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This paper describes the development of a laser system for the digitalization and three‐dimensional reconstruction of solid objects. The first step consists of applying on the object a linear sweeping of a thin laser line using a laser diode with 635 nm and 5 mW, a motorized stage for linear displacement of 138 mm, and a controller with RS232 interface. The next step consists of capturing and transmitting the image of the deformed line on the object to a computer. For this step was used a monochrome camera CCD, and an image acquisition board. The last step consists of the three‐dimensional reconstruction of the solid object. All the corresponding algorithms were implemented using the programming language LabVIEW.

In this work we introduce deformed creation and annihilation operators which differ from the usual harmonic oscillator operators a, a† by a number operator function  = âf(n), † = f(n)â†. We construct the deformed coordinate and momentum in terms of the deformed operators and maintain only up to first order terms in the deformed operators. By application of the deformed annihilation operator upon the vacuum state we get the ground state wavefunction in the configuration space and the wavefunctions for excited states are obtained by repeated application of the deformed creation operator. Finally, we compare the wavefunctions obtained with the deformed operators with the corresponding Morse eigenfunctions.

It is well known that interferometric techniques used to measure the modal parameters of vibrating objects require the conversion of phase values to out‐of‐plane values. This task is not simple and often only an approximation is available. In this work, an oscillation frequency measurement is proposed using interferometric techniques without applying out‐of‐plane conversion. In this technique a binary pattern is projected on a cantilever surface and a mathematical model based in interferometry of phase extraction is used for obtaining phase differences of two consecutive frames, captured while the cantilever is vibrating in a natural mode. A projected binary pattern on a cantilever surface is considered as an interferometric pattern with a carrier frequency, which is introduced by the grating period. The deformations of the projected grating period are considered as the desired phase in an interferometric pattern. Period deformations contain information about oscillations and therefore, about modal shape ...

In this work, we report thermo‐optical properties of nanofluids. Spherical gold nanoparticles obtained by laser ablation in condensed media were characterized using thermal lens spectroscopy in SDS‐water solution pumping at 532 nm with a 10 ns pulsed laser‐Nd‐YAG system. Nanoparticles obtained by laser ablation were stabilized in the time by surfactants (Sodium Dodecyl‐Sulfate or SDS) in different molar concentrations. The morphology and size of the gold nanoparticles were determined by transmission electron microscopy (TEM). The plasmonic resonance bands in gold nanoparticles are responsible of the light optical absorption of this wavelength. The position of the absorption maximum and width band in the UV‐Visible spectra is given by the morphological characteristics of these systems. The thermo‐optical constant such as thermal diffusion, thermal conductivity and dn/dT are functions of nanoparticles sizes and dielectric constant of the media. The theoretical model existents do not describe completely this relations because is not possible separate the contributions due to nanoparticles size, factor form and dielectric constant. The thermal lens signal obtained is also dependent of nanoparticles sizes. This methodology can be used in order to evaluate nanofluids and characterizing nanoparticles in different media. These results are expected to have an impact in bioimaging, biosensors and other technological applications such as cooler system.

The frequency wavelet analysis is demonstrated using Coiflets scaling signals and wavelets, and an experimental two‐wave mixing arrangement using a photorefractive BSO crystal. In our work we used the Coif12 wavelets to demonstrate the optical implementation of the frequency wavelet analysis. The enhancement of the local features of images is experimentally demonstrated in this scheme. The frequency content of the averaged image consists of low frequency values selected by a low‐pass filtering of the original image. Similarly, the frequency content of the detail images consists of frequency values selected by a high or band‐pass filtering of the original image. A brief exposition about the fundamental concepts of the frequency description of the wavelet analysis is presented, a physical model for the photorefractive wavelet processor is illustrated, and the experimental implementation is performed.

In this paper, we implement a practical digital security system that combines digital correlation, wavelet compression with preprocessing digital images; we applied these biometric system for fingerprint verification or autentication, that it has as pattern unique of recognition the Fingerprint. The system has a biometric sensor, it is charge to capture the images and to digitize them. These images are preprocessing using wavelet‐based image compression and are skeleting for to stand out elements of the image that are considered of greater importance, eliminating the undesired signals, that because of the method of acquisition, or the conditions under which it was captured they appear in the same one. This images are stored in the data base, which to the being passed through diferent algorithms makes a compound filter, that serves as reference or pattern fingerprint for making the comparisons. These comparisons are showing in a graph where are observed amplitude diferent for each one from fingerprint, this make with help Fourier transformed and the correlation operations, that allows to quantify the degree of similarity between two images. Depending on the results thrown by the system at the time of comparing a new fingerprint with the compound filter the access will be allowed or not the user.

Recently, classical optics based systems to emulate quantum information processing have been proposed. The analogy is based on the possibility of encoding a quantum state of a system with a 2N‐dimensional Hilbert space as an image in the input of an optical system. The probability amplitude of each state of a certain basis is associated with the complex amplitude of the electromagnetic field in a given slice of the laser wavefront. Temporal evolution is represented as the change of the complex amplitude of the field when the wavefront pass through a certain optical arrangement. Different modules that represent universal gates for quantum computation have been implemented. For instance, unitary operations acting on the qbits space (or U(2) gates) are represented by means of two phase plates, two spherical lenses and a phase grating in a typical image processing set up. In this work, we present CNOT gates which are emulated by means of a cube prism that splits a pair of adjacent rays incoming from the input...

Light intensity effects on recording photorefractive gratings have been studied in α‐phase proton exchanged LiNbO3 guides. The saturating refractive index change increases as a function of the recording intensity and reaches an unstable region above a certain intensity threshold. The threshold value increases with the exchange time used for preparing the guides, showing a behavior quite similar to that observed with a single beam (non holographic) configuration. Dark decay measurements indicate that dark conductivity can be disregarded with regard to photoconductivity.

Because of the importance of Gaussian beams in optics, particularly in the area of lasers, we devote the present paper to a study of the propagation of these beams. The Gaussian beam, also called a Gaussian spherical wave field, is basically a spherical wave field whose modulus in a plane transverse to the propagation direction varies in a Gaussian fashion. The fractional Fourier transforms (FRFT) were originally introduced in 1980 by Namias as a technique for solving theoretical physical problems. Since then lot of works have been done on its properties, optical implementations and applications; the fractional Fourier transform became an important tool in optics. It is of singular importance in the laser physics the study of the propagation and transformation of Gaussian beams. In this paper the fractional Fourier transform is applied to described the beam waist‐to‐waist transformation of Gaussian beams between input and output reference surfaces; for example, the waist‐to‐waist transformation of a Gauss...

During many years of teaching Physics at the Facultad de Ingenieria‐Universidad de Buenos Aires (FIUBA) and at the Teachers School IES N°1, we have found that students usually have problems in understanding various items of Optics. In this work, we present the difficulties that appear during the teaching and learning processes and some of its causes. We propose a teaching method to make processes easier, to enable a better understanding and a long lasting retention of these topics in the cognitive structure of our students.

The chromatic confocal methods are attractive for various applications, such as imaging of biological samples and semiconductor materials. In this paper a chromatic confocal method to measure the topography, the refractive index and optical thickness of tissues is develop. The experimental model is based on the longitudinal chromatic aberration produced by a diffractive element. The setup is composed by a point polychromatic illumination system, a wavelength‐height codification system of confocal microscopy and a spectral detection system. The illumination system has a broad and continuum spectrum and it is constituted by the combination of a high energy pulsed laser and an air‐silica microstructured optical fibre. The first two systems form a wavelengths segment on the device output. The coding of the topography and the thickness is based in the spectral analysis of the reflected spectral components coming from the surface of the sample and the interphase of the organic membranes respectively. It mean that the most intense spectral components coming from every layer of the sample is identified. The measurement sensitivity is related to the width of the spectral response, which depends on the resolving power of the dispersive element and the detection system. The experimental results and a briefly discussion of the resolution criterion and the perspectives of the work are provided.

In this paper we present the development of a laboratory prototype to obtain the digitalization and three‐dimensional reconstruction of a solid object applying the laser line projection technique. The object under test is placed on a motorized rotary stage, a diode laser system projects a line on the object, the deformed line pattern is acquired by a CCD camera. The information for its reconstruction is extracted of the bi‐dimensional images of the deformation that the laser line suffers according to the three‐dimensional topography of the object. The present prototype digitizes an object in approximately 20 seconds without affecting it the ambient illumination.

In a previous system we showed how the three‐dimensionality of an object can be projected and preserved on a diffractive screen, which is just a simple diffractive holographic lens. A transmission object is illuminated with an extended filament of a white light lamp and no additional element is necessary. The system forms three‐dimensional (3D) images with normal depth (orthoscopic) of the shadow type. The continuous parallax, perfect sharpness and additional characteristics of the image depend on the width and extension of the luminous filament and the properties of the diffractive lens. This new imaging system is shown to inspire an interesting extension to non‐perfect reflective or refractive imaging elements because the sharpness of the image depends only on the width of the source. As new light sources are being developed that may result in very thin linear white light sources, for example, light emitting diodes, it may be useful to further develop this technique. We describe an imaging process in which a rough Fresnel metallic mirror can give a sharp image of an object due to the reduced width of a long filament lamp. We will discuss how the process could be extended to Fresnel lenses or to any aberrating imaging element.

In this paper we present an approach that can be used for transmission of 2‐D spatial information through space‐limited systems such as a single mode fiber (SMF) capable of transmitting only a single spatial pixel. The input 2‐D object is illuminated with temporally incoherent illumination. The axial coherence length is very short and it equals only a few microns. Attached to the input object spatial random phase mask generates different axial shift for every pixel of the input. The temporal delays of the encoding (axial shifts) of every pixel are longer than the coherence length of the illuminating source. Therefore no temporal correlation exists between the various pixels of the input. A lens combines all spatial pixels into one point at its focal plane. The light is coupled into an SMF and is transmitted to a short distance. Although the various spatial pixels were mixed together, since the random mask provided axial delay which was larger than the coherence length of the light source, the orthogonalit...

A description of Fresnel and Fraunhofer diffraction of quasi‐homogenous optical fields in any state of spatial coherence is presented, which clearly differs from the classical formalism. Instead of the propagation of the cross‐spectral density from the diffracting aperture to the observation plane, the diffracting aperture is regarded as a planar quasi‐homogeneous source, whose generalised radiance is carried by the spatial coherence wavelets, and the power distribution at the observation plane is expressed in terms of the generalised radiant intensity. It allows interpreting the negative values of the generalised radiance as “negative energies” emitted along specific directions and subjected to the achievement of the conservation law of energy. This interpretation is not evident in the classical formalism. Consequently, interference can be thought as resulting of energy transfer over a given wavefront, due to the addition of equal amounts of “positive” and “negative” energies, along specific directions, ...

This work presents the characterization of three laser power sources and one pyroelectric radiometer which will be used for a Brazilian radiant power intercomparison. The electrically calibrated pyroelectric radiometer will be used as a reference power meter during the intercomparison and its characterization considering the electrical calibration, the optical absorption film reflectance factor, the linearity and the relative spatial responsivity uniformity is presented. The three lasers sources of wavelengths, 405 nm, 638 nm and 785 nm are characterized according its short term drift. The lasers results showed that 2 lasers sources presented a short term drift of 1% after 1 hour warm up. The all detectors parameters are according to manufacturer specification, instead of linearity and absorption film reflectance factor.

A model that predicts a particle trapping time in an two beams interference laser fields is proposed. This interference consist in a sinusoidal intensity pattern, which is used to translate the particle from the dark fringes to the bright ones. The particle is submerged in a viscous fluid. The model takes into account the irradiance, the wavelength, the fringewidth, the medium viscosity and the size and approximated shape of the particle. From the classical separation of optical trapping force in gradient and scattering force, only the gradient force is considered, expressed in terms of the electric field. Opposing to this force, the drag force is considered in terms of the Stokes force. The expression for the gradient force is the Maxwell equations solution for an homogeneous dielectric dipole in an electric field. For the Stokes force, the RBC is considered an oblate spheroid flowing edgewise. An experimental set up has been designed for the displacement of a single RBC (Red Blood Cell) in blood plasma due to an interference laser field, produced by Argon Ion laser, using several irradiances. To the best knowledge, is the only dynamic model of optical trapping that predicts the particle trapping time and position without experimental results, and is made it in a simple analytical way. This analysis can be extended to other particles of arbitrary shape and trap configurations.

Today, the use of special optical elements for aberrations control is more and more common because these elements reduce the weight and volume of the optical system but the design of these elements is complicated and it is more complicated if we like to use an analytical way; also, in many cases, after an analytic process we must to use an optimization routine with some optical design program. In this work we propose an analytic method to design systems free of spherical and coma aberrations using an aspherical and diffractive surfaces (hybrid element). We analyzed the form of the back principal plane to different shape factor considering the spherical aberration corrected and no corrected. We use the aspherical surface to correct the coma; we obtain this condition curving the back principal plane and centered it on the back focal point. The diffractive element is used to correct the spherical aberration by apply an exact ray trace, and we use the diffractive coefficients as variables. We find these coefficients by solve a first degree equations system. We apply this method to design systems with two surfaces with the object at infinity and with monochromatic light. The last surface is the aspheric surface and also in this surface we put the diffractive element. With our procedure we do not need an optimization procedure.

We report the experimental study of a multicavity fiber laser system conformed by an array of three Erbiumdoped fiber laser cavities. We have demonstrated that through the nonlinear interaction of evanescent fields among one cavity with active modulation and all the others it is possible to accomplish the mode‐locking for all the laser cavities. Moreover, the synchronous pulse generation between cavities is obtained with an appropriate selection of pump intensity, frequency modulation and coupling ratio.

A new optical deflectometric set‐up that combines the linear scanning with sample rotation has been developed [3]. The slopes data acquisition is done in a polar coordinate system. To obtain the profile of the sample from its measured slopes, the integration of the measured slopes in polar coordinates system is necessary. We present two dimensional methods based on the one dimensional integrations in radial and angular directions. We also develop a finite differences method in polar coordinate system. Finally, some numerical results are given to compare the different 2D integration methods presented.

Lippmann interference photography is an elegant process to record colour photographs. From this principle, wavelength multiplexed data storage systems were developed. Hereafter, we propose to further simplify and enhanced the performances of these Lippmann architectures. Therefore, we describe the implementation of an homodyne detection for enhancing the readout signal combined with an architecture in which the access to a single side of the recording medium is required for both recording and readout.

In this work we introduce a new approach for corner extraction. The method that allows the corner extraction with rotation invariance is composed by a spiral phase function and a binary amplitude. The designed function can be easily implemented as a filter for a Vander Lugt‐like optical correlator. A final image obtained with the detector presents intensity peaks in each corner location. Numerical simulation has been performed on a set of synthetic scenes, modulated either in amplitude or phase. Results that show the very good performance of the method are shown.

An anamorphic white light Fourier processor is used to analyse PIV photographs. The processor is constructed using two holographic cylindrical lenses and one refractive cylindrical lens arranged to correct the longitudinal and lateral chromatic dispersion. By measure the period of the fringes that appear on Fourier plane we can found one component of the fluid velocity along a line of the photograph.

Thin films of tungsten (W) were deposited on opal templates using atomic layer deposition (ALD). Varying fill fractions of W ALD were deposited uniformly inside the opal structure. Fill fractions in the opal were varied from 14% to 79% W ALD to observe variations in the stop band edge location and intensity. The stop band edge was predicted to occur at λ = 432 nm based on the geometry of the W ALD coated opal. No stop band edge was observed at λ = 432 nm for any W ALD fill fraction. These experiments showed that the W coated opal's poor performance was not an issue of W uniformity or fill fraction. The incident radiation in visible region was above the W ALD plasma frequency, thus reducing the reflectivity of the W ALD film. The visible light was transmitted through the W, and was absorbed in a distance too short to allow any Bragg reflections.

Analyzes generates by Scanning Electronic Microscopy (SEM/BSE), Fourier Transform Infrared Spectroscopy (FTIR) and X‐Ray Diffraction (XRD) were used in order to compare epitaxial layers of PbSnTe, grown high quality crystalline by Hot Wall Beam Epitaxy—HWBE technique, directly over single crystal BaF2 wafers, p type. The PbSnTe/BaF2 heterostructures were analyzed electrically by Hall Effect (HE), in electrical contacts in the PbSnTe layers (Van der Pauw method), and optoeletronic by Detectivity (D), are used as thermal infrared detectors that work with the wavelength—3 μm

The fabrication and characterization of planar polymeric waveguides produced on silicon substrate for optical devices is reported. The cladding was made of a fluorinated polymer by CHF3 plasma polymerization and the core was a PMMA film prepared by spin coating. The polymeric waveguides with different widths (from 10 to 100 μm) were patterned by UV photolithography. The plasma fluorinated optical films were characterized by ellipsometry, metricon prism coupler, interferometer and FTIR‐ATR. The waveguide optical characterization was done by coupling a laser beam, fibre‐to‐fibre coupling method, using a multimode optical fibre.

The time reversal phenomenon in sound waves for the discrete case is revisited. Our purpose is to improve a previous explanation of this problem in which there was a more limited scope. We develop a formulation which includes sink terms in the time reversed process, which allow going beyond the diffraction limit. By employing a reversed signal it is possible to reach a definition of a fourteenth of the wavelength. In the present work we discuss a matrix formulation for the discrete case in terms of the Fourier transforms of the input and output signals and the Green function. With this function it is possible to characterize the propagation of signals emitted by an array of devices. We are able to express the time reversed signal and precisely select the destination site, among other useful objectives. Finally we show an experimental arrangement using a Michelson interferometer in order to observe this phenomenon. Time Reversal originates from the second order time derivative in the wave equation. This is different from the case of nonlinear behavior in media known as acoustic or electromagnetic inverse scattering. Some of the fields which Time Reversal opens for investigation are the time reversal of a signal by a sound mirror (Time Reversal Mirror or TRM) or by a Time Reversal Cavity (TRC), and the possibility of sending a message to a precise physical location. Recently a new and powerful application has been reported in the literature, namely the abovementioned overcoming of the diffraction limit in wave physics. Although our experimental proposal is based on reports from others authors, the experimental arrangement used here, the specific way of operation and the image construction are original.

We study the 1D Metallo‐Dielectric Photonic Crystal (MDPC) by two alternative methods, the transmittance and the band structure derived from its dispersion relation. Both approaches have well established exponents on two different regimens, Yablonovitch [1] and Maradudin [2]. We discuss, the particular domain where both formalism coexist and become conveniently complementary. We discuss a MDPC created by a DPC with metallic insets. We find that both, metallic and dielectric features coexist at the band structure as well as the transmittance. We point out how they are related, in particular in that regimen where the applicability of [2] is limited, but we can still draw a relation to understand the complex behavior in [1]. We have carried out the analytical and numerical analysis of a one dimensional metallo‐dielectric stack as a sequence of extremely thin metallic inlays, periodically spaced, preserving the dielectric cell periodicity, on a substrate of two dielectrics that former themselves a PC.

We optimized the characteristics of a silicon quadrant‐type photodiode to operate in the visible region by simulating its fabrication process based on CMOS integrated circuit technology. The design parameters analyzed in this fabrication process are the density of ions and necessary energy for its implantation as well as the temperature and time of thermal treatment. The efficiency of the photodiode was increased by optimizing the density of carriers when phosphor dopants were used. As a result of our optimization process we obtained a pn junction depth of 2.8 μm. In order to absorb most of the energy from the incident photons, within a desired spectral region, the depletion region of our photodiode showed a variation (which depends on the applied direct bias voltage) from 1.22 μm to 7.32 μm. Although our device was optimized to operate with a detection peak of 650 nm, it is possible to detect light in the spectral range from 450 to 850 nm.

Chaos is a class of complex behavior that can emerge from nonlinear dynamical systems, and it exists in both the natural and the technological world. Many biological systems such as the human heart and invertebrate neurons naturally exhibit chaotic behavior. Furthermore, digital computing has made feasible the creation of fractal patterns based on chaos. The beauty of chaos, however, lies not in the aesthetic of fractals, but in the simplicity of the system from which such complex, unpredictable behavior can emerge. The chaotic behavior of a non‐linear R‐L‐Diode circuit has been studied. The non‐linear behavior of the diode was modeled to compare the measured curves with the predicted ones. Period unfolding was observed by feeding the R‐L‐Diode circuit with a sinusoidal signal, varying the frequency and holding constant the amplitude of the input signal. The output voltage was measured on the resistor and bifurcation phenomenon was observed for 2, 4 and 8 periods and for a wide range of frequencies, befor...

This paper showed the development of a transmissible prototype sensor using polymer fiber optic, in order to verify that the optic fiber is capable to transmit the signal through the receptor device and thus use it to obtain the needed parameters in small biological areas. The sensor consists one plastic clip with silicon inside, one infrared (940 nmn) LED (Light Emitting Diode) of 3 mm and one polymer fiber optic with 1 mm of diameter. The control device consists one photodetector with anatomic housing to the optic fiber and one circuit to control the LED emition intensity signal. The photodetector encapsulation is a photodiode with integrated transimpedance amplification. The transimpedance amplification is favorable because reject many noise artifacts. The choice to polymer optic fiber is because the same has a great mobility to twist, eletromagnetic interference imunity and small area to actuated. The interface system was done by LabVIEW software and the device sensor communication with the notebook was USB‐6009 device, both the National Instruments company. The prototype transmissible sensor had the capability to measure the signal doing pratical diagnosis of pathology in biological areas that have small actuated areas.

In this work, we report a simple, flexible method to create long period fiber gratings mechanically by controlling the repulsion/attraction force between two magnets that pressing a plate with a periodic array of small glass cylinders to a short length of optical fiber. Via the photoelastic effect, the pressure points induce the required periodic refractive index modulation to create the LPFG. We found that the induced device exhibits spectral characteristics similar to those of other types of LPFG. As the optical properties of LPFGs are directly related to the nature of the applied perturbations, we show, to our knowledge for the frrst time, how is the evolution of birefringence effects in mechanically induced LPFGs.

The simulation of a tunable dual wavelength birefringent filter is presented with the ultimate goal of developing a novel optical in the terahertz (THz) region of the electromagnetic spectrum for medical applications. THz radiation is located in the electromagnetic around 300 μm. For a long time this frequency domain has been named the “THz‐gap” due to the lack of sources and detector systems. Here we present a novel alternative for a THz laser source based on the novel birefringent filter presented. The filter is constructed using four stages quartz plates placed at Brewster angle. The design of the filter was done using a zero diving angle to facilitate its construction, and the tunability in the overall response of the filter is achieved by rotating only one of the plates. The filter was design to have a center response around 980 nm with the peak separation of 2.50 nm to 3.75, corresponding to frequency separation between 0.8 THz to 1.2 THz, compatible with broadband laser sources in the 980 nm vicinity.

We describe the performance of a diode‐side‐pumped Nd:YLF laser using a compact cavity based on total internal reflection inside the gain media, showing the beam quality improvement with multiple pass configuration. With one pass through the crystal, high efficiency in multimode operation with 6 W of output power for 17.1 W of pump power is demonstrated. Using a second pass through the crystal, the beam quality was improved to fundamental mode with 3.8 W of output power for 17.1 W of pump power.

Both Fresnel diffraction and propagation in second order dispersive transmission lines are expressed by Fresnel integrals and a unified approach of these domains can be developed on the basis of this formal analogy. Spatial curvatures of spherical emitters and receivers, as used in the metaxial theory of diffraction, and temporal chirp functions are shown to be equivalent. As a consequence, results proved in diffraction theory can be transposed to transmission lines; classical formulae that hold true for Gaussian beams have their exact counterparts that apply to Gaussian wave packet propagation in optical fibers. Applications to dispersion compensation in optical communication systems are explicitely described.

An interferometric system of volume optics and fiber optic were constructed and proved, showing the instrumentation technique made for these devices, supported in the new technologies of optical detection, amplification, analogical and digital filtrate and single data acquisition. Based on the Sagnac's effect of volume optics and fiber optic, the interferometer of Sagnac has many applications, nevertheless the methods of construction, design and instrumentation for the sensors manufacture of based on both designs are not very well‐known, is for that reason that in this work approaches some of the methodologies for the design and construction of these devices, obtaining higher sensitivity and better contribution in its respective interferometric paths, for the sensing of different physical parameters in which they are applied. We used the single design for each interferometer, proposing the best detection limit for each one. The data acquisition was made with the proposal to obtain quick results, using the audio card of a PC, obtaining a real time measurements and digital processing of the signal in a single way.

The complex degree of spatial coherence of the optical fields, in general, is a shift variant quantity. Therefore to characterize it, in addition to knowing how it changes in function of the separation of the two points under analysis, we require knowing how it changes in function of the location of these points. In order to measure the complex degree of spatial coherence of any quasi‐monochromatic optical field, we propose a method that uses a mask with a two‐dimensional array of apertures (small circular holes) to sample the optical field. The distribution of the apertures in the mask is made so that we get a non redundant array, it means that the classes of aperture pairs of the mask are composed just by one pair. From the Fourier spectrum of the interference pattern in far field generated by the mask we can determine the magnitude and the phase of the complex degree of spatial coherence. The efficiency of the array is verified with experimental results using a partially coherent beam generated following the rotating glass method. Finally, the results obtained in the experiment are compared with those obtained by means of numerical simulations.

In this work, by means of numerical simulations, we verify that four‐wave mixing (FWM) processes, including depletion and parametric gain, generate a redistribution of pump power in distributed fiber Raman amplifiers (DFRAs). As a consequence of pump‐pump FWM, FWM products are generated, as well as a power exchange between pumps, which produces degradation in the performance of the amplifier due to new SRS‐FWM interactions. Numerical results show impairments in distributed amplified systems due to these interactions, such as loss of flatness on the spectral gain, reduction on the net Raman gain, and presence of strong FWM products within the transmission band.

Nowadays, the problem of water contamination causes the optimization of the processes carried out in wastewater treatment plants to improve the pollutants removal efficiency. In this work, an optical system was implemented to measure the sedimentation speed of sludge in wastewaters, this parameter is very important for designing mechanisms that deposit the sludge in the sediment lower levels of treatment plants. The results obtained with the optical system proposed agree with those obtained using graduate test tube techniques, and provide higher sedimentation speed accuracy.

Recent developments on micro‐structuring of ferroelectric crystals, such as LiNbO3, have opened up new possibilities for several devices in nonlinear and electro optics. In this paper, after describing the basics of LiNbO3 based integrated electro‐optic modulators, we will show how techniques such as etching, domain inversion and thin film processing can be used to realize new geometries which can take the performance to unprecedented levels. In particular we will report recent results on the use of domain inversion on a micron scale to tailor and improve the electro‐optic response of LiNbO3 waveguide modulators, showing that these applications for domain inversion techniques might be even more important and commercially valuable than those in nonlinear optics (e.g. quasi‐phase‐matched optical parametric devices). With respect to standard single‐domain structures, larger bandwidths and lower driving voltages can be obtained, thus achieving figure of merits for the electro‐optic response that are up to 50%...

The necessity of detection and recognition of different types of gases, such as simple volatile organic compounds or their mixtures, requires the development of different types of sensors and the study of different materials for sensing films. In this work, an application of an optical fiber to the detection of VOC is presented. The sensor was constructed removing a portion of the cladding of approximately 3 cm and depositing instead a sensing titanium dioxide (TiO2) film doped with an organic dye (rhodamine 6 G) by the sol‐gel technique. The sensor operation principle is based on the absorption of evanescent wave when the sensing film interacts with the VOC molecules, which attenuates the output optical power. The difference between the output power with and without gas gives a measure of the concentration in the chamber. The results showed that for ethanol concentration from 0 to 10,000 ppm, the response of the sensor was approximately linear. The sensor responses to octane and ethyl acetate were also studied.The necessity of detection and recognition of different types of gases, such as simple volatile organic compounds or their mixtures, requires the development of different types of sensors and the study of different materials for sensing films. In this work, an application of an optical fiber to the detection of VOC is presented. The sensor was constructed removing a portion of the cladding of approximately 3 cm and depositing instead a sensing titanium dioxide (TiO2) film doped with an organic dye (rhodamine 6 G) by the sol‐gel technique. The sensor operation principle is based on the absorption of evanescent wave when the sensing film interacts with the VOC molecules, which attenuates the output optical power. The difference between the output power with and without gas gives a measure of the concentration in the chamber. The results showed that for ethanol concentration from 0 to 10,000 ppm, the response of the sensor was approximately linear. The sensor responses to octane and ethyl acetate were also s...

In this paper we demonstrate a tenfold pulse power enhancement by operating the Er:YLF laser at the strongly modulated relaxation oscillation region, at 3 μm wavelength. We obtained 1.2 W of average power for 250 μs pulse duration and up to 400 Hz of repetition rate for a 6.8 W, jitter free, single spike with nearly Gaussian temporal shape without any kind of intracavity Q‐switching device.

We study numerically the behavior of bright periodic lattices in negative nonlinear medium. We use two‐dimensional nonlinear Schrodinger equation, and the solutions are found with split‐step method. The critical parameters are the periodicity, the nonlinear constant, and the size of the each spot of the periodic lattice array. We found that bright spots interact with neighbors during the all distance of propagation. The negative refractive index of the medium, produce diffraction in bright spot of the light, in consequence, each spot of the light interact with the four close neighbors and the darks spots are self‐focused. The initial period of the array selected, determine the behavior of the dark periodic arrays. We find two regions of interest of the dark periodic lattice pattern: circular dark lattices and linear dark periodic lattices. The evolution of the two‐dimensional bright periodic lattice to one‐dimensional periodic lattice is due to self‐phase modulation of the beam. These numerical results ar...

The objective of the paper is to determine the coordinates of the dominant colors in complex digital images. The key issue is the selection of an appropriate color space and optimal quantization of the selected color space. Five color spaces, RGB, LCh, Lab, I1I2I3 and HSI, and several quantization levels are involved in evaluating the performance of the propose method. The method is based on the local detection of the maxima of the color histogram. It is analyzed how the quantization and the size used in the localization of the maxima affect to the number of dominant colors obtained and their color coordinates. First, a group of twenty eight images has designed itself test. The objective of using images test is to be able to compare the coordinates of the dominant colors that the method provides with the expected values. This allows evaluating what color space provides smaller mean square error in the calculation of the color coordinates of the dominant colors, as well as their area. They have been design...

The simulation, fabrication and characterization of Anti‐Resonant Reflecting Optical Waveguides (ARROW) using dielectric films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique at low temperatures (∼300 °C) are presented in this work. For numerical simulations, home‐made routines based in two computational methods were developed: the Transfer Matrix Method (TMM) used for the determination of the optimum thickness values of the Fabry‐Perot layers, and the Finite Difference Method for 2D design and determination of the maximum width which allows single‐mode operation. Also, since the simulations showed that the utilization of high refractive index differences between the core and the first ARROW layer produce lower optical attenuations, amorphous hydrogenated silicon carbide (a‐SiC:H) films were used as first cladding layer. These films present refractive index values greater than Si3N4 films (material commonly used as first ARROW layer). Furthermore, silicon oxynitride (SiOxNy) films...

In this work we analyze the Farnsworth Munsell 100 Hue Test results, this test offers a simple method for testing color discrimination and was applied to a sample of 129 observers, with natural daylight in the same conditions (the observers were men and women), all of these were participants in colorimetric training courses, and aged 20 to 76, with two to twenty five years experience in the color control manufacturer laboratories (of plastics, rugs, dyes, textiles, and paints). Their job titles included mixers, inspectors, shaders, matchers, passers, and dyers. The test was applied twice and the results here presented are the comparison between both tests, taking into account errors by mistakes incidence in each hue position, as well as the redeeming of each participant in both test. The comparison shows us that most of the mistakes are in the green hue in both tests, but in the second test, approximately 20 percent of the observers reduced those. Also we can to separate persons with normal color vision of those which have zones of color confusion. In this work it is show some ones results of the comparison between men and women.

The conception of a tridimensional digital model of solid figures and plant organs started from topographic survey of virtual surfaces [1], followed by topographic survey of solid figures [2], fruit surface survey [3] and finally the generation of a 3D digital model [4] as presented by [1]. In this research work, i.e. step number [4] tested objects included cylinders, cubes, spheres and fruits. A Ronchi grid named G1 was generated in a PC, from which other grids referred as G2, G3, and G4 were set out of phase by 1/4, 1/2 and 3/4 of period from G1. Grid G1 was then projected onto the samples surface. Projected grid was named Gd. The difference between Gd and G1 followed by filtration generated de moire fringes M1 and so on, obtaining the fringes M2, M3 and M4 from Gd. Fringes are out of phase one from each other by 1/4 of period, which were processed by the Rising Sun Moire software to produce packed phase and further on, the unpacked fringes. Tested object was placed on a goniometer and rotate to generat...

The application of projection moire with phase shift techniques in vegetable organs surface topography survey had to step up basic procedures before reaching significant conclusions. As recommended by [1], the proposed method should be tested on virtual surfaces [1] before being carried on solid symmetric surfaces [2], followed by tests on asymmetric surfaces as fruits [3] and finally a generation of a 3D digital models of solid figures as well as of fruits [4]. In this research, identified as the step [2], tested objects included cylinders, cubes and spheres. In this sense a Ronchi grid named G1 was generated in a PC, from which other grids referred as G2, G3, and G4 were set out of phase by 1/4, 1/2 and 3/4 of period from G1. Grid G1 was then projected onto the samples surface instead of being virtually distorted, receiving the name of Gd. The difference between Gd and G1, G2, G3, and G4 followed by filtration generated the moire fringes M1, M2, M3 and M4 respectively. Fringes are out of phase one from each other by 1/4 of period, which were processed by the Rising Sun Moire software to produce packed phase and further on, the unpacked fringes. Final representations in gray levels as well as in contour lines showed the topography of the deformed grid Gd. Parallel line segments were projected onto moire generated surface images to evaluate the approximation to the real surface. Line segments images were then captured by means of the ImageJ software and the corresponding curve fitting obtained. The work conclusions included the reliability of the proposed method in surveying solid figures shape.

The organic molecules of a chain structure containing phenyl, oxazole and oxadiazole rings are used in different combinations as active media for tunable lasers. From this viewpoint, we focused in the theoretical study of organic compounds of three rings, which have similar optical properties (fluorescence and laser properties). The main goal of this study is to compare the electronic structure through the analysis of molecular global descriptors defined in the DFT framework of2‐[2‐X‐phenyl]‐5‐phenyl‐1,3‐Oxazole, 2‐[2‐X‐phenyl]‐5‐phenyl‐1,3,4‐Oxadiazole, and 2‐[2‐X‐phenyl]‐5‐phenyl‐furane with X = H, F and Cl. The basis set used was 6−31G+(d).