摘要:

Two photon absorption is considered in the context of second order coherence measurements. We examine second order interference fringes for the typical Doppler free spectroscopic layout which involves a retro-reflecting mirror. The fringes are manifested in the wings of the absorption spectrum and their observability requires partial decoherence of the exciting laser light.

ISSN:0950-0340    

DOI:10.1080/09500349608232847

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A Ti target was submitted to laser ablation in low ambient pressure N2. Electron microscopy examination of the cross-section of the crater zone forming on the Ti target, and XPS analyses, indicate that there is a small effect on the nitridation processes taking place on and in the vicinity of the target. The studies show a zone influenced by the multipulse laser treatment extending beneath the crater down to a depth of the same order of magnitude as the crater depth (i.e. ∼ 10 μm). In this zone, TiN could be identified as being present only in traces, while the whole zone exhibited a layer structure with differences in morphology and mechanical wear.

ISSN:0950-0340    

DOI:10.1080/09500349608232848

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A parametric characterization of general light pulses propagating through single-mode fibres is proposed. The theory is applicable to arbitrary partially coherent sources. Two new parameters are defined that encompass the properties of both the light source and the modulating signal: one of them is shown to represent the capability of a pulse of having narrow temporal and spectral widths simultaneously; the other can be used to determine the Plane of the fibre where the pulse width is minimum. The relationship between both parameters and the transmission capacity of the fibre is considered. Propagation of the above parameters through single-mode fibres (including the vicinity of the zero second-order dispersion point) is analysed. As an illustrative example, the special case of a partially coherent source with a Gaussian-profile coherence function, modulated (chirping included) by a Gaussian-amplitude signal, is also studied.

ISSN:0950-0340    

DOI:10.1080/09500349608232849

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A thin transparent film on a reflecting surface produces significant changes in the spectral reflectance of the surface. We show that these changes can result in errors and ambiguities with white-light interferometric surface profilers.

ISSN:0950-0340    

DOI:10.1080/09500349608232850

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Depending on the input polarization of the laser beam propagating through BTO:Cd and BSO:Mn crystals, changes in the optical rotation and optical transmittance are self-induced in the crystal. A model for explaining the phenomenon is proposed. This is based on the anisotropic energy exhange due to the reflection holographic grating produced in the crystals' volume by the interference of the forward propagating beam and the beam reflected by the rear surface of the crystals.

ISSN:0950-0340    

DOI:10.1080/09500349608232851

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A photorefractive optical processor for accurate holographic associative memory that uses a spatial-encoding method is presented. The associative memory of both binary images and gray-scale images can be performed with this processor. The experimental results have proved that spatial-encoding can efficiently increase the addressing accuracy of real-time holographic associative memory in a simple way.

ISSN:0950-0340    

DOI:10.1080/09500349608232852

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We have investigated the ability of Rh:BaTiO3to couple and diffract light via electro-optic and absorption gratings. The photorefractive two-beam coupling gain we observed was very high, showing the potential of this crystal to efficiently amplify weak signals. Also, to estimate the strength of the gratings formed during beam coupling, we have measured diffraction efficiency, which was as high as 80%. Additionally an improvement in the response time, as compared to an undoped BaTiO3crystal was observed.

ISSN:0950-0340    

DOI:10.1080/09500349608232853

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We report the calculation of the optical interference phase directly from double-pulsed electronic speckle pattern interferometry (ESPI) addition fringes using phase-stepping techniques, for an object undergoing harmonic vibration. The optical phase is used to calculate the harmonic-vibration amplitude and phase. This involves shifting the laser double pulses with respect to the object-vibration phase. Two techniques to improve the addition fringe visibility have been proposed in the literature: subtraction of a reference interferogram recorded when the object is stationary from an addition fringe pattern, and subtraction of addition patterns. We present a mathematical analysis of these two techniques and comment on some misconceptions that have arisen in the literature. These two techniques offer less immunity to environmental disturbances than addition ESPI, but improve fringe visibility. Phase calculation for the latter case (subtraction of addition fringes) is presented.

ISSN:0950-0340    

DOI:10.1080/09500349608232854

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Pseudocolour encoding of holographic images by lensless one-step rainbow holography with a synthesized slit is proposed. When a different portion of the object is recorded the reference wave is incident at a different angle θ and during each exposure the incident angle changes continuously around this angle θ. The pseudocolour holographic image is obtained by white-light reconstruction of the lensless one-step rainbow hologram with synthesized slit. The basic advantage of this technique is the elimination of a narrow slit and a lens in the encoding process. The theoretical analysis and experimental result are presented.

ISSN:0950-0340    

DOI:10.1080/09500349608232855

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Coherent propagation of an optical pulse in a medium with a second-order resonance is investigated when we include both the dynamical Stark effect and a population-dependent refraction index. We show how to obtain the general solution when the incident pulse has no phase-modulation. The amplitude-modulation of the incident pulse can be arbitrary as can be the initial state of the medium. This general solution is reduced to obtaining the solution of an ordinary differential equation and quadratures. For an initially de-excited medium, the solution reduces to that given by Poluektovet al. {I. A. Poluektov, Yu. M. Popov and V. S. Roitberg, 1975,Kvant. Elektron. (Moscow), 2, 1147 [1975,Sov. J. Quant. Electron.,5, 620]}. We give some illustrative examples of solutions for various initial profiles. It is also shown that the oscillating two-stream instability (OTSI) from plasma physics is equivalent to the Maxwell-Bloch equations for degenerate two-photon propagation. We give a solution for the OTSI which contains five arbitrary real functions.

ISSN:0950-0340    

DOI:10.1080/09500349608232856

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor