摘要:

We present a rigorous formalism to solve the problem of diffraction of light at a periodically corrugated boundary between an isotropic medium (dielectric or metal with losses) and a biaxial crystal. The method applies to gratings illuminated either from the isotropic or from the biaxial side by waves with wave vectors inclined at an arbitrary angle with respect to the grooves and for arbitrary orientations of the crystal optic axes. Using a nonorthogonal curvilinear coordinate transformation that simplifies the boundary conditions at the grating interface and writing Maxwell's equations for the covariant components of the fields in the transformed frame, the problem can be reduced to the numerical solution of a system of first order differential equations with constant coefficients. The application of the method is illustrated in two cases: (i) diffraction of s- and p-polarized waves at a sinusoidal boundary between a transparent dielectric and a biaxial crystal and (ii) excitation of surface plasmons along the corrugated interface between a metal and a biaxial crystal.

ISSN:0950-0340    

DOI:10.1080/09500349708232896

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This study deals with the topic of reflection and refraction of light from the boundary of a high-gain saturating laser amplifier. Expressions for the electric field and intensity reflection and transmission coefficients are obtained for the case of a wave in a uniform dielectric that is incident normally on a nonlinear saturating active medium. Bistability effects are predicted even for the simplest case of zero frequency detuning from the line centre of the saturating transition.

ISSN:0950-0340    

DOI:10.1080/09500349708232897

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We study the non-classical properties of Schrödinger cat states given as superpositions of two-modeSU(1, 1) andSU(2) coherent states. TheSU(1, 1) andSU(2) coherent states themselves have strong non-classical properties and we find that these properties are enhanced at least for some superpositions. We propose a method of generating such states in the context of cavity quantum electrodynamics.

ISSN:0950-0340    

DOI:10.1080/09500349708232898

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The optical properties of amorphous Ga20Se80−xBix(a-Ga20Se80−xBix) thin films (where x = 0, 5, 10, 15 and 20) have been studied in the wavelength range (450-1400 nm). It is found that the optical bandgap decreases with increasing bismuth content in the a-Ga20Se80−xBixsystem. The value of the refractive indexndecreases, while the value of the extinction coefficientkincreases with increasing photon energy. The dc conductivity measurements of a-Ga20Se80−xBixthin films have also been reported in the temperature range 287-318 K. It is observed that the activation energy decreases with increase in the metallic impurity in a-(Se-Ga) binary alloys.

ISSN:0950-0340    

DOI:10.1080/09500349708232899

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We discuss, with illustrations drawn from the simple example of a dielectric grating under total internal reflection illumination, the use of electric field, energy density and Poynting vector as tools for understanding phenomena associated with dielectric gratings. The electric field has greatest direct observational interest and exhibits patterns of nodes and antinodes that are both expected and intuitive. The energy density, although not directly linked with photoelectric response, has readily understood global patterns. The Poynting vector has more elaborate structure, involving patterns of curls, but the patterns are sensitive to small changes in illumination angle or groove depth. Plots of Poynting vectors may not be as useful for dielectric structures as they are for metals.

ISSN:0950-0340    

DOI:10.1080/09500349708232900

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The stationary emission and stability of a three-level cascade laser in which two fields of different frequencies can be simultaneously amplified is investigated under conditions of cavity detuning. Different monomode and bimode solutions are found and analysed for the effects of different pitchfork and Hopf bifurcations. At moderate cavity detunings, features different from those observed in other classes of lasers are found, such as for instance a decrease in the instability threshold when detuning is introduced. Particular attention is paid to the case of resonance of the two-photon transition, which allows us to study the continuous evolution, when detuning is increased, of a resonant cascade laser towards a pure two-photon laser. In particular, this establishes the origin of some features which are characteristic of two-photon lasers.

ISSN:0950-0340    

DOI:10.1080/09500349708232901

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A novel kind of optical fibre ring cavity, which acts as ‘optical capacitor’, is presented. As incident light energy can be stored in this kind of cavity, the beam intensity in it may be increased to a value which is much higher than the input intensity. Some applications are also proposed, such as enhancing the efficiency of nonlinear optical conversions, reducing the drive voltage for electro-optic switches or modulators, increasing the energy utilization ratio for optical switches or modulators and so on.

ISSN:0950-0340    

DOI:10.1080/09500349708232902

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The propagation lengthLof long-range surface optic waves in islandized Ag films sandwiched by identical dielectrics at a wavelength of 632·8 nm has been measured. Two measurement methods were adopted: (i) an attenuated total reflection (ATR) method, and (ii) a method involving measuring the spatial distribution of the reflected intensity in an ATR geometry. By using both methods, a value forLof ∼480 μm was obtained for a mass thickness of 2·7 nm.

ISSN:0950-0340    

DOI:10.1080/09500349708232903

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

As evidenced by many physiological and psychophysical reports, the receptive fields of the first-stage set of mechanisms of the visual process fit to two-dimensional (2D) compactly supported harmonic functions. The application of this set of band-pass filter functions to the input signal implies that the visual system carries out some kind of conjoint space/spatial frequency transform. Assuming that a conjoint transform is carried out, we present in this paper a new characterization of the visual system performance by means of a weighting function in the conjoint domain. We have called this weighting function (in the particular case of the Gabor transform) the Gabor stimuli Sensitivity Function (GSF) by analogy with the usually employed weighting function in the Fourier domain: the Contrast Sensitivity Function (CSF). An analytic procedure to obtain this conjoint weighting function from the psychophysical measurements of the CSF is derived. The accuracy of the procedure is proved showing the equivalence between some experimental Fourier weighting functions (2D CSFs), and the corresponding GSFs. The main advantage of this new characterization is that a weighting function in a space/spatial frequency domain can account for spatially variant behaviour, which cannot be included in a unique CSF, so a single GSF would be needed to include extra-foveal and large eccentricity behaviour. One example is given of how non-homogeneous systems can be easily characterized in this way.

ISSN:0950-0340    

DOI:10.1080/09500349708232904

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We examine some properties of a class of partial phase states of a single field mode. The quasiprobability distribution function and the phase properties of both the generalized geometric and even geometric states are investigated. The relation between the coherent phase states and theSU(1, 1) coherent states is sought.

ISSN:0950-0340    

DOI:10.1080/09500349708232905

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor