摘要:

We discuss the quantum Zeno paradox in a three-level system. We are interested in its ability to enhance radiation trapping. This system provides an example of the situation when the spontaneous emission process in one transition is essentially determined by the pump and damping parameters of another transition.

ISSN:0950-0340    

DOI:10.1080/09500349414550841

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We develop a travelling-wave formulation of the theory of quantum optics and apply it to the description of the self-phase modulation of a short coherent pulse of light. The infinite nonlinear phase shift that is produced by the vacuum fluctuations is treated, within our approach, through a renormalization procedure. The renormalized theory successfully describes the nonlinear chirp that the pulse undergoes in the course of its propagation and permits the calculation of the squeezing characteristics of self-phase modulation.

ISSN:0950-0340    

DOI:10.1080/09500349414550851

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Optical patterns, forming in transversely extended nonlinear feedback systems, sometimes consist of ordered or disordered arrangements of many bright circular spots. We derive an approximate analytical description for a localized individual spot for the case of a diffusive Kerr nonlinearity. Each spot represents a Gaussian mode, which induces its own spherical subresonator by supporting a nonlinear lens in the Kerr medium. The properties of these self-induced modes are related to system parameters and their multistable behaviour is investigated. Interaction between two or more spots is estimated, leading to an easy explanation of hexagonal pattern formation.

ISSN:0950-0340    

DOI:10.1080/09500349414550861

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The dynamics of a degenerate two-mode electromagnetic field coupled to a single two-level atom is investigated both analytically and numerically. New quantum effects are discussed concerning the time dependence of the photon number and of its fluctuations, assuming that att= 0 one of the modes is coherent and the other is empty. The field dynamics are dominated by oscillatory net exchanges of a large number of photons between the two modes, displaying amplitude decay. Over a longer time scale, revivals and collapses in the field populations take place. The time scales of these phenomena are much larger than those of the atomic Rabi oscillations decay. Moreover, the system attains a highly non-classical regime in which the field intensity in each mode is subjected to strong fluctuations even for a large initial number of photons in the coherent mode. Various correlations between atomic and field dynamics are pointed out, and the physical origin of the new quantum effects is briefly discussed. Finally, using our fully quantized calculations, we comment on the validity of the atomic homodyne detection proposed by Wilkens and Meystre.

ISSN:0950-0340    

DOI:10.1080/09500349414550871

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A simple model is used to study a tunable amplitude-modulated mode-locked Co:MgF2laser. The dynamics in the case of detuning of the round-trip frequency from resonance with the frequency of modulation is investigated and a rich family of behaviours is found. The dependences of the solutions on the pump rate, the modulation depth and the presence of a filtering element are explored. Observed phenomena are clarified in terms of the pulse evolution inside the cavity which appears to play a considerable role in the dynamics.

ISSN:0950-0340    

DOI:10.1080/09500349414550881

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The nucleation of a pair of vortices in the field of a boundary dominated confocal photorefractive phase-conjugate resonator is studied in detail. A phase instability is seen to precede the nucleation which occurs when the phase step reaches a threshold of π. The validity of a scenario based on the competition of a few modes is verified experimentally using a multichannel optical correlator equipped with matched filters designed to identify the modes presumed by the model.

ISSN:0950-0340    

DOI:10.1080/09500349414550891

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An optical fibre device using a single gradient-index (GRIN)-rod lens and a rotatable blazed reflection grating is proposed for simultaneously realizing the functions of both demultiplexing and multiposition switching. An example of design using the commercially available GRIN-rod lens is shown for the 0·8 μm band multimode fibre use. An extensive tolerance analysis is also done as a basis for fabricating this device. In addition, the potential of a GRIN-rod lens is clarified in terms of the channel separation and the transmission loss.

ISSN:0950-0340    

DOI:10.1080/09500349414550901

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We investigate the separation of the total angular momentumJof the electromagnetic field into a ‘spin’ partSand an ‘orbital’ partL. We show that both ‘spin’ and ‘orbital’ angular momentum are observables. However, the transversality of the radiation field affects the commutation relations for the associated quantum operators. This implies that neitherSnorLare angular momentum operators. Moreover their eigenvalues are not discrete. We construct field modes such that each mode excitation (photon) is in a simultaneous eigenstate ofSzandLz. We consider the interaction of such a photon with an atom and the resulting effect on the internal and external part of the atomic angular momentum.

ISSN:0950-0340    

DOI:10.1080/09500349414550911

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

It is well known that a suitably shaped birefringent material, placed between two polarizers, exhibits a spatial variation in amplitude transmittance. The present article explores the possibility of using such an arrangement as a spatial frequency filter. The advantage of such filters is that the nature of filtering achievable can be changed by rotating any of the two polarizers. The specific case of a biconvex quartz lens as a spatial frequency filter is considered and techniques for real-time edge enhancement and periodic noise removal are discussed. Experimental results are also presented.

ISSN:0950-0340    

DOI:10.1080/09500349414550921

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Effects of crystal orientation which gives rise to parallel and cross polarization coupling have been investigated in degenerate four-wave mixing in absorbing semi-insulating compound semiconductor photorefractive crystals in transmission geometry. The dependence of cross and parallel polarization coupling, and phase conjugate beam of particular polarization, on crystal rotation has been investigated. Considering the pump beam depletion, nonlinear coupled wave equations are obtained and have been solved numerically by a shooting method. The presence of parallel coupling suppresses the cross coupling effect to a large extent and vice versa. Numerical results obtained from computer calculations are presented in graphical form.

ISSN:0950-0340    

DOI:10.1080/09500349414550931

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor