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Showing papers in "Pure and Applied Optics: Journal of The European Optical Society Part A in 1998"


Journal ArticleDOI
TL;DR: In this article, a simple diffusion model was proposed to account for the essential dynamic features of surface-relief grating formation, accounting for intensity and polarization dependences, and it opened new perspectives associated with optically controlled anisotropic diffusion.
Abstract: Large-amplitude negative holographic surface-relief gratings are optically induced by resonant visible exposure in azobenzene dye-containing polymers. We propose a simple diffusion model accounting for the essential dynamic features of surface-relief grating formation. It accounts for intensity and polarization dependences. Understanding of the process appears to be essential for holographic grating applications. It opens new perspectives associated with optically controlled anisotropic diffusion.

280 citations


Journal ArticleDOI
TL;DR: In this article, a beam coherence-polarization matrix is proposed for describing the properties of a quasi-monochromatic, beam-like field that is both partially polarized and partially coherent from the spatial viewpoint.
Abstract: We present an approach for describing the properties of a quasi-monochromatic, beam-like field that is both partially polarized and partially coherent from the spatial standpoint It is based on the use of a single matrix, called the beam coherence-polarization matrix, whose elements have the form of mutual intensities This approach, which can be viewed as an approximate form of Wolf's general tensorial theory of coherence, appears to be very simple, yet it is able to cover significant aspects of the beam behaviour that would not be accounted for by a scalar theory or by a local polarization matrix approach A peculiar interference law applying to mutual intensities is derived We show through simple examples how this approach leads to distinguish fields that would appear identical in a scalar treatment or in a local polarization matrix description Hints for extensions are given

152 citations


Journal ArticleDOI
TL;DR: In this article, the laser-induced chlorophyll (Chl) fluorescence spectrum in vivo at the steady state was investigated as a function of the leaf temperature between 25 and at low light intensity.
Abstract: The laser-induced chlorophyll (Chl) fluorescence spectrum in vivo at the steady state was investigated as a function of the leaf temperature between 25 and at low light intensity . The ratio between the red and far-red fluorescence bands, F685/F730, was seen to decrease with decreasing leaf temperature, while the fluorescence intensity at both the 685 and 730 nm peaks increased going from 25 to . This behaviour appears to be the same in chilling-sensitive plants ( Lycopersicon esculentum and Phaseolus vulgaris) as well as in chilling-tolerant species ( Pisum sativum and Vicia faba). Under high light intensity , at controlled temperature, F685/F730 as well as the total fluorescence intensity was seen to decrease with irradiation time. Since photosystem I (PSI) contributes to the F730 emission band only, while photosystem II (PSII) contributes to both F685 and F730, the above results can be explained as being due to the change with light intensity and temperature of quenching processes that affect PSII more than PSI. Changing the light intensity impinging on the leaf, the total Chl fluorescence increases with increasing light intensity to a maximum reached at about , then it decreases to values close to the dark level of fluorescence . The Chl fluorescence spectrum was seen to vary in shape by changing the excitation wavelength. The well known process of Chl fluorescence reabsorption is responsible for the decrease in the F685/F730 going from less (440 nm) to more (635 nm) penetrating excitation light. With UV excitation at 337 nm, an unexpected lower value for F685/F730 with respect to blue excitation was found.

95 citations


Journal ArticleDOI
TL;DR: The physical background of singular optics dealing with phase singularities in light waves is reported as a new chapter in modern optics in this paper, and a review of the current status of nonlinear singular optics is presented.
Abstract: The physical background of singular optics dealing with phase singularities in light waves is reported as a new chapter in modern optics. A review of the current status of nonlinear singular optics is presented.

51 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present results of theoretical and experimental investigations into spontaneous emission alteration and nonlinear optical effects in thin-film multilayer devices, and show enhancement of the spontaneous emission power spectrum of an emitter localized within a photonic band gap structure.
Abstract: We present results of theoretical and experimental investigations into spontaneous emission alteration and nonlinear optical effects in thin-film multilayer devices. We begin with a brief section on one-dimensional photonic band gaps (PBGs) and photonic band edges. We then introduce the concept of nonlinear optical effects in PBG structures with the outline of the method of operation of an all-optical PBG switch. Next, we model a device that exhibits passive anisotropic optical transmission—the analogue of the electronic diode. This structure is designed to exhibit a greater shift in the location of the photonic band edge for light incident from one direction than from the opposite direction. Finally, we show enhancement of the spontaneous emission power spectrum of an emitter that is localized within a PBG structure—without the use of a typical microcavity—for frequencies near the photonic band edge. Two slightly different AlAs/AlGaAs/GaAs semiconductor PBG light emitting diodes (LEDs) were designed and fabricated. The emission spectra of these structures were measured and compared with that of a reference GaAs LED. We use a novel method for modeling the emission rate from within the structures.

45 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of lattice imperfections on the evaluation of fundamental physical parameters related to electro-optic device behaviour is discussed, and the materials produced by these methods are of a quality and performance suited to their use as commercial electrooptic devices.
Abstract: Studies are outlined which have led to the production of large samples, of dimensions 2-10 cm, of organic electro-optic materials. The perfection of these is defined. The influence of lattice imperfections on the evaluation of fundamental physical parameters related to electro-optic device behaviour is discussed. The materials produced by these methods are of a quality and performance suited to their use as commercial electro-optic devices.

43 citations


Journal ArticleDOI
TL;DR: In this paper, the authors developed a methodology for the measurement of quadratic nonlinear optical properties of crystals, mainly based on the use of the spherical geometry which allows, with only one crystal, accurate measurements of the phase-matching directions and the associated angular acceptances, double-refraction angles and effective coefficients.
Abstract: We develop a methodology for the measurement of quadratic nonlinear optical properties of crystals. Our methods are mainly based on the use of the spherical geometry which allows, with only one crystal, accurate measurements of the phase-matching directions and the associated angular acceptances, double-refraction angles and effective coefficients. These data constitute a reliable basis for the modelling of the second-order electric susceptibility of crystals and for the comparison between materials.

40 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of apodization of a generalized holographic axicon that produces a uniform axial line intensity distribution are considered, both by simulations and experimentally, and it is shown that the apoization considerably improves the image line quality within the extended focal region, especially near the image end points.
Abstract: The effects of apodization of a generalized holographic axicon that produces a uniform axial line intensity distribution are considered. It is shown, both by simulations and experimentally, that the apodization considerably improves the image line quality within the extended focal region, especially near the image end points. A simple method of implementing the apodization by a binary-amplitude encoding of the generalized axicon is assessed in detail. Fabrication of the axicon by photoreduction and experimental results on the intensity variations of the line image, which are in substantial agreement with the theoretical considerations, are presented and analysed. On apodization the axial intensity becomes nearly uniform, while transversely the line image retains its high definition.

39 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe optical linear and nonlinear properties of layered materials which follow a suitable process to realize a self-similar or fractal structure, which is very interesting.
Abstract: Composites are an important class of optical materials for use in nonlinear optics. Among them, layered materials are very interesting. In the present paper we describe optical linear and nonlinear properties of layered materials which follow a suitable process to realize a self-similar or fractal structure.

34 citations


Journal ArticleDOI
TL;DR: In this article, the use of an integrated optical Bragg-reflector as a chemo-optical sensor was described and it was shown that these types of Bragg reflectors for a wavelength of 630 nm can be realized with a bandwidth smaller than 0.2 nm in a optical channel waveguide.
Abstract: This paper describes the use of an integrated optical Bragg-reflector as a chemo-optical sensor. It is shown that these types of Bragg-reflectors for a wavelength of 630 nm can be realized with a bandwidth smaller than 0.2 nm in a optical channel waveguide. Measurements show that a refractive index change of the waveguide cladding of can be detected.

34 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed pure inorganic and hybrid organic-inorganic solids by sol-gel processing of silicon alkoxides, which can be obtained at room temperature, in any desired shape, including thin films, and are able to trap organic molecules or clusters.
Abstract: We have developed pure inorganic and hybrid organic-inorganic solids by sol-gel processing of silicon alkoxides. `Dense' gels are obtained at room temperature, in any desired shape, including thin films, and we are able to trap organic molecules or clusters. Gels can be polished and exhibit optical transmission in the visible range similar to that of high-temperature silica glasses. Concerning `gel-molecule' and `gel-nanocrystal' composites, the diversity of the organofunctional alkoxide precursors allows us to modify the optical properties by changing the nature and the strength of chemical and electronic interactions between the optically active guest system and the solid host matrix.

Journal ArticleDOI
TL;DR: In this article, the origins of the diffraction gratings or holograms induced by a light intensity pattern in a dye-doped nematic liquid crystal sandwiched between two conducting glass plates are described.
Abstract: This paper describes low-molecular-mass liquid crystals doped with suitable dyes which can be used for real-time holographic purposes We describe the origins of the diffraction gratings or holograms induced by a light intensity pattern in a dye-doped nematic liquid crystal sandwiched between two conducting glass plates The mechanism is linked to electric-field-driven reorientation of the nematic director The modulation of the electric field is induced mainly by the bulk photoconductivity of the system Design and characterization (response time, diffraction efficiency) of the optically addressed spatial light modulator (OA-SLM) is presented Interesting applications of these materials enabling phase conjugation and optical correlation are discussed

Journal ArticleDOI
TL;DR: In this article, a procedure for the determination of emission and absorption cross sections in integrated waveguides from transversal fluorescence spectra is presented based on an approximate treatment of McCumber's theory, which was demonstrated to provide accurate values for -doped silica fibres.
Abstract: A procedure for the determination of emission and absorption cross sections in integrated waveguides from transversal fluorescence spectra is presented. It is based on an approximate treatment of McCumber's theory, which was demonstrated to provide accurate values for -doped silica fibres. Results on the transition of in waveguides pumped by a 980 nm laser diode are shown and compared to results from attenuation measurements. Advantages over other procedures for waveguide characterization (less dependence on experimental inaccuracies, all measurements are made on the waveguide, consideration of codoping influence and no pump interference around ) are discussed in detail.

Journal ArticleDOI
TL;DR: In this paper, an application of the original Hartmann method to bundles of rays generated by a Shack-Hartmann analyser is considered. But the authors consider the case when the wavefront asphericity is so strong that real subimages produced by individual lenslets of the array are no longer simultaneously focused at a common plane.
Abstract: We consider an application of the original Hartmann method to bundles of rays generated by a Shack-Hartmann analyser. Absolute Shack-Hartmann measurements of converging wavefronts with the nominal method of collimating optics, used to locate the real image of a pupil on a microlens array, are not applicable when the wavefront asphericity is so strong that real subimages produced by individual lenslets of the array are no longer simultaneously focused at a common plane. As examples of strongly aspherical wavefronts we consider reflected beams obtained when testing large aspherical mirrors at their centre of curvature. Analytic formulae are applied to several instances and a ray-tracing program for a large-diameter strongly paraboloidal liquid mirror suggests that the Shack-Hartmann method could, however, be used by combining several cross sections of interlaced rays located downstream from the microlens array. In order to estimate how precisely subbundles of rays may be reconstructed from several cross sections we performed a small-scale experiment to measure an aspherical wavefront departing by more than from a best-fit sphere. A microlens array samples 2000 subareas per pupil. Eleven cross sections, corresponding to as many real and virtual subbundles of rays, are obtained upstream and downstream from an array using a relay optics to give enlarged real images on photographic film. We measured 57 subbundles and verified the straight line propagation of light to within a precision on negatives corresponding to a local 45 nm wavefront uncertainty. The uncertainty value for calibration using additional cross sections upstream and downstream from the microlens array amounts to 8 nm. We conclude from these numerical and practical experiments that the Shack-Hartmann method may be modified in order to measure strongly aspherical wavefronts, including reflected wavefronts obtained from centre-of-curvature testing for large aspheric mirrors.

Journal ArticleDOI
TL;DR: In this article, exact and asymptotic results for the electromagnetic field inside a dielectric slab in terms of the given field or source current outside the slab were given.
Abstract: We present exact and asymptotic results for the electromagnetic field inside a dielectric slab in terms of the given field or source current outside the slab. Exact results for the reflected and transmitted fields are also given. In particular, we provide explicit exact and asymptotic results for the case in which the incident wave is a converging electromagnetic wave generated by a time-harmonic aperture current. In a separate paper our results are used to obtain exact and asymptotic numerical results for the focused field inside the slab.

Journal ArticleDOI
Heike Bach1
TL;DR: In this article, a project was conducted for the State Ministry for Rural Environment, Food, and Forestry of Baden-Wurttemberg (Germany) to more accurately estimate agricultural yield.
Abstract: In order to test remote sensing data with advanced yield formation models for accuracy and timeliness of yield estimation of corn, a project was conducted for the State Ministry for Rural Environment, Food, and Forestry of Baden-Wurttemberg (Germany). This project was carried out during the course of the `Special Yield Estimation', a regular procedure conducted for the European Union, to more accurately estimate agricultural yield. The methodology employed uses field-based plant parameter estimation from atmospherically corrected multitemporal/multispectral LANDSAT-TM data. An agrometeorological plant-production-model is used for yield prediction. Based solely on four LANDSAT-derived estimates (between May and August) and daily meteorological data, the grain yield of corn fields was determined for 1995. The modelled yields were compared with results gathered independently within the Special Yield Estimation for 23 test fields in the upper Rhine valley. The agreement between LANDSAT-based estimates (six weeks before harvest) and Special Yield Estimation (at harvest) shows a relative error of 2.3%. The comparison of the results for single fields shows that six weeks before harvest, the grain yield of corn was estimated with a mean relative accuracy of 13% using satellite information. The presented methodology can be transferred to other crops and geographical regions. For future applications hyperspectral sensors show great potential to further enhance the results for yield prediction with remote sensing.

Journal ArticleDOI
TL;DR: In this paper, the phase conjugation in polystyrene films containing the commercially available azobenzene dye Disperse Red 1 was measured using CW laser radiation generated by a frequency-doubled YAG laser of total power 50 mW.
Abstract: Optical phase conjugation in polystyrene films containing the commercially available azobenzene dye Disperse Red 1 was measured using CW laser radiation generated by a frequency-doubled YAG laser of total power 50 mW The degenerate four-wave mixing (DFWM) experiment allowed for measurement of the build-up time of the phase-conjugate signal and phase-conjugate reflectivity as a function of dye concentration and input beam intensities The phase-conjugate reflectivities reached 01% in polystyrene films containing 25 wt% of the dye, with the phase-conjugate signal build-up time constants amounting to about 100 ms The appearance of a phase-conjugate signal is linked with a build-up of absorption-induced gratings of a mixed (phase and amplitude) nature Interesting thermally induced effects such as lensing effects and nonlinear chaotic behaviour of the phase-conjugate signal were observed

Journal ArticleDOI
TL;DR: In this article, a comparison procedure based on two low-order measured fractional moments is described and tested by utilizing Monte Carlo samples from three distributions commonly used in atmospheric propagation (Ln, LnME and K).
Abstract: Use of moments of non-integer order (called fractional moments) in statistical optics is proposed for discriminating between candidates for probability density functions (PDFs) of the scintillation intensity to overcome the experimental problems encountered by using integer moments. Low-order (< 2) fractional moments allow comparison of experimental data with theoretical PDFs of the intensity in different scintillation regimes. A comparison procedure, based on two low-order measured fractional moments, is described and tested by utilizing Monte Carlo samples from three distributions commonly used in atmospheric propagation (Ln, LnME and K). The bin width required to discriminate between different distributions and the effect of noise are investigated. Examples of application to experimental data are presented.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that, for a fixed pulse width, there is a broad interval of values of the pulse's peak power in which TOD stabilizes the transmission, in particular when the mean second dispersion is (weakly) normal, and when TOD suppresses strong internal vibrations of the non-fundamental soliton.
Abstract: By means of systematic numerical simulations of pulse (soliton) transmission through a very long nearly dispersion-compensated nonlinear fibre link, including third-order dispersion (TOD), we demonstrate that, for a fixed pulse width, there is a broad interval of values of the pulse's peak power in which TOD stabilizes the transmission. In particular, TOD prevents decay of the pulse in the case when the mean second dispersion is (weakly) normal, , and in the case where , TOD suppresses strong internal vibrations of the non-fundamental soliton, making it close to the fundamental one.

Journal ArticleDOI
TL;DR: In this paper, a generalized source method is presented for the resolution of the problem of monochromatic wave propagation in non-homogeneous, isotropic structures, which can be implemented in the form of an iterative technique to give the exact analytical solution of the known problem of propagation in a two half-space structure.
Abstract: A generalized source method is presented for the resolution of the problem of monochromatic wave propagation in non-homogeneous, isotropic structures When implemented in the form of an iterative technique, it is demonstrated to give the exact analytical solution of the known problem of propagation in a two half-space structure When implemented in the form of an integral expression, it is shown to give an exact solution under a normalized numerical convergence criterion It thus represents a new powerful method for electromagnetic wave propagation in arbitrary structures, and also for the assessment of other resolution techniques proposed so far in optical wave propagation, diffraction and scattering

Journal ArticleDOI
TL;DR: In this paper, a remote sensing technique using a commercial moderate-resolution Fourier-transform infrared spectrometer was used to examine emissions from operational natural gas flares, and the thermal radiation emitted by the post-combustion gas was analyzed to determine plume temperatures and concentrations of and.
Abstract: Emissions from operational natural gas flares are examined by a remote sensing technique using a commercial moderate-resolution Fourier-transform infrared spectrometer. The thermal radiation emitted by the post-combustion gas is analysed to determine plume temperatures and concentrations of and . The multicomponent air pollution software (MAPS) is applied which is based on radiative transfer line-by-line calculations and least-squares fit procedures. Emission rates and combustion efficiencies are calculated which indicate that the local environmental impact of methane emissions from natural gas flares is small, while significant amounts of carbon dioxide are released.

Journal ArticleDOI
TL;DR: In this paper, the authors compare theoretical and experimental results for focusing two-dimensional electromagnetic waves through a plane interface and find that good agreement is found when account is taken of possible aberrations.
Abstract: We compare theoretical and experimental results for focusing of two-dimensional electromagnetic waves through a plane interface. In general, good agreement is found when account is taken of possible aberrations. However, when the relative refractive index between the two media becomes large, discrepancies are observed due to reflections from the back surface of the second medium.

Journal ArticleDOI
TL;DR: In this article, a phase step interferometry system using polarization shifting is described, which is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization travelling through the other arm.
Abstract: A phase step interferometry system using polarization shifting is described. The device is essentially a Mach-Zehnder interferometer in which the polarization of light travelling through one arm is orthogonal to the polarization of light travelling through the other arm. At the interferometer output we place a quarter-wave plate with its fast axis at with respect to the polarization directions and a polarizer. By rotating the polarizer, the interfering waves acquire an extra phase (of topological origin) to that expected from the calculations of optical path lengths, and thus, arbitrary phase shifts can be induced. Then, from a set of interferograms recorded while the reference phase is changed, the `dynamical' phase difference (e.g. the phase profile of an object placed in one of the interferometer arms) can be reconstructed by using techniques of phase-shifting interferometry.

Journal ArticleDOI
TL;DR: In this paper, a simple model accounting for all the observable parameters of all the known all-optical poling schemes for frequency conversion has been developed, which permits a good prediction of the poling dynamics.
Abstract: All-optical poling is based on the excitation of nonlinear molecules using dual-frequency beams. The process is optimized at a molecular level when the molecules are resonantly excited. From the point of view of frequency conversion applications, this raises the question of device transparency to the frequency-converted output. In order to treat this efficiency transparency tradeoff, we recently developed a simple model accounting for all the observable parameters. The model permits a good prediction of the poling dynamics. Its self-consistency permits the description of all the known all-optical poling schemes. In particular, analysis of the parameters of the model permits the identification of new strategies towards the realization of stable and transparent phase-matched materials for frequency conversion. Some preliminary experimental results are presented in this respect.

Journal ArticleDOI
TL;DR: In this article, the focusing of two-dimensional (2D) electromagnetic waves through a plane interface was studied and the exact solution for the transmitted field due to an arbitrary 3D incident wave was derived in the Kirchhoff approximation.
Abstract: We study the focusing of two-dimensional (2D) electromagnetic waves through a plane interface. Starting from the exact solution for the transmitted field due to an arbitrary three-dimensional (3D) incident wave, we derive solutions for focused 3D waves in the Kirchhoff approximation. Then we construct corresponding solutions for focused 2D electromagnetic waves and study in detail the focusing properties of a TM field numerically and analytically.

Journal ArticleDOI
TL;DR: In this paper, a high-precision digital automated quantitative determination of the modulus of the complex degree of coherence was proposed, using a CCD and a measurement method based on the fast Fourier transform.
Abstract: We propose a high-precision digital automated quantitative determination of the modulus of the complex degree of coherence. The Thompson and Wolf experiment is repeated, using a CCD and a measurement method based on the fast Fourier transform. The experimental results agree very well with the predictions of the theory.

Journal ArticleDOI
TL;DR: In this paper, the integrable forms of the ICNLS equation are identified from the Painleve singularity structure analysis, and variable transformations which connect integrably forms of ICNs and coupled nonlinear Schrodinger equations (CNLS) are presented.
Abstract: The inhomogeneous coupled nonlinear Schrodinger (ICNLS) equations which describe the propagation of two fields in a nonuniform fibre medium are considered. The integrable forms of the ICNLS equation are identified from the Painleve singularity structure analysis. The variable transformations which connect the integrable forms of the ICNLS equation and the coupled nonlinear Schrodinger equations (CNLS) are presented. With the help of the linear eigenvalue problem and Backlund transformation, a single-soliton solution is generated explicitly.

Journal ArticleDOI
TL;DR: In this article, the authors studied the propagation characteristics of focused, apertured radially symmetric beams and showed that the axial point at which the mean-square radius of the diffracted beam is a minimum tends to be displaced towards the aperture plane depending on the Fresnel number associated with the aperture and the radius of an incident beam.
Abstract: We study the propagation characteristics of focused, apertured radially symmetric beams and show that the axial point at which the mean-square radius of the diffracted beam is a minimum tends to be displaced towards the aperture plane depending on the Fresnel number associated with the aperture and the Fresnel number associated with the radius of the incident beam. The magnitude of this effect can be determined by a simple and general formula in terms of the amplitude distribution of the incident beam across the aperture and of the two Fresnel numbers. We investigate the focal shift effects for the case of a focused, apertured Gaussian beam. The irradiance and the encircled-power distributions in the plane at which the mean-square radius of the diffracted beam is minimum are calculated and compared with those corresponding to a uniform beam.

Journal ArticleDOI
TL;DR: In this article, a supramolecular synthesis utilizing perhydrotriphenylene (PHTP) as an inclusion host compound has proven to be an efficient method of aligning guest nonlinear optical (NLO) molecules in a parallel fashion.
Abstract: A supramolecular synthesis utilizing perhydrotriphenylene (PHTP) as an inclusion host compound has proven to be an efficient method of aligning guest nonlinear optical (NLO) molecules in a parallel fashion. Application of Markov's theory of stochastic processes explains successfully the experimentally observed spontaneous formation of polarity on a macroscopic level.

Journal ArticleDOI
TL;DR: In this article, the formation of spontaneous gratings induced by a polarized laser beam in thin photosensitive AgCl waveguide films, doped by Ag, was studied by means of small-angle scattering.
Abstract: The formation of spontaneous gratings induced by a polarized laser beam in thin photosensitive AgCl waveguide films, doped by Ag, was studied by means of small-angle scattering. It is shown that small-angle scattering is determined by the domain structure of the spontaneous gratings and arises because of the re-emission of waveguide modes by neighbouring domains. The instability and reorganization of the gratings have been found and studied upon the change of the azimuth of the laser beam polarization.