摘要:

When coherent light impinges on a rough diffuser with an angle of incidence different from zero, the maximum of the mean scattered intensity moves away from the direction that would be given by the Snell law if the interface were flat. This phenomenon is known asnon-refractive effect. We report here that we have found experimentally that the same effect occurs for white light and that a simple geometrical model accounts for it.

ISSN:0950-0340    

DOI:10.1080/09500349808231907

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new nonperturbative regime of radiation-matter interaction is examined by considering atoms interacting with fields in exceptionally high quality cavities. A general framework for the study of such systems is presented. The new features that arise from the strong coupling to the cavity mode are thoroughly analysed and the underlying physics and experiments are reviewed. The nonlinear processes are shown to be very sensitive to the sample size.

ISSN:0950-0340    

DOI:10.1080/09500349808231908

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The subject of electromagnetically induced transparency (EIT) is reviewed in this paper. Emphasis is placed on the experimental work reported in this field since 1990. Theoretical work is also covered, although it is not intended to review all the very numerous recent theoretical treatments on this topic. The basic physical ideas behind EIT are elucidated. The relation of EIT to other processes involving laser-induced atomic coherence, such as coherent population trapping, coherent adiabatic population transfer and lasing without inversion, is discussed. Experimental work is described covering the following topics: EIT with pulsed and continuous-wave sources, lasing without inversion, pulse propagation in a laser dressed medium and EIT in nonlinear optical processes. A full set of references and a bibliography are included.

ISSN:0950-0340    

DOI:10.1080/09500349808231909

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In a fibre-optic interferometer, when the frequency linewidth of the light source is larger than a certain value, the influence of optical fibre dispersion should be considered. In this paper, considering the dispersion effect, we present a theoretical analysis of the output noise power spectrum of the fibre-optic interferometer induced by the random phase noise of semiconductor lasers. The analysis focuses on the noise power spectrum influenced by the first-order dispersion of the single-mode optical fibre. The closed expressions of output noise characteristics are derived. The formulations obtained in this paper can be applied to both a dispersion and a non-dispersion fibre-optic interferometer or optical interferometer.

ISSN:0950-0340    

DOI:10.1080/09500349808231910

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The diffraction of an electromagnetic wave by a perfectly conducting strip in a bi-isotropic medium is studied. The problem is solved using integral transforms, the Wiener-Hopf technique and asymptotic methods. The diffracted field is found to be the sum of the fields produced by the two edges of the strip and an interaction field.

ISSN:0950-0340    

DOI:10.1080/09500349808231911

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The signal level in a fibre-optical confocal scanning microscope using step-index profile fibres is investigated. The dependence of the signal level on the fibre parameterVis studied. Two different systems are investigated. For the first case of a system employing a point source and a fibre for collection, the maximum value of signal level for a givenVis given. The signal level for a second arrangement, when the system uses a fibre for both illumination and collection, is also studied. It is found that, in both cases, optimum overall performance is achieved for large values ofV.

ISSN:0950-0340    

DOI:10.1080/09500349808231912

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

On the basis of the modal theory of coherence, we study partially coherent sources whose modes belong to the class of Laguerre-Gauss functions for which the Laguerre polynomial has zero order. These modes present a phase profile with a helicoidal structure, which is responsible for notable phenomena, such as the propagation of optical vortices, beam twisting, and the presence of dislocations in interference patterns. By suitably choosing the eigenvalues associated with such modes, different partially coherent sources are obtained: sources with a flattened Gaussian profile, twisted Gaussian Schell-model sources with a saturated twist, and a new class of sources having an annular profile. Owing to the shape-invariance property of the underlying modes, the fields radiated by these sources do not change their transverse profile through propagation, except for scale and phase factors. We also prove that, if any such source is covered by a circularly symmetric filter, the new modal structure can be found in a straightforward manner.

ISSN:0950-0340    

DOI:10.1080/09500349808231913

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Two different concepts arise in the context of scalar diffraction theory: the critical points of the stationary phase approximation for the calculation of highly oscillatory integrals (such as the diffraction integrals) and the semiperiodic zone construction (due to Fresnel) for the application of the Huygens principle. The present work aims at showing the relationship between both concepts when a diffracting aperture is present. The main result is that the position of the critical points indicates the most relevant semiperiodic zones for the calculation of the diffracted field. Consequently, simple numerical algorithms for the computation of diffraction integrals will be devised.

ISSN:0950-0340    

DOI:10.1080/09500349808231914

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We study the third harmonic generation via laser interaction with a cold homogeneous plasma, in the one-dimensional approximation. We consider moderate values of the electron plasma density such that the pump laser pulse propagates inside the plasma without changing its shape. Our laser model allows for a finite spectral linewidth, which leads to a damping of the oscillatory behaviour of the third-harmonic power conversion rate as a function of the normalized plasma density, even for very low densities.

ISSN:0950-0340    

DOI:10.1080/09500349808231915

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

It is shown that the angular spectrum of the cross-spectral density is a Wigner distribution function, which is equivalent to the marginal cross-spectral density of the field. The value of the Wigner distribution function at each position of the observation plane results from the contributions of aperture radiator pairs, around each position into the aperture, properly projected along the corresponding direction of propagation. The contributions are weighted by the complex degree of spatial coherence of the illuminating optical field, and their relative weights will be estimated by introducing a ‘visibility’ parameter. There are also forbidden directions, along which certain radiator pairs into the coherence patch cannot contribute depending on the phases of both the complex degree of spatial coherence and the aperture transmittance, but all radiator pairs provide their maximal contributions along orthogonal directions to the aperture plane.

ISSN:0950-0340    

DOI:10.1080/09500349808231916

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor