Showing papers in "Journal of Modern Optics in 1983"
TL;DR: In this article, the authors examined the relationship between the measured decrease in diffuse reflectance observed in the flash photolysis of powdered samples and the concentration of a transient absorbing species and showed that when the transient reflectance changes by less than 10 percent, the change in reflectance is a linear function of transient concentration.
Abstract: Analytical solutions are examined in order to predict how the measured decrease in diffuse reflectance observed in the flash photolysis of powdered samples is related to the concentration of a transient absorbing species. It is shown on the basis of these calculations that when the transient reflectance changes by less than 10 per cent, the change in reflectance is a linear function of transient concentration. Experimental evidence supporting this conclusion is presented from studies of the triplet state of coronene chemisorbed on γ alumina where the concentration of the excited state can also be monitored by measuring luminescence intensity, which is shown to have a virtually identical dependence on the excited state concentration as the transient change in reflectance due to triplet-triplet absorption. Since the luminescence intensity is a linear function of the transient concentration, it follows that this is also true for the transient reduction in diffuse reflectance. Non-exponential decay of the tra...
96 citations
TL;DR: In this article, an efficient method for computing diffraction integrals is presented based on an idea put forward by Hopkins, where the integration domain is divided into subdomains, in each of which the phase and amplitude are approximated by simple functions which make it possible to evaluate the resulting integral in terms of known functions.
Abstract: An efficient method for computing diffraction integrals is presented. It is based on an idea put forward by Hopkins [1]. The integration domain is divided into subdomains, in each of which the phase and amplitude are approximated by simple functions which make it possible to evaluate the resulting integral in terms of known functions. While Hopkins employed a linear approximation to the phase and a constant approximation to the amplitude, we here approximate both the phase and the amplitude by parabolas. A comparison of the results of our method with those of Hopkins's method shows that our method requires fewer subdomains and less computation time to yield a desired accuracy. Another advantage of our method is that it can be applied to apertures of a general shape without significant loss of accuracy.
76 citations
TL;DR: In this article, the authors studied the diffraction field of two spatially separated linear diffraction gratings under incoherent illumination, based on the spatial superposition of many mutually incoherent Talbot (self-imaging) effects.
Abstract: Characteristics of the diffraction field of two spatially separated linear diffraction gratings under incoherent illumination are studied. The analytical model is based on the spatial superposition of many mutually incoherent Talbot (self-imaging) effects. It permits a simple explanation of the basic parameters of the ‘incoherent’ diffraction images: axial localization, spatial period and lateral displacement. The moire fringe formation in space, the imaging of a grating by a second grating, and the Lau effect are considered; the results are compared with the former studies in the literature.
73 citations
TL;DR: In this article, the authors show that solitons emerge in such a medium under conditions of two-dimensional optical beam scanning along the medium surface, and have non-coinciding propagating directions of the amplitude and phase fronts.
Abstract: Special features of generating a self-induced transparency in a medium with both resonant and non-resonant (Kerr-type) nonlinearities are considered. Soliton solutions of the Maxwell-Bloch equations are found, taking into account the diffraction divergence of the light beam. It is shown that solitons emerge in such a medium under conditions of two-dimensional optical beam scanning along the medium surface, and have non-coinciding propagating directions of the amplitude and phase fronts. As a necessary condition for the existence of solitons, there is a definite relationship between the scanning velocity and the parameters of the medium and radiation.
69 citations
TL;DR: In this article, the transverse and longitudinal spatial coherence properties of the light beams generated by planar gaussian Schell-model sources are discussed and the relation of the present work to the analysis of speckle size is briefly discussed.
Abstract: The transverse and longitudinal spatial coherence properties of the light beams generated by planar gaussian Schell-model sources are discussed. It is found that for all gaussian Schell-model beams the ratio of the transverse coherence length to the beam width remains invariant upon propagation. An examination of the longitudinal coherence for both on-axis and off-axis pairs of points indicates that the longitudinal coherence will not, in general, die out as the separation between the points is increased. Rather, the degree of longitudinal coherence will approach a finite (non-zero) value as long as the source contains a finite coherence area, regardless of how small this area may be. Gaussian quasihomogeneous beams are studied as a limiting case. The relation of the present work to the analysis of speckle size is briefly discussed.
66 citations
TL;DR: In this paper, an n-fold measure of the degree of polarization associated with an N×N coherency matrix characterizing N pencils of radiation is discussed, which is cast in terms of the N possible scalar invariants of the matrix and automatically takes into account possible rank deficiency.
Abstract: An n-fold (n=2,…,N) measure of the degree of polarization associated with an N×N coherency matrix characterizing N pencils of radiation is discussed. The measure is cast in terms of the N possible scalar invariants of the coherency matrix and automatically takes into account possible rank deficiency. When N = 2, the single polarization measure reduces to the usual expression for polarization as the fraction of the intensity contained in the polarized component. The N = 3 case is discussed as an illustrative example, with special reference to the rank deficiency of a plane wave arbitrarily oriented with respect to the given coordinate system. Finally, these results are used to redevelop von Laue's theory of the thermodynamic entropy of partially coherent pencils of radiation.
65 citations
TL;DR: In this paper, the photon correlation and structure functions for Gaussian-lorentzian light were compared for diffusion measurements on highly polydisperse systems and it was shown that at high mean count rates, the structure function gives the faster estimate.
Abstract: Estimator variances of photon correlation and structure functions can be calculated exactly for gaussian-lorentzian light if the total experimental duration is large compared with the coherence time. For low photon count rates, the correlation function consistently shows the better noise performance. At high mean count rates, the structure function gives the faster estimate, particularly for the high-frequency part of the signal. This suggests the usefulness of photon structure functions for diffusion measurements on highly polydisperse systems.
56 citations
TL;DR: In this article, second-harmonic generation inside a coherently driven optical cavity and subharmonic generator internal to the laser cavity are predicted to lead to self-pulsing, period doubling and chaos.
Abstract: Instabilities leading to self-pulsing, period doubling and chaos are predicted to occur in two simple systems in nonlinear optics. Namely, second-harmonic generation, inside a coherently driven optical cavity, and subharmonic generation internal to the laser cavity.
54 citations
TL;DR: In this article, the authors introduce the Wigner distribution function (WDF) as a self-windowed complex spectrogram and suggest some methods for the optical generation of the WDF of two-dimensional signals.
Abstract: We introduce the Wigner distribution function (WDF) as a self-windowed complex spectrogram and suggest some methods for the optical generation of the WDF of two-dimensional signals. The resulting WDFs, since they are four-dimensional functions, are represented as sectional images displayed either in parallel or as temporal sequences. We give some experimental results for real-valued input signals obtained from different coherent-optical WDF processors.
54 citations
TL;DR: In this paper, a new approximate theory for scattering from arbitrary rough surfaces is presented, which gives the exact result, to the first order, when the depth of the asperities tends to zero.
Abstract: A new approximate theory for scattering from arbitrary rough surfaces is presented. It is shown that this theory gives the exact result, to the first order, when the depth of the asperities tends to zero. On the other hand, we prove that this is not the case for formulae relying upon the Kirchhoff approximation, even in cases for which many authors have claimed their validity. Many applications can be envisaged, in particular to direct or inverse scattering from random rough surfaces.
54 citations
TL;DR: In this paper, surface polaritons were used to detect magnetic waves at surfaces and interfaces. But they did not consider the effect of the magnetic field on the surface of the surface.
Abstract: (1983). Surface Polaritons: Electromagnetic Waves at Surfaces and Interfaces. Optica Acta: International Journal of Optics: Vol. 30, No. 11, pp. 1501-1501.
TL;DR: In this paper, the intensity distribution of diffraction patterns has been measured for focusing systems of Fresnel numbers near unity, and the results, presented in intensity charts and in photographs, are compared with theoretical predictions along the axis and in various planes parallel to the geometric focal plane.
Abstract: The intensity distribution of diffraction patterns has been measured for focusing systems of Fresnel numbers near unity. Results, presented in intensity charts and in photographs, are compared with theoretical predictions along the axis and in various planes parallel to the geometric focal plane. Close agreement between them has been obtained.
TL;DR: In this article, the diameters of the fibres/filaments are selected so that the light transmissivity of the composite has reduced sensitivity with respect to mismatch of the refractive indices of the liquid crystal and the filament.
Abstract: A liquid crystal device comprises a layer of fibres or filaments (15) permeated with liquid crystal material, the layer (15) being located between electrodes (13, 14) by means of which an electric field can be applied across the layer to vary the transmissivity of the liquid crystal/fibre composite. The diameters of the fibres/filaments are selected so that the light transmissivity of the composite has reduced sensitivity with respect to mismatch of the refractive indices of the liquid crystal and the fibres/filaments.
TL;DR: In this paper, the imaging properties of Fresnel zone plates are discussed in terms of possible manufacturing inaccuracies such as non-circularity and displacement of zones, and degradation of the on-axis intensity is used to establish manufacturing tolerances.
Abstract: The imaging properties of Fresnel zone plates are discussed in terms of possible manufacturing inaccuracies such as non-circularity and displacement of zones. The degradation of the on-axis intensity is used to establish manufacturing tolerances.
TL;DR: In this article, a regularized algorithm for the recovery of band-limited signals from noisy data is described, which is characterized by a single parameter and is shown to have useful properties, the former offering the advantage of flexibility and the latter a potential for rapid data processing.
Abstract: A regularized algorithm for the recovery of band-limited signals from noisy data is described. The regularization is characterized by a single parameter. Iterative and non-iterative implementations of the algorithm are shown to have useful properties, the former offering the advantage of flexibility and the latter a potential for rapid data processing. Comparative results, using experimental data obtained in laser anemometry studies with a photon correlator, are presented both with and without regularization.
TL;DR: In this article, a model of light scattering by large rough particles is proposed which is based on the high-energy approximation, the laws of geometrical optics and a mathematical description of the properties of the particles roughness.
Abstract: A model of light scattering by large rough particles is proposed which is based on the high-energy approximation, the laws of geometrical optics and a mathematical description of the properties of the particles roughness. The calculated intensities and polarizations as functions of scattering angles agree well with experimental results except in the case of metallic particles.
TL;DR: In this article, the self-imaging phenomenon of coherent and partially coherent fields is described as eigenfunctions of the operator that represents the solution of the Helmholtz equation.
Abstract: The propagation of light in free space yields images of a certain class of objects. This effect, discovered 150 years ago by Talbot, is known as ‘self-imaging’. The self-imaging phenomenon, or the periodic properties of coherent and partially coherent fields, are described in this paper as eigenfunctions of the operator that represents the solution of the Helmholtz equation. Using this simple treatment, we state the necessary and sufficient conditions for self-imaging in coherent and partially coherent fields. We indicate that certain laterally aperiodical, partially coherent fields also exhibit self-imaging properties. Our treatment is exact, but it disregards evanescent waves.
TL;DR: In this paper, the changes in the Fraunhofer diffraction patterns encountered when planar objects become titled with respect to the optical axis are investigated. But the results are limited to the untilted case.
Abstract: Attention is drawn to the changes in the Fraunhofer diffraction patterns encountered when the planar objects become titled with respect to the optical axis. The differences between the far-field images observed in the well-known untilted case and the one investigated are shown and discussed using examples of familiar objects, such as square or rectangular apertures and linear diffraction gratings.
TL;DR: In this paper, the antireflection effect of a moth eye surface was used to produce a broadband waveguide output window for a tunable gyrotron in the millimetre and sub-millimetre wave region.
Abstract: The antireflection effect of a moth eye surface is used to produce a broadband waveguide output window for a tunable gyrotron in the millimetre and sub-millimetre wave region. The transmission of the window has been measured and is found to be in qualitative agreement with theoretical considerations.
TL;DR: In this paper, the conditions for sub-poissonian photon statistics and squeezed states in the field of resonance fluorescence of a two-state atom were studied and the conditions as a function of the detuning from resonance, the linewidth and the Rabi frequency have some overlap.
Abstract: We study the conditions for sub-poissonian photon statistics and squeezed states in the field of resonance fluorescence of a two-state atom. These conditions as a function of the detuning from resonance, the linewidth and the Rabi frequency have some overlap, but they are largely complementary. Super-poissonian statistics arise for small linewidths and large detunings, irrespective of the Rabi frequency. Squeezed states require small linewidths and either low or moderate Rabi frequencies, or large detunings from resonance.
TL;DR: In this paper, the mutual intensity of partially coherent illumination is shown to be periodic in the lateral direction and also in the longitudinal direction for quasi-monochromatic light and cosine periodicity.
Abstract: If the mutual intensity of partially coherent illumination is periodic in the lateral direction then it is also periodic in the longitudinal direction This statement is proved for quasi-monochromatic light and for a cosine periodicity Next an experimental set-up for the production of periodic mutual intensities is proposed Finally, the theoretical result is generalized to other than cosine-shaped periodicities
TL;DR: In this paper, a Taylor series expansion in a region close to the cusp at X = Y = 0, and on asymptotic approximations in regions far from the caustic are presented.
Abstract: The field in the neighbourhood of a cusp of a caustic can be expressed in terms of a function of two variables, P(X,Y), known as Pearcey's integral or the Pearcey function. In this paper we develop efficient algorithms for computing this function and its derivatives P/ X and P/ Y. They are based on a Taylor series expansion in a region close to the cusp at X = Y = 0, and on asymptotic approximations in regions far from the cusp. The asymptotic results are given in terms of contributions of isolated stationary points in regions far from the caustic, and in terms of the Airy integral function and its derivative in a region close to the caustic. Three terms in the asymptotic expansions are used, and they give an accuracy for P(X,Y) better than 0·006 in amplitude and 0·6° in phase at distances from the cusp greater than (X2 +Y2 )1/2 = 4.
TL;DR: In this paper, a regularized algorithm is proposed, which converges to stable solutions, and the efficiency of both algorithms is tested by means of numerical simulations, and it is shown that a previous algorithm proposed for extrapolating the data to the missing cone in Fourier space is unstable in the presence of noise because of the ill-posedness of the problem.
Abstract: The tomography problem is investigated when the available projections are restricted to a limited angular domain. It is shown that a previous algorithm proposed for extrapolating the data to the missing cone in Fourier space is unstable in the presence of noise because of the ill-posedness of the problem. A regularized algorithm is proposed, which converges to stable solutions. The efficiency of both algorithms is tested by means of numerical simulations.
TL;DR: The dark field, empty field and instrument accommodations were measured for a number of emmetropic and ametropic subjects to investigate the natural individual variation in these accommodation as mentioned in this paper.
Abstract: The dark-field, empty-field and instrument accommodations were measured for a number of emmetropic and ametropic subjects to investigate (1) the natural individual variation in these accommodation ...
TL;DR: In this article, the contrast of the far-field intensity pattern, generated by illuminating a small area of a gaussian random diffuser with fractal slope, exhibits a characteristic power-law dependence on illuminated area.
Abstract: It is shown that the contrast of the far-field intensity pattern, generated by illuminating a small area of a gaussian random diffuser with fractal slope, exhibits a characteristic power-law dependence on illuminated area.
TL;DR: In this paper, light scattering in solids is studied in the context of light-scattering in Solids, and the authors propose a light scattering algorithm for solids with light scattering.
Abstract: (1983). Light Scattering in Solids III. Optica Acta: International Journal of Optics: Vol. 30, No. 4, pp. 411-411.