摘要:

A new interpretation of the non-diffracting Bessel beams is given as a superposition of two fields described by Hankel functions. Within our picture, supported by the Sommerfeld radiation condition, we find that Bessel beams must be of finite transverse extension. Our approach also easily explains propagation characteristics of Bessel-Gauss beams and, in general, the propagation of amplitude modulated Bessel beams. Consequences are discussed and contrasted with the classic theory of Bessel beams.

ISSN:0950-0340    

DOI:10.1080/09500349908231313

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The problem of retrieving the expansion coefficients of a wave front from phase difference measurements in a square domain has been studied using the orthogonality properties of the Gram polynomials. An expression for the coefficients to be obtained independently as weighted sums over the experimental data is given and the influence of measurement noise in the estimate will be analysed, obtaining very good agreement with previous results of zonal and modal estimation with phase difference measurements.

ISSN:0950-0340    

DOI:10.1080/09500349908231314

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Interferometry is an essential field of optical metrology and is adapted in many applications in optics, crystal growth and industry. The crystal growth rate is one of the critical parameters for the growth of optical-quality single crystals. A laser interferometry technique has been developed and applied successfully for crystal growth rate measurement from solution. A He-Ne laser at the wavelength of 633 nm with an output power of 1.5 m W was used in this experiment. The beam was incident on the crystal growing from solution. As the crystal is growing, the path length of the front and back surface reflected beam changes and hence the phase factor of the detector output signal changes continuously. This phase change is directly related to the growth of crystal. The growth rate of theL-arginine phosphate crystal was found to be 6.5 nm s−1.The resolution of the laser interferometry was & deg; which corresponds to 5.02 nm.

ISSN:0950-0340    

DOI:10.1080/09500349908231315

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The intensity of the radiation resulting from stimulated rotational Raman scattering of an elliptically polarized pump beam by gaseous H2was measured as a function of the pump ellipticity in an unseeded experiment. The results show excellent agreement with the predictions of a simple two-beam classical model of the process which incorporates only components at the pump and the Stokes frequencies but includes the effects of pump depletion.

ISSN:0950-0340    

DOI:10.1080/09500349908231316

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The relation between modulus and phase errors introduced by the application of the Fourier transform method to fringe pattern analysis has been established. The theoretical results obtained are proposed for the reconstructed phase error correction. Numerical verification for a one-dimensional fringe pattern, comparison of corrected and non-corrected results obtained for different basic spatial frequencies and an example of application of the proposed correction for real data are given.

ISSN:0950-0340    

DOI:10.1080/09500349908231317

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Z-invariant waveguides with optical axes rotated at & Plus mn; 45 & deg; act as a fourth or a half optical wave plate depending upon whether the length of the waveguide is equal to an odd integer of its fourth or half beat-length respectively. The design of an AlGaAs optical wave plate operated at 1.55 μ is proposed. Such an element should be a key component to transform polarization states of light in optical fibre communication systems.

ISSN:0950-0340    

DOI:10.1080/09500349908231318

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A state of light which is a superposition of the vacuum and the one-photon number state is the simplest state containing phase information. Recently we have shown how a field in such a state might be generated and here we explore its usefulness as a probe for measuring unknown states of light. We find that this probe can be used reasonably simply both to determine completely some pure states of light and to measure the diagonal and nearest off-diagonal elements of the density matrix in the number state basis and hence to obtain the mean sine and cosine of the phase of an unknown mixed state. We suggest further how a field in a superposition of the vacuum and the two-photon number state might be generated and how this can be used as a probe, both to measure the off-diagonal matrix elements second nearest to the diagonal of a mixed state density matrix and to measure the variance of the cosine and the sine of the phase. We also examine the experimentally more likely case where the probe fields are in mixed states and show how the same information about the unknown state can still be retrieved.

ISSN:0950-0340    

DOI:10.1080/09500349908231319

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In white-light interferometry, the position of the peak of the fringe contrast function is directly related to the surface height of the object. In this paper, we present a phase-shifting technique to determine the fringe contrast function using a rotating polarizer, which introduces an achromatic phase shift. The effect of introducing the rotating polarizer phase shifter at the output of the white-light interferometer has been studied. It is shown that the peak of the fringe contrast function does not occur for zero path difference between the arms of the interferometer; it is rather shifted by a constant amount. This shift, however, does not introduce any error in relative height measurements. The experimental results are presented.

ISSN:0950-0340    

DOI:10.1080/09500349908231320

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We report observations of the photorefractive effect in a low glass transition temperature composite based on a bi-functional side chain copolymer of N-methacryloxypropy1-3-(p-nitrophenyl)azo carbazole with N-methacryl-oxypropyl carbazole. A two-beam coupling gain coefficient of 9.4cm−1and an electro-optic coefficient of 9.3pmV−1were measured at the applied electric field of 92.4Vμ−1by the typical two-beam coupling experiment and the compensation electro-optic measurement technique.

ISSN:0950-0340    

DOI:10.1080/09500349908231321

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We present a proposal for quantum key distribution, which is based on improving a long-distance frequency-division interferometer. In contrast to the model of Marrand and Townsend (1995,Opt. Lett,20, (1062)), only one acousto-optical modulator and one unbalanced Mach-Zehnder interferometer are used in this system. We also show how this system is extended to give one-to-any key distribution, in which, only one unbalanced Mach-Zehnder interferometer is used.

ISSN:0950-0340    

DOI:10.1080/09500349908231322

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor