摘要:

Stimulated Raman scattering processes are shown to be of two different types with regard to time symmetry: conventional and with peculiar character of the energy conversion. The peculiar type causes intermixing of waves of degenerate spectrum from different wave quartets and is due to vortical combination forces. It tends to create a coordinated multi-wave motion and can considerably enhance the scattering.

ISSN:0950-0340    

DOI:10.1080/09500348914550211

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A biological activity phenomenon, the cyclose that occurs in citrus fruits or in seaweed, is analysed by using the temporal correlation of speckle patterns produced when a specimen is illuminated with a laser beam. The experimental verification of the phenomenon as well as a theoretical model of the distribution of the elementary moving particles are given. Specific statistical processing of the digital speckle is applied to the computation of correlation coefficients. Experimental results are given for three kinds of biological samples.

ISSN:0950-0340    

DOI:10.1080/09500348914550221

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The statistical properties of time-varying laser speckles appearing on an image transmitted through an image fibre-bundle are studied experimentally and theoretically. The effect of defocusing on a stage of observation is investigated in relation to the stationarity of the detected speckle intensity. It is shown that a large amount of defocusing produces a stationary speckle field for which the correlation function of the speckle intensity variation is obtained in a stable form. This allows a system for monitoring the velocity of moving objects using an image fibre-bundle to be developed.

ISSN:0950-0340    

DOI:10.1080/09500348914550231

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A Fourier filtration algorithm has been applied to speckled fringe patterns, as obtained with the electronic speckle pattern interferometer. The Fourier power spectrum components found are then conveniently manipulated to extract noise that is inherent to the speckled fringes, thus rendering holographic-quality displays. The use of this technique facilitates the computer interferometric analysis of such fringe patterns. Some examples of the phase fringes and the corresponding object displacements obtained using this method are shown.

ISSN:0950-0340    

DOI:10.1080/09500348914550241

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The effect of the multimode structure of a laser field on multichannel multiphoton ionization is investigated, taking the hydrogen atom as a study case. It is found that at moderately high laser intensity the ionization rate into a given channel is changed by varying the number of modes in a similar way to the single-channel multiphoton ionization. At higher intensities the ionization rates saturate, reaching a maximum which is almost independent of the number of modes. In the saturation regime a peaking approximation is performed which gives the ionization rate in a given channel as a simple analytical function of the number of modes and the laser intensity, and provides a useful insight into the characteristic features of the process.

ISSN:0950-0340    

DOI:10.1080/09500348914550251

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The dynamic and statistical properties of a system of an effective two-level atom making two-photon transitions in the binomial state of the field in a lossless cavity are discussed. The binomial state enables the study of the development of the phenomenon of collapses and revivals of the Rabi oscillations as the field state is changed from a pure number state to a coherent state. This is because the binomial state, which is a pure number state in one limit, develops into a coherent state as some parameters are changed appropriately. The effect of Stark shifts arising due to the transitions to virtual levels are also investigated.

ISSN:0950-0340    

DOI:10.1080/09500348914550261

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Raman energy-conversion efficiency in lead vapour as high as 52% was obtained with a pumping XeCl excimer laser used in an unstable-resonator configuration. The characteristics of stimulated Raman scattering in lead vapour pumped by the XeCl laser with unstable and stable resonators were compared in detail. Relaxation oscillations of the Raman-shifted pulse were observed, and these are related to the effect of ground-state depletion of atoms in the lead vapour.

ISSN:0950-0340    

DOI:10.1080/09500348914550271

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The aberrations and apodization of microscope objectives have been measured by observation of the defocus signal in a confocal interference microscope system. Phase distortions can be measured to approximately λ/100, and quantitative information is given about the imaging performance of the lensesin situin the optical system.

ISSN:0950-0340    

DOI:10.1080/09500348914550281

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A simple optical system for synthesizing two-dimensional planar sources having a wide variety of one-dimensional spectral degrees of coherence is analysed. A pupil-mask acting on the dispersed image of a polychromatic incoherent slit is used to control the spectral degree of coherence of the source. Examples of sources exhibiting interesting spectral shifts and modulations in the far field are shown.

ISSN:0950-0340    

DOI:10.1080/09500348914550291

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The possibility of a class of optical echo-producing mechanisms is suggested that does not invoke the phase-reversal action of the second pulse. The mechanisms act selectively on the radiating atomic dipole moments, or on their radiation fields, with a periodic dependence on Δτ, where Δ is the angular frequency of the radiator relative to the central angular frequency of the distribution and τ the interpulse time. In the new formulation, the customary expression for the field radiated by an atomic dipole following a two-pulse excitation sequence is multiplied by a factor periodic in Δτ. It is shown that a sequence of echo pulses is predicted when the average over the radiators is calculated. One such mechanism is proposed: the selective absorption or amplification of the dephased free-induction decay field as they propagate through the sample.

ISSN:0950-0340    

DOI:10.1080/09500348914550301

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor