摘要:

The dynamic processes of the mode-locked laser based on a nonlinear auxiliary cavity containing a nonlinear frequency-doubling crystal have been studied systematically in this paper. The formulae for the output pulse width of this mode-locked laser in a dynamic equilibrium state are given, and our experimental results are shown to be in agreement with the theoretical calculations. Finally, we have also reported the dependence of laser output characteristics on some parameters.

ISSN:0950-0340    

DOI:10.1080/09500349414551241

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The line spread function is a classical figure of merit for the modulation transfer function assessment of an optical system. However, this test cannot be directly applied to sampled imaging systems as they often exhibit aliasing effects. The purpose of this paper is to define a new figure of merit which allows the characterization of the transfer of all spatial frequencies even those which are placed after the Nyquist frequency. An experiment has been carried out to demonstrate the effectiveness of this new test.

ISSN:0950-0340    

DOI:10.1080/09500349414551251

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

New coherent states of a harmonic oscillator in a finite-dimensional Fock space are introduced. Some properties of these coherent states are discussed. The second-order squeezing of these coherent states with respect to the quadrature operators is studied in detail. In particular, for a two-state system the arbitrary higher-order squeezing of these states is investigated. It is shown that these coherent states exhibit much richer squeezing properties than the coherent states of a usual harmonic oscillator in an infinite-dimensional Fock space. It is found that these coherent states have not only second-order squeezing but also higher-order squeezing with respect to the quadrature operators of the field under consideration.

ISSN:0950-0340    

DOI:10.1080/09500349414551261

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The properties of entropy evolution of the bimodal field interacting with an effective two-level atom via the Raman transition are studied. The influences of the initial average photon number and of the atomic coherence on the evolution of the bimodal field entropy are examined. It is shown that the bimodal field is in a pure state only under certain conditions in the early stages of time evolution and later tends to a statistical mixture state with maximum entropy values; the bimodal field remains strongly entangled with the atom.

ISSN:0950-0340    

DOI:10.1080/09500349414551271

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A spatial dependence of the demodulated signal over the cross-section of a laser beam used for saturation spectroscopy has been observed. If the detector is not exposed to the full beam this spatial dependence causes a distortion of the line-shape. In extreme cases this distortion can lead to frequency shifts as large as 15% of the full width of the resonance. A model is presented in which the self-focusing effect acts to separate spatially the different frequency components of the modulated laser beam and thus allows for a spatial inhomogeneity of the demodulated signal. Numerical evaluation of the model agrees well with the experimental data provided a strong enhancement of the beam convergence in the absorption medium is applied.

ISSN:0950-0340    

DOI:10.1080/09500349414551281

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We report the first demonstration of second harmonic generation (SHG) in ion implanted lithium niobate optical waveguides. For both ordinary and extraordinary index profiles a computer program was developed to simulate the positions of the modes within the optical well. With the help of this program the theoretical possibility of SHG using mode matching conditions within the guide was then studied as a function of the guide depth and temperature, and from these predictions, practical guides were constructed. Initially, SHG Cerenkov radiation was observed with leaky single implanted guides. Mode matched SHG from m = 0 to m = 2 was subsequently achieved by means of a multiple energy implant which was able to confine both fundamental and harmonic waves. Allowing for coupling and transmission losses, the corrected conversion efficiency is 0–018% W−1which compares favourably to a theoretical prediction for this guide of 0–020% W−1. In this case a wide temperature tuning range was obtained.

ISSN:0950-0340    

DOI:10.1080/09500349414551291

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A composite optical waveguide structure is proposed which is calculated firstly to extend the operating range of second-harmonic generation to shorter wavelengths, and secondly to improve its conversion efficiency. In an example using LiNbO3it is shown that second-harmonic output is feasible down to 435 nm and the overall efficiency is doubled relative to mode matching in a simple waveguide structure.

ISSN:0950-0340    

DOI:10.1080/09500349414551301

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We study the evolution of a initially coherent state of an electromagnetic field propagating in a Kerr medium with saturable nonlinearity. By using the quantum phase distribution formalism, we analyse the dependence of the output signal phase configuration upon input field amplitude. We observe that the saturation of the nonlinear contribution of the refractive index of the propagation medium introduces interference effects that compromise the observation of macroscopically well distinguishable components of the output state. For input amplitudes much larger than a characteristic saturation amplitude the final state differs from the input state only by an overall phase shift. Possible relevance of the present results in the experimental search of Schrödinger cat-like states using semiconductor-doped glass optical fibres is discussed.

ISSN:0950-0340    

DOI:10.1080/09500349414551311

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In the design of a diode-pumped slab solid-state laser, the knowledge of the temperature distribution and the thermal lensing in the medium is very important when attempting to achieve high output power in the TEM00mode. A general 3D analytical calculation is given of the temperature distribution in a slab of finite size, side-pumped by many laser diodes; the spatial distribution of the pump power is taken into account. An approximate thermal focal length is calculated from the temperature distribution. Three different ways of cooling the slab are treated and included in the model as boundary conditions. We derive general solutions of the heat distribution for each case of cooling. The test of the model includes numerical calculations applied to the case of our slab prototype and a comparison with experimental measurements is made.

ISSN:0950-0340    

DOI:10.1080/09500349414551321

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We present a simple model in which a twisted Gaussian Schell-model beam is produced by an incoherent superposition of ordinary Gaussian beams. The meaning and some direct consequences of the model are given.

ISSN:0950-0340    

DOI:10.1080/09500349414551331

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor