摘要:

An impedance model is used to solve the reflection problem from a multilayer with periodic and Cantor bar fractal distributions. It is based on the calculation of the input surface impedance of such a structure. The method consists of replacing the multilayer reflection problem by a simple reflection problem on a single surface. This approach has the additional advantage that only the fields above the surface should be taken into account. Numerical calculation leads to an iterative method which can be implemented for each polarization mode. The results for the input impedance function of the system and for the reflectance are presented for different iteration states. Also to quantify the comparison between both types of structures we introduce a self-similarity function which correlates orders or states of the same type.

ISSN:0950-0340    

DOI:10.1080/09500349908231357

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

It is demonstrated experimentally that even if the spectral interference between two modes of an optical fibre excited by a low-coherence source is not resolved at its output by a spectrometer of a given resolving power, it is resolved in the Michelson interferometer configuration. In a tandem configuration of a dispersive Michelson interferometer and a two-mode optical fibre, the optical path difference (OPD) in the interferometer is adjusted close to the group OPD between modes to produce a low-frequency spectral modulation that can be processed. Thus, using the Fourier-transform method in processing the measured spectral modulations and subtracting the effect of the dispersive Michelson interferometer, the wavelength dependence of the group OPD between two modes of the optical fibre over a limited spectral region is obtained.

ISSN:0950-0340    

DOI:10.1080/09500349908231358

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this paper the partial coherence transfer function is introduced and its relationship with the Wigner distribution function is established. It depends on the spatial coherence properties and intensity distribution of the illuminating optical field, the imaging properties of the system and the geometry of the imaging.

ISSN:0950-0340    

DOI:10.1080/09500349908231359

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In this paper, we theoretically demonstrate that lenses with negative spherical aberration can be used to reshape a Gaussian Schell-model (GSM) beam to uniform profiles. The numerical calculation results show that, when the coherence of the GSM beam is low, we can achieve uniform GSM beams with smooth top. As the coherence increases, some intensity modulation occurs at the top of the uniform GSM beam. This intensity modulation is caused by the interference of highly coherent light.

ISSN:0950-0340    

DOI:10.1080/09500349908231360

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The effect of thermal noise is studied on the statistical behaviour of the superposition of squeezed and displaced number states. In our analysis we have employed thes-parametrized characteristic function. For such superposition states exact expressions for quasiprobability distribution functions, normalized second-order correlation function, photon-number distribution and phase space distribution are obtained and discussed in detail.

ISSN:0950-0340    

DOI:10.1080/09500349908231361

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We propose a scheme to add/subtract excitations to/from an arbitrary quantum state or the harmonic oscillator. The method displaces the photon-number distribution and leaves its shape unchanged for a wide range of displacements. Mathematically this is realized by the action of phase operators of the Susskind-Glogower type onto the initial quantum state. Consequently, the shape of the phase distribution is preserved unless the number statistics are modified due to displacing it by subtraction onto the vacuum state. Starting with an initially coherent state one may realize pure quantum states displaying either amplitude or phase squeezing. The implementation of the method is based on interactions of the Jaynes-Cummings type, in the case of subtracting quanta one additionally needs to perform measurements on the electronic quantum state of the atoms. Our approach could be used for adding and subtracting both photons on a cavity field and motional quanta of a trapped ion.

ISSN:0950-0340    

DOI:10.1080/09500349908231362

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Mathematically, the simplest state of light containing phase information is a superposition of the vacuum and the one-photon state and, as we show in this paper, such a state is reasonably simple to measure. We investigate how the information contained in a more complicated pure state of light, in particular the ratio of successive number-state coefficients, can be transferred selectively to fields in this two-state superposition for subsequent measurement. By this means the number-state representation of the more complicated state can be ascertained, provided there are no gaps in the number state distribution. We also discuss how to correct for the effect of non-unit efficiencies of the photodetectors involved in the transferral process.

ISSN:0950-0340    

DOI:10.1080/09500349908231363

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We present the most prominent features in two-colour coherent control of high-order harmonic generation using a strongly driven two-level atom model, which are known to generate high harmonics as well as hyper-Raman lines with a plateau and a cut-off. Furthermore, for one laser field case, we find, when the hyper-Raman lines are located at the position of the high harmonics, that the high harmonics are strongly enhanced due to the interference effect between the high harmonics and the hyper-Raman lines. Within these conditions, by combining the laser field with another much weaker laser field, we show plentiful and strong high harmonics in the light spectrum of the driven atomic system.

ISSN:0950-0340    

DOI:10.1080/09500349908231364

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

InSb optical cone concentrators are modelled to assess their optical performance in positive and negative emission modes. The output distribution from the active layer is shown to be isotropic for thin active regions, tending towards Lambertian distribution as the layer thickness increases. Refraction from the emitting surface is shown to make the distribution more Lambertian. Optical efficiencies of straight-sided and Winston cone concentrators are modelled using a ray-tracing program, and those of straight-sided cones also determined using an analytical approximation, which allows use of the distribution derived earlier. The effect on the active layer thickness on the positive and negative emission is also determined. Normal light emitting diode structures are found to be poor positive emitters and to draw large currents when used as negative emitters. A Winston cone of area gain equal ton2is found to be the best option for devices required to work in both positive and negative modes. Intermediate structures are also considered. The optimum active layer thickness is derived for three emitter configurations.

ISSN:0950-0340    

DOI:10.1080/09500349908231365

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor