role. This is why an entire section is devoted to the methods that can be devised and implemented for constructing this space, in a global manner or step by step, interactively or automatically. All the technical developments presented in this paper are illustrated with the aid of appropriate simulations, so that the main aspects of FIRST and WIPE can be understood in a concrete manner. The methodology underlying FIRST can be applied to more complex experimental situations such as those encountered, for example, in mosaic image reconstruction, multifrequency Fourier synthesis and in multiresolution aperture synthesis. This is outlined in the concluding comments.

ISSN:0950-0340    

DOI:10.1080/09500349608232728

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor