Showing papers in "Pure and Applied Optics: Journal of The European Optical Society Part A in 1997"
TL;DR: In this article, the authors report on their activities in design, fabrication, characterization and system integration of refractive microlens arrays for sensors and microsystems, including neural networks and multiple pupil imaging systems for photolithography.
Abstract: We report on our activities in design, fabrication, characterization and system integration of refractive microlens arrays for sensors and microsystems. Examples for chemical analysis systems (, blood gas sensor), neural networks and multiple pupil imaging systems for photolithography (microlens and smart mask lithography) are presented.
416 citations
TL;DR: In this paper, simple expressions for the Stokes parameters of light emerging from either arm of an arbitrary interferometer, and of light in the interference field are given in terms of the incident polarization and involve four axes, determined by the interferometers, on the Poincare sphere.
Abstract: On exprime de facon simple les parametres de Stokes des lumieres emergentes de chaque voie d'un interferometre quelconque isolement, et de la lumiere emergente dans le champ d'interferences; ils sont donnes en fonction de la polarisation incidente, a l'aide de ses coordonnees dans l'espace de la sphere de Poincare sur quatre axes determines par l'interferometre. Si les deux voies ne sont pas dichroiques, ces expressions se simplifient encore. On examine les effets d'une variation du dephasage entre les voies, et on compare avec le cas scalaire. Enfin, on etudie des cas d'interferences de polarisation pures (i.e. sans interferences au sens de l'amplitude): on indique des idees d'experiences ou les `franges' d'interferences se traduisent seulement par des gradients des trois caracteristiques de la polarisation successivement (degre de polarisation, ellipticite, et orientation). Simple expressions are given for the Stokes parameters of light emerging from either arm of an arbitrary interferometer, and of light in the interference field; they are given in terms of the incident polarization and involve four axes, determined by the interferometer, on the Poincare sphere. For interferometers with non-dichroic arms, these expressions become even simpler. The effect of a variable path between the two arms is examined in comparison with the scalar case. Finally, pure polarization state interference, as opposed to amplitude interference, is investigated: some experiments are suggested to obtain interference `fringes' that manifest themselves only as gradients of three usual parameters of polarization (degree of polarization, ellipticity and orientation).
78 citations
TL;DR: In this paper, a fabrication technology for the creation of high-aperture polymer microlenses and their optical characterization both as single lenses and mounted in a microobjective is presented.
Abstract: We present a fabrication technology for the creation of high-aperture polymer microlenses and their optical characterization both as single lenses and mounted in a micro-objective. The microlenses are made by the LIGA process (x-ray lithography, electroforming and moulding techniques), which is modified by an additional x-ray irradiation step and a melting process. The spherical lenses are realized by melting of PMMA micro-cylinders, which have been flood exposed in the additional synchrotron irradiation step. For the cost-effective replication by hot embossing a moulding tool is made out of the primary PMMA lenses. As the focus of interest is the development of a micro-objective for medical applications, we concentrated on lenses which have a front focal length of 700 and and an equal outer diameter of , which is achieved by an additional lateral structuring.
64 citations
TL;DR: In this paper, the Backlund transformation for the coupled NLS equations and coupled Hirota equations is constructed, and the explicit one-soliton solution is constructed. And in this paper, we consider the two orthogonally polarized wave propagations in the nonlinear modal birefringent fiber governed by the coupled nonlinear Schrodinger type equations.
Abstract: We consider the two orthogonally polarized wave propagations in the nonlinear modal birefringent fibre governed by the coupled nonlinear Schrodinger type equations. In this letter, we construct the Backlund transformation for the coupled NLS equations and coupled Hirota equations. The explicit one-soliton solution is constructed.
43 citations
TL;DR: In this paper, the diffusion mechanism for hologram formation in multicomponent polymerizable systems undergoing photocrosslinking was examined and the nonlinear diffusion equation was solved to predict the behaviour of the recording system.
Abstract: The diffusion mechanism for hologram formation in multicomponent polymerizable systems undergoing photocrosslinking was examined. The nonlinear diffusion equation was solved to predict the behaviour of the recording system. The results show the crucial importance of the competition between diffusion and photochemical reaction. They account for the reciprocity failure and nonlinearity and reveal the interdependence of the physicochemical, optical and photonic parameters. The experimental results obtained with a model recording system are in better than qualitative agreement with this theoretical approach.
40 citations
TL;DR: In this article, the optical properties in both monoclinic and triclinic forms of ClAlPc were reported, and a direct allowed transition at 3.05 eV was observed.
Abstract: Thin films of ClAlPc of 100 - 300 nm thickness were sublimed onto glass substrates in high vacuum. Studies of the molecular structure of ClAlPc have been made using films deposited at various temperatures and films annealed after deposition at room temperature. The optical properties in both monoclinic and triclinic forms are reported. Optical data have been obtained from both absorption and reflectivity spectra over the wavelength range 350 - 800 nm. Monoclinic films show two absorption bands, an exciton absorption on the low-energy side of the transparent band and a fundamental absorption above 2.55 eV. A direct allowed transition at 3.05 eV was observed. A doublet of energies in the absorption spectra of the monoclinic form at 1.74 and 1.9 eV was also observed in good agreement with previous findings for other metal phthalocyanines, including CuPc, PbPc, NiPc and CoPc.
39 citations
TL;DR: In this paper, the case of interference with two partially coherent time Gaussian-shaped pulsed point sources is discussed, and a criterion for the measurement of spatial coherence of nonstationary sources is given.
Abstract: Loeve's theory of harmonizable stochastic processes, and in particular their spectral representation, is used to describe the light from nonstationary sources. After introducing the general formalism and basic relations, the case of interference with two partially coherent time Gaussian-shaped pulsed point sources is discussed, and a criterion for the measurement of spatial coherence of nonstationary sources is given.
37 citations
TL;DR: In this article, different types of microlens arrays consisting of extremely non-spherical elements have been produced with thin-film deposition methods, and specific spatial transformation characteristics can be used for applications in the fields of laser material processing, optical sensing and measuring techniques.
Abstract: Different types of microlens arrays consisting of extremely non-spherical elements have been produced with thin-film deposition methods. structures with pitches of and element numbers of up to have been deposited on rigid quartz and flexible polycarbonate substrates. Axial and radial beam shaping has been investigated theoretically as well as experimentally for selected geometries (Gaussian and double-parabolic profiles, pitch). Oscillating intensity distributions, in particular extended and multiple foci, have been generated by Gaussian-like and double-parabolic phase functions. The specific spatial transformation characteristics can be used for applications in the fields of laser material processing, optical sensing and measuring techniques. Fibre coupling and collimation with non-spherical microlenses have been demonstrated.
34 citations
TL;DR: In this paper, a combination of micro-optical elements having different optical functions in the same array has been used for direct laser beam writing, which is a mature technology for the fabrication of continuous-relief micro-lens and lens arrays having a wide range of different optical design parameters.
Abstract: Direct laser beam writing is a mature technology for the fabrication of continuous-relief micro-optical (diffractive and refractive) lenses and lens arrays having a wide range of different optical design parameters. Whereas most microlens array applications require only one specific element type, some applications can profit from the combination of micro-optical elements having different optical functions in the same array. Lens arrays with a spatial variation of the focal length and beam deflection angle have been fabricated and successfully tested in confocal microscope measurements on non-planar surfaces.
27 citations
TL;DR: In this article, the authors compare the Debye and Kirchhoff approximations for focusing of electromagnetic waves, with special emphasis on the focusing of converging electric-dipole waves.
Abstract: We compare the Debye and Kirchhoff approximations for focusing of electromagnetic waves, with special emphasis on the focusing of converging electric-dipole waves. Numerical solutions for the spectral amplitude of the incident converging wave and for the focused field are provided in both approximations for a variety of Fresnel numbers and f-numbers. Comparisons of numerical solutions in Kirchhoff and Debye approximations show that for systems of Fresnel numbers larger than 20 and f-numbers less than 0.5, both approximations give indistinguishable results for focused electric-dipole waves. At low Fresnel numbers, the Kirchhoff approximation gives the best results irrespective of the f-number, as in the scalar case. The focal shift depends mainly on the Fresnel number, but at low Fresnel numbers, a reduction of the f-number gives an increase of the relative focal shift.
25 citations
TL;DR: In this paper, the dependence of the metal cluster plasmon resonance position on the silicon film thickness has been established, and the inhomogeneous broadening of the PLASM line has been estimated.
Abstract: Silver and indium nanoclusters have been incorporated into thin sputtered amorphous silicon films. The optical properties of these films have been investigated and compared with the results of spectra simulations. The dependence of the metal cluster plasmon resonance position on the silicon film thickness has been established. Additionally, the inhomogeneous broadening of the plasmon line has been estimated. The data are discussed with respect to the results of transmission electron microscopy.
TL;DR: In this paper, the synthesis and nonlinear optical characterization of highly soluble Ni-, Pd- and Pt-phthalocyanines is reported, and the imaginary part of the nonlinear susceptibility was observed at 665 nm.
Abstract: The synthesis and nonlinear optical characterization of highly soluble Ni-, Pd- and Pt-phthalocyanines is reported. When excited resonantly within the Q-band, the third-order nonlinearity is dominated by saturable absorption, observed using the z-scan technique. The imaginary part of the nonlinear susceptibility was observed at 665 nm. From a three-level model, ground-state recovery times in the picosecond regime were determined for all phthalocyanines studied. These fast recovery times were supported by time-resolved measurements using degenerate four-wave mixing in the phase-conjugate geometry.
TL;DR: In this article, a method based on the properties of local correlation of speckle patterns, scattered by the surface when it is illuminated by a laser, is used for in situ evaluation of the state of conservation of mural frescoes.
Abstract: A method based on the properties of local correlation of speckle patterns, scattered by the surface when it is illuminated by a laser, is used for in situ evaluation of the state of conservation of mural frescoes. Some experimental results are presented.
TL;DR: In this article, the authors discuss focusing of two-dimensional and three-dimensional scalar wave at low Fresnel numbers in the presence of cylindrical or spherical aberration.
Abstract: In this paper we discuss focusing of two-dimensional and three-dimensional scalar waves at low Fresnel numbers in the presence of cylindrical or spherical aberration. We show that a larger maximum axial intensity than in the aberration-free case can be obtained with a positive cylindrical or spherical aberration. Also, we give a physical explanation of this unexpected result.
TL;DR: In this paper, an algorithm to treat an experimental Mueller matrix based on the knowledge of the measurement errors, and connected to the study of the depolarization effects in the Poincare space, allows us to characterize and classify any optical system.
Abstract: The polarizing and depolarizing properties of an optical system can be derived from the experimental determination of its Mueller matrix. Constructing an algorithm to treat an experimental Mueller matrix based on the knowledge of the measurement errors, and connected to the study of the depolarization effects in the Poincare space, allows us to characterize and classify any optical system. Different samples of materials and surfaces are analysed by this method while polarimetric image coding provides the spatial distribution of the depolarization for each target.
TL;DR: In this article, the diffraction characteristics of a time Gaussian-shaped source in diffraction from a rectangular aperture are investigated theoretically, and it is pointed out that if the proportionality in the Fresnel diffraction integral is neglected as by Sereda et al., the results obtained are not accurate.
Abstract: The diffraction characteristics of a time Gaussian-shaped source in diffraction from a rectangular aperture are investigated theoretically. It is pointed out that if the proportionality in the Fresnel diffraction integral is neglected as by Sereda et al, the results obtained are not accurate.
TL;DR: In this paper, the dispersion law for eigen circularly polarized light waves propagating at an angle with respect to the axis of periodicity of the medium is investigated, and the characteristics of reflected and transmitted light waves at oblique incidence in resonant and non-resonant cases are obtained.
Abstract: Features of the interaction of light with a periodic bi-gyrotropic medium are investigated. The dispersion law for eigen circularly polarized waves propagating at an angle with respect to the axis of periodicity of the medium is found. The characteristics of reflected and transmitted light waves at oblique incidence in resonant and non-resonant cases are obtained.
TL;DR: In this article, an analysis of fractional-order derivatives of two-dimensional (2D) phase objects is given in terms of the Fourier transform which suggests its optical implementation using Fourier optics techniques.
Abstract: This paper contains an analysis of fractional-order derivatives of two-dimensional (2D) phase objects. The expression for noninteger-order 2D derivatives is given in terms of the Fourier transform which suggests its optical implementation using Fourier optics techniques. We propose an oblique illumination geometry of a 4f correlator to achieve real Fourier plane differentiating filters. In computer simulations, we prove that only in the case of the semiderivative filter, the output intensity is directly proportional to the first derivative of an input phase object. Thus, the semiderivative filter allows exact visualization of phase changes. We show experimental results of differentiation with the first- and -order derivative real filters.
TL;DR: In this paper, an optical fiber delay line with a total stroke of 2.04 m has been tested in a Mach - Zehnder interferometer in the spectral domain.
Abstract: We report the implementation of an optical fibre delay line demonstrating the capability of stretched silica fibre to induce a large and variable group delay. A metric delay line with a total stroke of 2.04 m has been tested in a Mach - Zehnder interferometer in the spectral domain. The induced waveguide losses are very low. At the present time the polarization and the dispersion effects are not corrected.
TL;DR: This work designs and is currently constructing a recurrent neural network with fully interconnected channels and an optical feedback loop for illumination, imaging and fan-in using diffractive microlens arrays instead of bulk achromats.
Abstract: We have designed and are currently constructing a recurrent neural network with fully interconnected channels and an optical feedback loop. We have mainly used diffractive microlens arrays instead of bulk achromats for illumination, imaging and fan-in. We report on the advantages of this approach, design considerations and first experimental results with various original and replicated microlens arrays.
TL;DR: In this article, the authors studied the focusing properties of converging mixed-dipole wave for the case in which the two dipoles are orthogonal, and they showed that the converging electric and magnetic dipoles give indistinguishable electric and total energy distributions around the focus.
Abstract: A converging mixed-dipole wave is defined as the sum of a converging electric-dipole wave and a converging magnetic-dipole wave. In this paper we study the focusing properties of converging mixed-dipole waves for the case in which the two dipoles are orthogonal. Within the Debye approximation, we compare both analytical and numerical results for the converging mixed-dipole wave with those of the converging electric-dipole wave and also with the results obtained when a linearly polarized plane wave is focused by a rotationally symmetric, aplanatic system. At large angular apertures, the converging electric-dipole wave is shown to give best electric-energy concentration and least cross-polarization, both in the focal plane and along the optical axis. At angular half-apertures less than , the three types of converging waves give indistinguishable electric and total energy distributions around the focus. In applications in which one wishes to maximize the electric energy density and/or minimize the cross-polarization the converging electric-dipole wave is the natural choice as the incident wave.
TL;DR: In this article, coupled Maxwell nonlinear equations for focused beam propagation are solved numerically to describe the cascade single-pass Stokes conversion (stimulated Raman scattering and four-wave mixing) in a high Raman gain molecular medium.
Abstract: The coupled Maxwell nonlinear equations for focused beam propagation are solved numerically to describe the cascade single-pass Stokes conversion (stimulated Raman scattering and four-wave mixing) in a high Raman gain molecular medium. A steady-state paraxial description is assumed, with a gain reduction parameter which approximates transient effects. The importance of the four-wave mixing averaging effect on the Stokes energy spectrum is shown. A parametric study is conducted in which the focusing lens focal length, the type and partial pressure of the Raman-active gas and of added rare gas, and the quality of the pump beam, are varied. The conversion efficiency and beam quality of the Stokes and anti-Stokes spectrum are computed. Four-wave mixing is shown to degrade the beam profile, the effect of which is most pronounced for the higher Stokes. Beam cleanup (i.e. the decrease of the parameter of the Stokes beam compared to the pump beam) occurs at low gain (i.e. before the intensity averaging regime appears), whereas it is the opposite case at high gain. The main qualitative features of the modelling match previously published experimental data well, and help to explain the commonalities and discrepancies between the results of different experimental set-ups.
TL;DR: In this paper, the authors study a variety of low f-number refractive microlenses and characterize each in terms of its scalar as well as its electromagnetic diffraction PSF using the combined method of raytracing and diffraction (CMRD).
Abstract: Scalar diffraction theories are often used to characterize optical imaging systems in terms of their scalar diffraction point-spread functions (PSFs). This works well at large f-numbers (low numerical apertures (NA)), since polarization effects can then be ignored. But as the f-number decreases, polarization effects become more important and a fully vectorial diffraction theory is required to determine the electromagnetic diffraction PSF of the system. In this paper we study a variety of low f-number refractive microlenses and characterize each in terms of its scalar as well as its electromagnetic diffraction PSF using the combined method of raytracing and diffraction (CMRD). We find that a polynomial aspherical surface gives less spherical aberration than a spherical or ellipsoidal surface. For the polynomial surface both the scalar and the electromagnetic PSFs are found to be asymmetric about the focal plane and to give focal shifts due to high-order spherical aberrations. The differences between scalar and electromagnetic diffraction PSFs are found to be small on the axis, due to symmetry, but for an f-number of 0.39, differences of up to are found off-axis.
TL;DR: In this paper, a novel process has been developed for the fabrication of dry-etch masks capable of defining diffractive structures in quartz, which is suitable for submicron optics and avoids process repeatability problems often encountered in fabrication procedures involving metallization followed by lift-off or wet etching.
Abstract: A novel process has been developed for the fabrication of dry-etch masks capable of defining diffractive structures in quartz. Shipley S1805 and UVIII photoresists have been patterned by electron beam lithography to exploit the high dry-etch resistance of photoresist and the attributes of electron beam lithography. The yield, linewidth fidelity, uniformity, verticality and resolution of the diffractive structures demonstrate that the process is suitable for submicron optics and avoids process repeatability problems often encountered in fabrication procedures involving metallization followed by lift-off or wet etching.
TL;DR: The compound eyes of insects and crustaceans are image-forming arrays of up to 30 000 microlenses as mentioned in this paper, which make use of both curved surface and graded refractive index optics, and in certain crustacea the lenses are replaced by radial mirrors or lens combinations.
Abstract: The compound eyes of insects and crustaceans are image-forming arrays of up to 30 000 microlenses. There are basically two types of design. In apposition eyes the overall erect image is made up from the centres of the small inverted images produced by each element in the array. However, in superposition eyes the ray paths from many elements combine optically to give a real erect image on the retina. The microlenses themselves make use of both curved surface and graded refractive index optics, and in certain crustacea the lenses are replaced by radial mirrors or lens - mirror combinations.
TL;DR: In this article, the effect of atmospheric turbulence on the imaging of scenes, for horizontal propagation of the light over a distance of 20 km, 15 m above the sea surface, was analyzed at visible wavelengths using a 20 cm telescope.
Abstract: The effect of atmospheric turbulence on the imaging of scenes, for horizontal propagation of the light over a distance of 20 km, 15 m above the sea surface, was analysed at visible wavelengths using a 20 cm telescope. Point-source images were recorded during the night, and the Fried parameter was derived using several methods, leading to values ranging from 2 to 4 cm depending on observing conditions. A very high level of scintillation was observed. Studies of correlations between close-by sources lead to a very small domain of isoplanatism. Daytime observations of an extended source are also performed; an image motion of small spatial coherent length seems to be drawn by a horizontal wind producing a wave-like distortion of horizontal lines and a boiling-like distortion of vertical ones.
TL;DR: In this paper, a new fabrication technique is presented to simplify the fabrication process of multilevel diffractive optical elements, based on a single optical lithography step and a subsequent dry-etching process.
Abstract: To simplify the fabrication process of multilevel diffractive optical elements a new fabrication technique is presented. The fabrication process is based on a single optical lithography step and a subsequent dry-etching process. Lateral structures with dimensions of 180 nm were transferred. The fabricated diffractive optical elements show high optical performance with diffraction efficiencies of over 90%.
TL;DR: In this article, an expression was derived to determine the refractive index profile of a graded index (GRIN) optical fiber using and, which considers the area enclosed under the interference fringe shift when using a liquid of this article exactly matching the cladding one.
Abstract: An expression has been derived to determine the refractive index profile of a graded index (GRIN) optical fibre using and . This expression considers the area enclosed under the interference fringe shift when using a liquid of refractive index exactly matching the cladding one. Multiple-beam Fizeau fringes are used to obtain the profile shape constant and the refractive index difference between the fibre centre and its cladding. Another two methods are applied to compare the results. The suggested method has the advantage that it gives the exact solution and it provides a simple relation between the measured quantities.
TL;DR: Theoretical, numerical and experimental results are given in this article to demonstrate the limitations of the fractional Talbot effect for array illuminators and their application in microlens arrays.
Abstract: The Talbot effect which also appears for the foci of microlens arrays can, in principle, be used for array illuminators. In particular, the multiplication of the foci in the fractional Talbot planes seems to be promising. Certainly, in practice there are three effects which limit the application of the fractional Talbot effect for microlens arrays. Theoretical, numerical and experimental results are given to demonstrate these limitations.
TL;DR: In this article, the method of curvilinear coordinates is formulated using the coordinate transformations given by parametric equations, and a translation coordinate system and a relaxation coordinate system are used to calculate the reflectivities of various cycloidal profiles.
Abstract: La methode des coordonnees curvilignes est formulee dans le cas ou le changement de coordonnees est donne par des equations parametriques. A titre d'illustration, un systeme de coordonnees de translation et un autre de relaxation sont utilises pour calculer les efficacites de quelques reseaux a profil cycloidal. On montre sur cet exemple que les systemes de coordonnees parametriques permettent de traiter des profils auparavant inaccessibles parce que trop pointus. The method of curvilinear coordinates is formulated using the coordinate transformations given by parametric equations. As an illustration, a translation coordinate system and a relaxation coordinate system are used to calculate the reflectivities of various cycloidal profiles. We show, with this example, that parametric coordinate systems permit one to handle profiles that previously had been out of reach owing to their sharpness.