Archaeological mirrors from the Olmec civilization were analyzed in the context of a bibliography produced in the last two decades. Photographs of its images are shown as a proof of its good quality. Some suggestions are made on its probable utilization.

This paper begins with the argument that classical Fourier optical pattern recognition has passed from science to engineering and, hence, new directions in optical pattern recognition are needed. It then summarizes several of the new directions we are taking with the hope that this will stimulate others to introduce even more and/or refine ours.

Scintillation of waves is briefly reviewed, with particular attention to the problem of laser scintillation through atmospheric turbulence. An introductory description of turbulence, its model and relevant parameters, is given. Recent progress towards the solution of the problem of scintillation is reported, which includes modeling by means of numerical simulations and simultaneous measurements of both laser intensity fluctuations and all relevant parameters.

A review of the spectral and modulation characteristics of tunable DBR lasers is presented. The dependence of the linewidth and FM response on the nonuniform injection currents to the active sections and on the tuning currents to the passive sections of a four section DBR LD is investigated and a tradeoff between them is found. Some guidelines for the structure optimization are suggested.

We report on experiments in which alkali metals were probed in (commercial) hollow-cathode discharge lamps, using simple semiconductor diode lasers. A variety of spectroscopic techniques have been employed to demonstrate the versatility of the set-up, including Doppler- limited absorption, fluorescence and optogalvanic spectroscopies, and Doppler-free polarization spectroscopy.

A parametric optimization method is proposed to obtain the average values for the nonmeasurable quantities of inductance and resistance in the laser gas discharge and in the spark gap of a N₂ laser excited with a Blumlein circuit. The application of this method requires only the knowledge of the voltage waveform appearing on the laser electrodes and can be applied to any laser excited with a Blumlein or a C-to-C circuit.

We report a new achromatic Fourier processor constituted basically by a quasi wavelength- independent imaging forming system whose first half performs an achromatic Fourier transform of a color input object. Consequently, this optical architecture, formed by a small number of diffractive and refractive lenses, provides an intermediate achromatic real Fraunhofer plane and a final color image with a high signal-to-noise ratio. In this way, our optical processor can perform simultaneously the same spatial filtering operation for all the spectral components of the broadband illumination.

We compare two methods for optimizing the discrimination capability of phase only filter by designing a function of support. First, we study a method based on simulated annealing. Second, we propose a method in which we consider the correlations at the origin. The last one reduces very much the computing time. In all the cases we have studied, the proposed method arrives at better results than with simulated annealing.

A joint transform correlator of Weaver and Goodman modified to obtain teleobjective effects is considered. The structure to be processed consists of two rectangular displays (object and sample) and is placed between the classical converging optical system and the added diverging one. Since an adequate correlation signal is obtained when the aberrations in the object are equal to those in the sample, the correlator is designed in such a way that the difference between these aberrations is minimized.

The equations for the micromaser are derived without assuming the validity of the rotating- wave approximation (RWA) in the Scully-Lamb model for a single-mode maser off resonance. The treatment is based on Swain's continued fractions approach, by which the eigenvalues and eigenvectors of the Hamiltonian describing the system of atoms plus cavity field can be iteratively determined to any desired order and then used to obtain the micromaser equations. These are valid to second order in the parameter g, the coupling constant of the atom-field interaction. The procedure can be extended, to any desired order in g, by successive iterations. Through numerically evaluating the micromaser spectrum we compare our results with those of the RWA. We predict a relative shift, stemming from the Bloch-Siegert shift, which in case of the spectra corresponding to two-photon correlations should be measurable through atomic selective field ionization.

We present a numerical study of the temporal dynamics of a stimulated-Brillouin-scattering ring resonator. A coaxial-flashlamp-pumped RH6g dye laser is assumed. The influence of the most important parameters on the temporal evolution of the resonator is analyzed, namely the acoustic decay time of the nonlinear material, the features of the external-injection pulse--its pulsewidth, energy, and spatial quality--and the coupling mirror reflectivity. The conditions to initiate and sustain laser oscillation in the ring resonator as long as the duration of the pumping-system pulse persists were found.

This work presents the construction and characterization of a low-pressure, self-preionized nitrogen laser with capacitive charge transfer excitation circuit. The design has the advantage of allowing easy changes in all the parameters, either of the electric circuit or the discharge tube, to obtain different beam dimensions and output efficiencies. Also shown is the dependence of output pulse width and energy (1 mJ maximum without optical cavity) on pressure, charge and transfer capacities and the length, shape and separation of the electrodes. The electrical and optical measurements show a preionization of the discharge that explain the high stability obtained.

The method known as frequency-resolved optical gating for the retrieval of the electric field of an ultrashort pulse requires the use of an iterative algorithm. Here we show that using a computational neural network the pulse can be directly recovered.

We describe a technique for investigation of beam coupling in photorefractive materials. We used a probe beam which partly erases the recorded hologram in a small region of the crystal. This erasure changes the coupling between the beams, then the output intensities of these beams are changed. We show by numerical simulations that these changes give us information about coupling coefficient along the length of the photorefractive sample. We compare the numerical results with experimental data of two-beam coupling in an optical active BTO waveguide-like crystal.

Results on modifications to radiative corrections of an atomic dipole, in the vicinity of a phase-conjugate mirror (PCM), from the point of view of stochastic electrodynamics are presented. We show that the PCM can enhance or inhibit the real zero-point field. Also we discuss the existence of a 'Casimir-like' force, an interference pattern in the front of the mirror and a dynamical quadratic Stark-like effect in the atom.

The recent introduction of pulsed lasers for studying transient phenomena by means of TV holography makes very difficult the analysis of fringe patterns by conventional techniques. For this reason, previously to the evaluation of the phase distribution, digital filters must be applied to reduce speckle noise. In this paper some after fringe generation techniques for speckle noise reduction are compared: three methods commonly used in synthetic aperture radar imagery, a scale-space nonlinear filter and a de-noising method based on the use of wavelet transforms.

Two TV-holographic techniques to detect cracks in mechanical elements are demonstrated. One of them employs continuous illumination and is based in the modal analysis of the part. The other one consists in the study by pulsed TV-holography of transient waves induced in the part.

We have recorded in-plane displacements with speckle photography and out-of-plane displacements with holographic interferometry for solid bodies, from which the three- dimensional surface deformation can be determined. We demonstrate that it is possible to measure both uniform in-plane and out-of-plane displacements in one double-exposure hologram by reducing the reference-to-object-beam ratio to enhance speckle contrast in the hologram. We have also recorded the three-dimensional displacement of particles suspended in a fluid in a controlled experiment using holographic interferometry.

In this work is presented a multiplexing technique to produce color plane holograms using a single wavelength. A color digital scene is separated in its three basic colors by software. Each monochromatic scene generated with a PC computer is sending to a liquid crystal, which is used as a gray levels discrete transparency, and with a plane reference beam, previously calculated, a hologram is registered in the holographic film plate for each basic color.

In this paper we propose a technique to make numerical Fresnel holograms for binary and gray level objects, using Kirchhoff-Fresnel diffraction scalar theory in the paraxial approximation. These holograms produce a real image which can be observed in the reconstruction process with a He-Ne laser.

We modify the optical transfer function of an incoherent imaging system such that it is nearly invariant to misfocus and contains no zero values. Digital filtering of the resulting image restores the image to near diffraction limited spatial resolution. A system that is insensitive to misfocus is also insensitive to some lens aberrations. Consequently, the approach of combining optical and digital signal processing system extends the normal aberration balancing of lens design to include those aberrations that can be reduced by digital signal processing, such as spherical aberration.

Incoherent imaging quality of optical systems will depend on the properties of the OTF. In the current paper we show an OTF-based image quality analysis, in which the properties of the OTF are represented by means of matrices, whose components depend only on the centered reduced moments of measured PSFs. Quantitative descriptors of both the geometrical characteristics and the energy distribution of the PSF (i.e. position of centers of mass, length and orientation of semi-axis, eccentricities) are determined as functions of those components. So, different aberration types can be characterized by means of the OTF properties.

We propose to construct an arrangement of several spheres of Hindle, used like element optic assistants in order to prove mirrors convex hyperbolic of several characteristics, like that, their dimension is reduced.

We present Talbot array illuminators based on multilevel phase gratings that exhibit two bright zones for period. Our scheme is based in a matrix description for Fresnel diffraction of substructured gratings that allows us to foresee structural relationships between the diffractive element and its Fresnel wavefield.

In recent years laser spectroscopy has been gaining wider acceptance and use for analytical purposes, both in the laboratory and for practical applications. This is due to the improved technology of laser sources and detectors which have become reliable in operation, small in size and affordable in price. A few practical applications of spectroscopic methods are discussed for real-time, in-situ and remote analysis. Examples include the techniques of laser- induced breakdown spectroscopy (LIBS), laser-induced fluorescence (LIF), and laser-enhanced ionization (LEI).

We present a model of a nematic liquid crystal cell to describe the first and final stages of the reorientation process induced by the action of an obliquely incident optical field. The presence of hydrodynamic backflows associated with the reorientation in both, a homeotropic and a planar geometry, is explicitly taken into account. We study the effect produced by the backflows on two specific optical properties of the nematic, namely, its phase change and its inverse focal length. These quantities are calculated analytically and evaluated for the nematic phase of CBOOA. It is shown that for a homeotropic arrangement, hydrodynamic backflows may produce a significant, and in principle measurable, change as high as 75% in these properties.

The experimental data for the nonradiative energy transfer from Nd³⁺ to Er³⁺ in Nd(1%), Er(15%) : YAG and in Nd(1%), Er(30%) : YAG is reanalyzed. The nonradiative energy transfer is not driven by a single multipolar interaction, but by a quadrupole-quadrupole and a dipole-dipole interaction. These interactions compete to each other, for Nd - Er neighbor pairs the quadrupole-quadrupole overcomes the dipole-dipole interaction, and for pairs at further distances the effect is reversed. The critical transfer distance parameter is constant, that is, 8.65 angstrom and does depend on neither the kind of interaction nor concentration. Our analysis is based on Monte Carlo simulations which place dopants into the 24c sites of the YAG lattice and calculate the Nd³⁺ and Er³⁺ emission transients.

We present here a study of the Fraunhofer diffraction patterns produced by perfectly conducting surfaces that have a fractal profile of the Cantor bars type. The wavelength- minimum diffractive element ratio of this object is chosen in such a way that the scalar approximation for calculating the intensity distribution in the Fraunhofer plane is in principle no longer valid. We evaluate the diffraction pattern from both the FFT method and an electromagnetic vectorial method. The self-similarity features of the diffraction patterns obtained from these methods are calculated and the results are compared.

A study of the polarization of evanescent waves associated to internal total and inhibited reflection is done for ordinary and extraordinary incident wave on a uniaxial crystal-isotropic medium interface. It is shown that the field describe ellipses that are contained in planes that depend on the kind of evanescent wave. Furthermore the characteristics of the ellipses depend on the direction of incidence and/or on the direction of the optical axis. This behavior differs from that of isotropic interfaces.

In this work, we show that the classical dipolar model that explains the existence of Brewster angle in isotropic media can be extended to birefringent uniaxial crystals if we take into account the electric polarization.

We investigate the expression of non-Kolmogorov turbulence in terms of Zernike polynomials. Increasing the power-law exponent of the three-dimensional phase power spectrum from 2 to 4 results in a higher proportion of wavefront energy being contained in the tilt components. Closed-form expressions are given for the variances of the Zernike coefficients in this range. For exponents greater than 4, a von Karman spectrum is used to numerically compute the variances as a function of exponent for different outer-scale lengths. We find in this range that the Zernike-coefficient variances depend more strongly on outer scale than on exponent, and that longer outer-scale lengths lead to more energy in the tilt terms. The scaling of Zernike- coefficient variances with pupil diameter is an explicit function of the exponent.

Correlation methods for polychromatic range image recognition are presented. First, the range and the color are compared and the use of the hue images is discussed. The advantages and disadvantages in combining the range and the color information are analyzed. Single-channel and double-channel approaches are presented. The ability of both recognition methods to be invariant under translation in the xy plane and along the z axis are demonstrated. The codification of the range and the hue images using phase-coding, sine-coding and hybrid coding make possible the fully translation invariance. The double-channel is introduced using sine-coding images in the correlation process. Finally, the combination of those two channels is performed in order to improve the discrimination capability of the system. Digital results are shown.

We analyze the possibilities of white light interconnections by controlling the mixture of diffractive colors. In our experiments we used conventional holographic materials to reproduce the spatial frequency codification to obtain the desired color mixture. Experimental verifications are included.

Two multichannel configurations different from the conventional RGB channels are proposed to improve color discrimination in optical pattern recognition. One configuration consists of n narrow-band channels which are selected depending on the colors of the objects to discriminate. The other configuration applies a linear transformation on the RGB information based on the color human vision models. The proposed configurations are particularly advantageous when the colors of the objects belong to the same range of hue.

When a translucent rough surface is illuminated, light is diffused in different directions. The envelope the intensity distribution is called diffusion curve. As the diffuser is rotated with respect to the incident beam, the diffuser curve changes its appearance: the maximum suffers a displacement and changes its shape. Some authors have studied this phenomenon, but none of them explained it properly. In this work we make an additional contribution to address the problem, showing experimentally that the maximum displacement depends on the incident angle and the diffuser ratio T/(sigma) . We compare our experimental results with those that can be calculated with the reformulated Beckmann's theory. We could observe important agreements and differences. For example, Beckmann's theory predicts that the diffusion results are asymmetric, while our measured results are indefectibly symmetric.

In this work, we describe an experimental technique for synthesizing gratings with a periodic variation in its polarization state. We show that from these gratings it is possible to generate periodic phase wave fields.

The interference fringes formed by interferometers based on the use of uniaxial wedges are found. The special case of the Babinet compensator is studied and the analytical results are compared to the experimental ones.

The aim of this work is to show how to determine the refractive indices and the direction of the optical axis in uniaxial prisms. The method is based on: the measurement of minimum deviation angles, to apply the symmetry between incident and emergent rays in that condition and the measurement of the inclination of the extraordinary spectral lines in respect to the ordinary ones.

The sensitivity of the attenuated total reflection (ATR) technique to surface modifications allows the study of biological or medical phenomena where solutions segregate to form a layer on the walls of the sample holder. We present an immunoassay study of IgG antigen reacting with specific antibodies in saline solution on an aluminum thin-film attached to a prism, forming the bottom of the container where the reaction takes place. During the reaction a layer is adsorbed on the aluminum film showing a resonant absorption peak in the reflected signal that shifts towards larger angles of incidence at every step of the reaction. These shifts are related to the optical properties and the thickness of the adsorbed layers and may be quantified. This work presents the experimental setup and qualitative results of this reaction.

A high sensitivity laser polarimeter LP101M employing a He-Ne laser has been designed and constructed as a detector for liquid chromatography achieving a sensitivity better than 0.001 degree. The operation principle and technical characteristics of this instrument are described. A liquid gel chromatography column system suitable for sugar cane juice analysis was also designed and calibrated. It separated and analyzed the medium molecular weight carbohydrates and demonstrated the strong influence of these substances in the conventional polarimetric determinations.

An algorithm for enhancing different regions of interest in bone radiographs using mathematical morphology is presented. The calculation of the local histogram equalization (LHE) of a gray scale image throws into relief different textures in the image. These textures are segmented using morphological operations which include morphological gradient and opening by reconstruction. All the operations can be implemented optically so the computational time decreases very fast with respect to digital processing. Digital results are shown and optical implementation is discussed.

By means of capturing the image of a fruit, in this case a mango; the lenticels are used as one of the criteria in determining levels of biological development in this variety of tropical fruit. It has been reported that when the fruit reaches a level of ripeness in its biological development, the lenticels (small marks) separate and disappear in such a way that the superficial density of lenticels changes continually during this process; so that when the level of biological development increases the superficial density of lenticels diminishes. This paper presents an image processing method based on a procedure that automates the process of capture, increase, improvement, definition of surface and also counts the lenticels of the image of the mango by means of binarization.

A generalization of Hamilton's formalism for geometrical optics is given here to provide more convenient descriptions of the optical properties of certain classes of systems. This generalization is made by replacing the usual points and planes that are used as references in the definition of characteristic functions by more general surfaces. In this context, the fractional Legendre transform is used in the semigeometrical estimation of field propagators to eliminate errors introduced by caustics.

A method for the calculation of the axial illuminance and chromaticity as polychromatic merit functions of optical imaging systems is presented. We show that the Wigner distribution function of the pupil of the system allows us to obtain all the monochromatic components needed for the calculation of these parameters. From this single phase-space representation, the merit functions can be obtained in a polar fashion for a variable spherical and longitudinal chromatic aberrations. Numerical examples for an axially apodizing filter are shown.

Based on an all-optical system, a chart of a fractional Fourier transform with many fractional orders is proposed. Using the digital image processing terminology, this chart is known as the Radon-Wigner transform. It enables new aspects for signal analysis which are related to time- frequency and spatial frequency analysis. The given approach for producing this chart starts with a one dimensional input signal while the output signal contains two dimensions. The optical setup for obtaining the fractional Fourier transform was adapted to include only fixed free space propagation distances and variable lenses. With a set of two multifacet composite holograms, the Radon-Wigner chart has been experimentally demonstrated.

We relate the definition of the continuous order derivative of a function, f(x) with Fourier transform F(v), with the continuous order derivative of monomials and polynomials, in x, as well as with that of functions expressible as Mclaurin series.

The use of anamorphic optics allows us to obtain a fractional Fourier transform with a different order in two orthogonal axis. This possibility is checked with a laboratory experiment, where an anamorphic FRT is optically obtained, with a good agreement with the computer simulated result. Several applications, such as correlation and multiplexing, can take advantage of the new degree of freedom added by this method.

A wavelet transformation based optical processor for performing invariant pattern recognition is suggested. It contains a composite filter that consists of several wavelet daughter functions derived from the reference object. The intensity of the correlation peak is determined to be invariant to various deformations of the reference object. Computer simulations show explicitly the promising ability of the new technique.

Scattering from 2-dimensional randomly rough surfaces is considered using a simple ray trace. The effects of phase and polarization are taken into account. It is shown that the patterns observed experimentally are due to the interference of the double scattered rays which gives a pattern with four-fold symmetry.

Algorithms for reconstruction of surface profiles from scattering data are presented. The methods are based on surface profiling methods of confocal microscopy. They use the principle of the three-dimensional spatial frequency content, and the Kirchhoff approximation.

We have studied the diffusion curve evolution in variable translucent rough surfaces. In order to carry on these studies, we used cells having an internal diffuser face. Inside these cells, we place a liquid of controllable refraction index. In this way, we are able to obtain a great range of roughness values without changing the correlation length. In this paper we extend the results obtained in another work presented in the II Iberoamerican Optical Meeting. We verify the existence of a similar phenomenon and its relation with the surface roughness. Moreover, we must note that this work has been done with coherent, but we think that we deal with a predominantly geometric phenomenon, not quite in agreement with most of the authors that are studying this subject.

It is widely known that both the speckle pattern generated by the axial movement of a rigid diffuser surface, as well as the speckle pattern registered with low resolution, present blur-up. In the first case a blur-up criterion was proposed and applied to the study of vibrations. The statistical and optical properties of dynamic diffusers are also well modeled and well known. This paper proposes a numerical criterion to determine the blur-up of the speckle pattern resulting from superposition patterns generated by dynamic diffusers. Its application is illustrated in the analysis of the Brownian motion of colloidal particles.

Various optical techniques have been developed over the last few years for real-time analysis of surfaces and near-surface regions of semiconductor epitaxy. These techniques are providing insights into microscopic mechanisms of epitaxy and opportunities for sample-driven closed- loop feedback control of the epitaxial growth process. Both aspects are expected to become increasingly important as device complexity increases and tolerances become more stringent. Examples are provided and opportunities discussed.

Analytical results of the stimulated Raman self-scattering influence on the propagation of femtosecond optical solitons are presented. The spectral perturbation method is developed, and we show that this method allows us to obtain a quantitative estimation of the frequency shift for an arbitrary relation between the parameters of the soliton pulse and the Raman line.

The boundary perturbation method is applied to investigate the changes in the lowest modes of optical fibers sustaining super-Gaussian beams due to the cladding with a constant refractive index. This contribution illustrates the exploitation of quantum-mechanical analogies and methods in the study of optical phenomena.

A sensing scheme for multimode fiber-optic interferometer using a photorefractive double phase conjugator is proposed. The conjugator acts as a converter of light amplitude distribution of the fiber modes into the same wavefronts propagating in the same direction. The scheme has high light efficiency and allows interferometric detection of high speed intermodal phase fluctuations and it is self adaptive for environmental changes. The results of experiments for vibration detection are presented to demonstrate the feasibility of the proposed scheme. In our experiments, a double phase conjugator based on photorefractive waveguide- like BTO crystal was used.

We have developed several light modulation techniques, using all-fiber interferometers, based on the combination of the dynamic phase response and the control of the polarization. On the one hand, two all-fiber Mach-Zender interferometers have been designed to generate rf modulated light at 633 nm and 830 nm. The actual experimental arrangement covers the frequency range 1 kHz to 1 GHz and has been proposed as a frequency response calibrator of optical detectors. On the other hand, a technique to modulate the transmission of all-fiber mirrors (Sagnac interferometers) has been developed. We have demonstrated the use of this technique to modulate the transmission in the frequency range 1 - 10 MHz and to generate 200 ns pulses.

We report the observation of self-pulsing behavior in a linear cavity Er-doped fiber laser pumped by a 980 nm laser diode. Stable self-pulsing is observed for both continuous-wave and low frequency chopped pumping. By measuring the time evolution of the transmitted pump light, we were able to observe a long build-up time (around 5 ms) for lasing action to take place. While the self-pulsing behavior of similar lasers has been recently reported, the long laser build up times have not been reported before. A numerical model for the time and space dependance of the excited state populations of the Er-ions reproduces some of the observed features.

The usual phase-stepping algorithms are employed to evaluate the phase of Fizeau interferograms in topographic measurements. The superposition of the interferogram with a Ronchi grid provides a Moire pattern. The phase modulation is obtained by the in plane displacement of the grid, while a sinusoidal intensity pattern is obtained by defocusing the image acquisition system. In this work, the measurement range of the method in the function of the maximum variation of height surfaces is calculated and verified.

Experimental mechanics for finding out stress fields of a metallic structure are quite difficult if the structure surface shape is unknown. For alleviating it, numerical techniques such as finite element methods (FEM), have been employed. Three-dimensional structure modeling is required before using FEM. However, for complicated structure shapes the 3D modeling is time consuming. Then, analyzing real engineering structures with FEM requires their geometrical coordinates that can be linked to FEM through a commercial CAD package. In this paper optical and mechanical methods for digitizing 3-D structures are described. The systems can be automatically linked to a CAD system which sends the 3D files to a FEM software for stress analysis.

In this paper, a new and useful technique is presented to recover the object surface shape that contains discontinuities and additionally a wrinkled texture. In conventional photometric and fringe projection methods it is difficult to recover discontinuities and wrinkled texture, simultaneously. For carrying out the proposed technique, it is necessary to have the projection of a cosenuidal ruling with low and high frequencies. The technique recovers the discontinuities by filtering out low frequency in the Fourier spectrum. On the other hand, the wrinkled texture is detected by using the high frequency of the ruling spectrum. Finally, we use a joining algorithm to get the global object shape.

A Fizeau interferometer has been built to test aspherical and concave telescope mirrors. Results of one method used to evaluate the maximum number of fringes when the interferogram image is projected on a CCD device are mentioned. Some complementary techniques have been utilized to analyze interferograms using this kind of interferometer. A deterministic approach to the regularization term added by Marroquin and Rivera (1995) to the least-squares unwrapping technique is shown.

The construction of a phase shifting interferometer is described. The movable reference mirror is driven by a piezoelectric transducer. This piezoelectric was completely characterized in order to know the range for linear behavior. Besides this, a special voltage source was constructed to feed the piezoelectric through software. Several dephase interferograms were digitized in a PC computer.

Spectrally resolved white light interferometry (SRWLI) is applied to 1-D profilometry. The technique allows us to deal with discontinuous profiles without any ambiguity. Experimental results show good agreement with phase shifting profilometry; nanometric resolution is attained. In order to extend the method to 2-D samples, double spectral modulation (DSM) is applied using a new experimental set-up which enhances luminosity.

A scanning laser time-delay interferometric detector (TDID) can serve as an excellent optical computer for simple, rapid, high-resolution image reconstruction in a novel multiple- frequency, multiple-transducer acoustic microscope. The new microscope will employ three insonifying transducers to obtain holographic projections from three different directions and using three different frequencies in reconstructing tomograms of microscopic objects. To do this the detection system should detect with equal sensitivity in all directions of propagation of the traveling ultrasonic waves that emerge from the object with the image information. The TDID is capable of accomplishing this task and at the same time providing high resolution, high detected signal strength and a quadrature output for producing the necessary holographic projections.

The bulk electric-dipole contribution to the optical second harmonic generation (SHG) of centrosymmetric systems is (almost) null, so that SHG constitutes a good optical probe of their surface. We present a generalized hydrodynamic model for the calculation of the SHG spectra of simple metals with a smoothly varying surface electronic density profile. The equations of motion include a pressure term derived from the Thomas-Fermi-Dirac-von Weizsacker energy-functional, thus it includes some effects of exchange and correlation. The surface is capable of sustaining multipolar collective modes besides the ordinary surface plasmon. The former have proved capable of sustaining multipolar collective modes besides the ordinary surface plasmon. The former have proved to be very elusive and have only recently been observed with HREELS. We have obtained very large peaks in the non-linear susceptibility at the frequency of the multipolar resonance and its subharmonic, at which the SHG efficiency is enhanced several orders of magnitude, suggesting the usefulness of SHG as a probe of surface collective modes.

A study of the diffraction of a light wave at a periodic vacuum-metal interface is presented here for waves that carry enough energy to excite a nonlinear response in the metal. We analyze the generation and diffraction of the second-harmonic of the pump frequency. An approximate boundary condition of the 'surface impedance' type that simplifies diffraction problem is introduced. The results are shown to be in good agreement with the ones obtained by using the boundary conditions derived from the hydrodynamic model.

Polarized Raman spectra of L-asparagine were measured as a function of temperature. Various qualitative changes were observed. We believe that these changes are produced by hydrogen bond alterations and a second order phase transition around 160 K. We also observed anharmonicity in bands linked to the hydrogens bonds.

We report the study of the third-order optical nonlinearities of amorphous selenium, using picosecond pulses at 1.064 micrometer, from a mode-locked Nd:YAG laser. The Z-scan technique was used to resolve the absorptive and refractive contributions to the nonlinear response of the material, including their sign. The chosen wavelength lies to the lower photon energy side from the absorption edge for the material studied, the interaction is therefore nonresonant and electronic in origin. We measured an n₂ equals -0.06 cm²GW^-1, with negligible two-photon absorption. We discuss the influence of two photon absorption on the nonlinearity observed.

Selection of electromagnetic modes in a 1-dimensional dielectric periodic structure with a defect in the central period, is used to obtain sharp resonances in the generation of second harmonic light. We have observed experimentally the enhancement of the nonlinear interaction in the vicinity of the defect when the second harmonic wave is excited for modes within the forbidden zone or stop band. We have also observed an enhancement near the band edge, where the group velocity approaches zero. These results are in agreement with an analysis that includes the interference effects arising from multiple reflections in the periodic structure.

A method for the measurement of the nonlinear refraction and absorption in optical materials studying the distortions of the wavefront of light beams is proposed. Using a one-shot CCD camera, the beam profile changes are recorded for different cell positions. Usual Z-scan, eclipse Z-scan and the total profile distortion signals can be extracted from these data. Proportionality between the measured total signal and the induced phase shift is demonstrated. A comparison between this signal and the usual Z-scan signal is performed.

Nonlinear parametric effects such as the suppression of period doubling, the shift of the bifurcation point, a scaling law relating the shift and the perturbation amplitude, an influence of the detuning on the suppression, reaching of the maximum gain between original and shifted bifurcation points, and a scaling law for idler power are experimentally observed near period doubling bifurcation in a loss-driven carbon dioxide laser which is subjected to periodic loss perturbations at a subharmonic frequency.

The frequency-modulation continuous wave (FMCW) interferometry is used in combination with a reference technique by measuring the linear thermal expansion coefficients in metallic bars. Unlike other methods, the technique shown provides results in real time with a very good accuracy, and fulfills the requirements of absolute distance and displacement measurement. First results yield uncertainties of about 50 microns over a 0.1 - 10 cm dynamic range.

Another way to explain the autoimaging effect is to consider it as the Fresnel diffraction field obtained with the Huygens-Fresnel model using Young spherical waves generated by each transparent point in the ruling. This model has been used by Latimer and Crouse (1993) and later commented by Szwaykowski (1993). Here we present another analysis more detailed and rigorous than these, using the same Huygens-Fresnel model.

An optical arrangement for liquid-level measuring is proposed. The method is based on self- imaging or Talbot effect. Knowing the container dimensions of a liquid, it is possible to obtain the volume changes by the liquid variation in the container. The optical arrangement consists in detecting a diffraction field of a Ronchi grating illuminated by a collimated beam. This field is first reflected by the interface liquid-air, afterwards casting on a second Ronchi grating. This superposition produces a Moire pattern when the Talbot plane of the first grating coincides with the second one. If the travelled path of the wavefront is not a Talbot distance, the Moire pattern is lost. In this way, it is necessary to move the second grating up to see the sharper Moire fringes. The grating change gives directly the level change. Description of the experimental setup and results are shown. Strengths and weaknesses of the method are presented. The future lines of work are given in order to have an automatic and compact instrument.

The aim of this paper is to implement the self-imaging phenomenon by utilizing an incoherent to coherent conversion in a non-holographic approach. This is materialized by using a photorefractive BSO crystal to encode as modulation of birefringence an incoherently projected Ronchi grating that will be coherently read out by collimated laser light which is outside of the spectral sensitivity range of the crystal. The transmitted output through the analyzer is written in terms of: a component of the linear polarized part of the readout wavefront exiting the crystal, and a component of the elliptically polarized part of it. In this way, the incoherent input is converted in a coherent output that repeats itself under free propagation. By rotating the analyzer the contrast of the replicated grating is controlled. Experimental results are presented and possible applications are discussed.

We provide a supersymmetric analysis of the Maxwell fisheye (MF) wave problem at zero energy. Working in the so-called R_o equals 0 sector, we obtain the corresponding superpartner (fermionic) MF effective potential within Witten's one-dimensional (radial) supersymmetric procedure.

This work is intended to motivate the use of telecentric systems in machine vision. For this, some characteristics of this kind of system and the design methodology are shown. Also, we present a simple telecentric lens designed to be used with a half-inch format CCD.

The IDS summation model was used to explain the perception of defocused symbols. Twelve different computer-generated words were used as stimulus for sharpness evaluation by a group of observers and the result compared with the model response, obtained by software implementation. The symbol luminance slope was used as a parameter. The correlation coefficient is greater than 0.99.

When optical systems are designed, the final stage corresponds to the optimization of an initial design, and frequently the methods of damped least squares are used. However, some methods, such as the one mentioned, find local minimums and not the global one. Therefore, the solution depends mainly on the initial design. The method proposed in this work, is based in the genetic algorithms that find the global minimum, and besides an initial design is not necessary to begin the optimization process.

The ALSIE (Automatic Lens Design By Solving Inequalities, T. Suzuki, et al., J. Opt. Soc. Am., 56, 677, 1966) algorithm is a powerful lens design procedure for the optimization of conventional and unconventional lens systems. However, a problem of the ALSIE algorithm is the selection of an adequate set of boundaries to the performance functions. In this work a procedure of selecting the boundaries is discussed. It is experimentally found, by designing a doublet lens to be used in a multiple imaging lens system, that the selected boundaries dealt to a faster convergence than with the original selection of boundaries.

Recent experiments on optical bistability in amorphous Se an Ge_xSe_1-x chalcogenide thin films are presented. The results show a strong dependence on the energy density and on the sample composition. The faster responses are for pure selenium as the content of germanium is increased the material response is slower. A simple model is proposed in order to explain the observed results.

We present a matrix formalism for describing the near field diffraction patterns, at fractions of a Talbot distance, of a grating whose unit cell is composed with a discrete substructure.

We discuss the formation of self-images in an optical fiber with quadratic refractive index variations, and in its lens tandem equivalent setup. We identify two family sets of self-images. The first family set has geometrical magnification less or greater than unity. The other family set is obtained by longitudinal replication, with unit magnification of the first family set.

A telescope was needed that would fit into the cramped quarters of an earth orbiting satellite and also be light in weight. The first requirement dictated that the system had to be folded; the second made undesirable any system of planar folding mirrors. My solution was to use a pair of confocal conic mirrors but with their axes subtending a predetermined angle. This made it possible to arrange the mirrors, more or less, to fit the available space. I've called this kind of system a Schiefspiegler after a book describing similar telescope designs. At this point the system consists of a pair of confocal conic mirrors, prolate spheroids to be precise, whose axes subtend an angle (beta) and that intersect at the common focus. The other parameters are the two eccentricities, (epsilon) ₁ and (epsilon) ₂, the two vertex radii of curvature r₁ and r₂.

Reflective block optical systems have been used to achieve tasks realized by lens systems, but offering compactness and flexibility to construct optical computing systems. Thus, the reflective optical systems have to achieve optimal optical performance. In this work, we use the procedure of ALSIE (Automatic Lens Design By Solving Inequalities, T. Suzuki, et al., J. Opt. Soc. Am., 56, 677, 1966) to optimize reflective optical systems. To realize the optimization some specific considerations are discussed. The spherical aberration of a reflective optical system is optimized by the present method, showing the optimal optical performance.

An analysis of the light focusing and collimation properties through an inhomogeneous planar optical waveguide whose refractive index profile is given by a hyperbolic secant function is presented from a geometrical point of view. Likewise, a light collimator for a point source and a light deflector for tilted plane illumination are designed.

We describe an optical technique for setting a lensless correlation between two binary, pseudorandomly encoded gratings, under noncoherent illumination. We show that this result can be applied for implementing a novel Lau sensor. Experimental results are reported.

In this work we present a numerical and iterative algorithm for the reconstruction of degraded space variant imaging. The method works using the function: R_G(u,u') equals G(u+u'/2)G(u-u'/2), which is the output of a bilinear system, G(u) is the Fourier transform of the degraded image function, g(x). Then using an iterative technique based on the damped minimum mean squares estimation method the estimated object is obtained when a Wiener filter, in the bilinear system, is applied to the R_G(u,u') function.

The Buchdahl-Rimmer aberration coefficients are commonly used in optical design programs for the evaluation of third- and fifth-order aberrations. The information given by these coefficients is difficult to interpret since there is no direct relationship between the numerical value of the coefficient and its effect on the image quality, i.e. the most important aberration is not necessarily the one with the largest numerical value. To look at the effect that each aberration has on the image quality it is necessary to re-normalize the Buchdahl-Rimmer coefficients. The purpose of this work is to re-normalize the Buchdahl-Rimmer coefficients of the wave aberration function in terms of the strehl intensity ratio as well as to re-normalize the Buchdahl-Rimmer coefficients of the geometric aberration function in terms of the RMS spot size.

Analytical expression for the possible oscillation frequencies generated by a single-mode linear-cavity fiber laser are presented. The mathematical model takes into account dispersion and nonlinear self-phase modulation.

A nonlinear spectrally selective Sagnac interferometer based on a special configuration of a birefringent fiber is demonstrated. Spectral resolution less than 1 nm can be easily obtained. The theoretical and experimental characteristics of the mirror are derived. The applications of this fiber reflector as a multichroic mirror and passive mode-locking and Q-switching element are discussed.

We have worked out the guided mode spectrum of several cylindrical multilayer structures as dielectric/metal/dielectric, dielectric/dielectric and dielectric/dielectric/metal/dielectric. The third structure can be regarded as the combination of the first and second, and its mode spectrum as the coupling between the modes of the other two. The properties of the mode spectrum of the final structure can be used to design wavelength filters and sensor applications.

We have carried out a series of numerical experiments on the dynamic behavior of optically pumped J equals 0 yields J equals 1 yields J equals 0 lasers operating with isotropic ring cavities and linearly polarized pump fields in the following conditions: (1) fixed linear polarization of the pump beam and applied axial magnetic field; (2) sinusoidal modulation of the pump polarization direction. Among rich dynamics, we report the first observation of polarization chaos in the laser output in both cases. In case (1) the laser polarization is linear but its orientation changes chaotically; in case (2) chaotic evolution of the ellipticity is also found.

HeCd⁺ lasers based on hollow-cathode designs may be operated under conditions in which multi-line emission (white-light laser) can be realized. It has been shown that all laser lines attributed to transitions in Cd II are accompanied by contributions from the complex He(DOT)(DOT)Cd⁺ which also exhibit some gain. A diode laser probe has been used to investigate the line profiles of some of the laser transitions, and to explore the role of energy transfer in helium-cadmium collisions.

A new femtosecond optical technique, similar to the classical stroboscopy, for the study of ultrafast oscillating systems is presented. We apply this method to detect resonances of liposomes (artificial biomembrane) stained with potential sensitive dyes. The spectral behavior of a selection of potential-sensitive dyes inside the membrane is also studied.

The voltage and current behavior of a charge transfer (C-to-C) N₂ laser was analyzed using the program IS-SPICE. The electric power across the laser head was analyzed as a function of the parameters of the circuit. The results can be used to establish general criteria for optimal laser design based on this circuit.

The photophysical properties (photostability, spectral-luminescent and generation properties) of eight new organic compounds have been studied, in which the molecular composition of two flurophores -- 1,3,5-triphenylpyrazoline and 2,5-diphenylzoxazole-1,3 (or 2,5- diphenyloxazole-1,3,4) -- were included. The effect of the structure of the investigated molecules and the polar properties of solvents on the spectral position of absorption and fluorescence bands was analyzed. The dyes have been found to have a fluorescence quantum efficiency (gamma) between 0.40 and 0.82 in these solvents. The dye laser performance using these dyes has also been investigated using the same solvents under nitrogen-laser pumping to compare them with the commercially available standard dye POPOP, which generates radiation in the violet spectrum region and allows the extension of the range of the active media used in liquid lasers in this spectrum region. A tuning range of nearly 60 nm was obtained in the blue region with efficiency up to 85% in comparison to the standard dye POPOP.

In this paper the spectral-luminescent characteristics and study of laser generation properties of new organic compounds are shown, whose particularity consists of forming excited state complexes that allow laser effect obtention. The intense generation of radiation observed in these excited state complexes allows laser creation by active media working at a broad multi- spectral range (the violet and yellow region of the spectrum). The dye laser performance using these dyes has also been investigated using the solvents ethanol and toluene under nitrogen- laser pumping to compare with the commercially available standard dye POPOP, which generates radiation in the violet spectrum region.

The model of photoinduced growth of X⁽²) susceptibility in glasses is considered. The process of formation of X⁽²) grating includes the formation of charge transfer states under interference of multiphoton absorption processes without throwing electron in conduction band. The results of calculation of photoinduced second harmonic generation (PSHG) efficiency on this grating are compared with experimentally observed PSHG in barium-boron-silicate glasses doped of rare-earth ions.

We present a theoretical and experimental analysis of the Z-scan technique in thick media with thermal nonlinearity in steady-state regime. The theoretical model considers the thick medium as a stack of thin thermal lenses. Numerical solution for the Z-scan technique is obtained. Experimental results for the technique using a sample of methylene blue in a solvent under cw illumination from a 10 mW He-Ne laser beam are obtained. Comparison of the experimental and theoretical results is made. Good agreement between theory and experiment is obtained.

The present paper is the second part of a study of the laser metal surface hardening techniques using a 3 kW cw carbon dioxide laser. The laser alloying and laser cladding techniques are analyzed by experiment. The main results of both processes are given as a function of the more important parameters involved in them: the laser specific power, energy density, volumetric energy density, etc. Finally, the results of a wear resistance mechanical assay are included in order to compare the different surfaces obtained by all the used laser techniques, including in this paper and in the previous one.

In this work we analyze a feasibility to use non-resonant polarization mode coupling in birefringent fiber for simultaneous strain and temperature quasi-distributed measuring. The method employs white light and a two-mode fiber containing in-fiber sensing interferometers. This technique allows us to interrogate local sensors and demultiplex output signals using a compact grating spectrometer. First experimental results are presented.

A simple identification method of theodolite axes is presented. By directing a laser beam along the theodolite optical axis a diffraction figure of the cross hairs is generated. An analysis of the figure reveals the main and secondary axes. Interferential alignment is also used for precise identification of the optical axis. This method is easily applied by visual inspection. It is simpler than conventional methods used in surveying.

Yttrium-aluminum garnets (YAG) doped with a rare-earth element, including terbium (Tb), thulium (Tm), and Erbium (Er) produce the phosphorescence. YAGs may be synthesized by baking hydroxides of their constituents at a high temperature. No flux is required and the temperature of the solid state synthesis may be decreased to only 1150 degrees Celsius when the hydroxides are coprecipitated. We report here on the results of the thermoanalytical studies of the coprecipitated hydroxides in the YAG solid state synthesis.

A simple method for centering a Gaussian laser beam is proposed. It consists of partially blocking out the beam by an opaque wire; when the power of the transmitted beam is brought to a minimum, by moving the relative position of the beam and the wire, the center of the beam and that of the wire are in coincidence. By using the usual formulae for Gaussian beams, the behavior of the power variations with the relative wire-beam position, as a function of the width of the wire are analyzed. The error of the method is also analyzed and it is shown that the optimum case is when the wire diameter equals (root)2 the beam radius. We show some experimental results.

A new sensor is proposed combining arrays of interference filters with resonant cavities of high interference order (Fabry-Perot resonators) using both, high capabilities of accurate thickness control in silicon substrates derived from microelectronics and thin-film optics techniques. The interest of this type of device would be the fabrication of high resolution multigas sensors, compact, with no moving parts, for accurate measurement of low concentration gases.

The electronic structure of (211) AlAs/GaAs superlattices at the (Gamma) point of the superlattice is studied for (2,2) less than or equal to (n,m) less than or equal to (20,20), where n(m) is the number of principal layers of AlAs (GaAs). The calculations are based on a sp³s^* empirical tight-binding model and on a surface green-function matching analysis. The evolution of the energy gap versus the variation of n and m, and the confinement of the different states are discussed. Also, the orbital character of the wave functions is studied.

Optical bistable response of a molecular aggregate modeled as a linear chain of two-level molecules is shown. We have found that bistability may exist but bistable response is strongly affected by spatial inhomogeneity of the aggregate population.

Optical anisotropy in the refractive index and in the absorption coefficient of GaTe has been studied in the layer plane. The refractive index has been determined in the wavelength range from 0.7 to 25 micrometer and the absorption coefficient in the range of energies from 1.6 to 2 eV. The refractive index dispersion is interpreted through Phillips-Van Vechten and Lorent- Drude models, yielding values of the Penn gap of E_pg (perpendicular b) equals 3.37 eV and E_pg (parallel b) equals 3.58 eV. The absorption coefficient has been found to be very slightly anisotropic, which is shown to be coherent with the Se pz-like character of the valence band.

This paper demonstrates a newly experimental solution to obtain flat free surfaces of confined liquids in small containers and a useful approach to build-up an optical level of very small dimensions.

The readout visibility of a slit image encoded as a variation of birefringence in a BSO crystal is theoretically and experimentally analyzed. The photorefractive crystal is employed as an optical converter by encoding the incoherent input as modulation of birefringence and then reading it out with linear polarized light. When an analyzer is located in the output, the system behaves like a dynamic intensity filter. The output visibility is presented in terms of the input visibility and for different slit widths. It is established that the output visibility can be strongly or weakly dependent on the input visibility according to how the pass-plane of the analyzer is set.

In this paper, numerical and experimental methods for vibration mode analysis are reported. Some of the vibration modes of an aluminum plate were investigated by modeling with the finite element method (FEM). An out-of-plane electronic speckle pattern interferometer (ESPI) was the experimental method used to analyze the same vibration modes. Experimental and numerical methods are compared. These results were obtained as part of a project to identify the requirements for correlation between experimental modal measurement data and finite element numerical modal estimation.

We analyze the effects of systematic coating thickness errors on the performance of an optical component. The coating thickness error results in a phase shift that differs from the design values for both the s- and p-polarized light and changes the apparent surface figure of the optical component.

Focalized patterns generated at fractional Talbot distances of periodic phase gratings are discussed employing the Fresnel diffraction approach. Conventional and non-conventional focalizing cells are distinguished. The phase reliefs that generate patterns with maximum compression ratio, at a given distance, are described. Emphasis is done in the cases for which the 'resolution limit' of the focalized pattern is smaller than the normally expected one.

A polychromatic object recognition based on a circular decomposition preprocessing of RGB components and a multichannel matched filtering is described. Computer simulation results are provided to recognize a color target among objects of similar shape but with different color contents.

In this work we apply a pyramidal Gabor image decomposition to pattern recognition. The recognition process is based on a multichannel correlation. The filter is adapted in each channel to the corresponding decomposition of the object to be recognized. The results obtained with the multichannel process are compared with those obtained by using the classical matched filter (CMF) and phase only filter (POF).

Simple, recursive ray-trace equations are presented that describe exactly a ray propagating through a series of coupled, confocal, prolate spheroids. Vector formulation is employed for characterizing the ray propagation in different planes through the spheroid axis of symmetry.

There is continued interest in calculation of the electromagnetic field distribution in the focal region of an optical system of high numerical aperture. Important applications include microscopy and optical information storage. Unfortunately direct evaluation of the diffraction integrals is extremely time-consuming. We have developed a new method in which the illumination is expanded in a series of multipole terms, each of which gives rise to a focal field which is an analytic function in three-dimensional space. The electric energy density in the focal region has been calculated for various lens and mirror systems.

A technique is presented for improving 3-D resolution in confocal scanning microscopy. The technique is based on the equal contribution to the image of the illuminating and the collecting lenses. It is proposed, then, to apodize such lenses with complementary filters. The combined action of both filters produces a narrowness of the point spread function of the system both in the image plane, and along the optical axis.

We describe a technique for aligning the axis of an optical system to the axis of a rotating mechanical system. The optical system is focused onto a linear grating that rotates in conjunction with the mechanical system. Light reflected from the grating produces an interference pattern in the pupil of the optical system. Temporal modulation of the fringes in the interference pattern is observed as the mechanical system rotates of the optical and mechanical axes are misaligned. Our application for this technique is in aligning an optical and mechanical system for writing circularly symmetric computer generated holograms. Experimentally we demonstrate alignments to accuracies of 0.1 micrometers.

Human activities are altering the earth system at the local, regional, and global scales. It is therefore of the utmost importance to track the workings of mother earth in order to detect any changes at their early stages so that appropriate actions are taken to understand, assess, control or prevent the adverse effects. A number of deleterious effects to the environment can, at least in part, be ascribed to air pollution, namely, the thinning of the ozone layer, the related increase in the occurrence of skin cancer, the warming of the earth system, photochemical smog, acid rain/fog, acidification of soils and waters, forest decline, etc. It is therefore necessary to monitor the most relevant processes of the earth's atmosphere, namely, the energy input, the dynamics and the chemistry. In this contribution I mainly focus on the latter, specifically, on the measurement/monitoring of atmospheric compounds. To understand atmospheric chemistry and air pollution it is necessary to have reliable and accurate values of the mixing ratios of the numerous atmospheric gases and of their diurnal/seasonal variations and long-term trends. In this contribution I present an overview of the most relevant optical remote sensing techniques that are rapidly becoming the methods of choice to probe the chemical composition and physical state of the atmosphere, especially when high selectivity, sensitivity and fast-time response are required.

In the present work are given the results of the application of laser metal surface hardening techniques using a cw carbon dioxide laser as an energy source on steel 65 G. The laser heat treatment results are presented theoretically and experimentally. Continuous wave carbon dioxide laser of 0.6, 0.3, and 0.4 kW were used. A physical model for the descriptions of the thermophysical laser metal interactions process is given and a numerical algorithm is used to solve this problem by means of the LHT code. The results are compared with the corresponding experimental ones and a very good agreement is observed. The LHT code is able to do predictions of transformation hardening by laser heating. These results will be completed with other ones concerning laser alloying and cladding presented in a second paper.