In this work we present the synthesis of Au@Ag bimetallic nanoparticles via seed-mediated method and their nonlinear optical properties. For the synthesis of nanoparticles, 18 nm gold seeds were synthesized by Turkevich method followed by the silver ion reduction with ascorbic acid. The nanoparticles dispersion was analyzed by UV-Vis spectroscopy and the spectra suggest the formation of spherical core@shell bimetallic nanoparticles. SEM images were obtained in order to corroborate this. The nanoparticles dispersions present negative and positive nonlinear absorption coefficient and negative refraction index, according to z-scan measurements. The nonlinear optical properties can be tailor modifying the thickness of shell.
Physical and optical characterization of thin films doped with Au Nanoparticles onto a silica substrate is presented. Films were prepared through sol-gel process, by using Au nanoparticles immersed in lipoic acid as dopant by means of hydrolysis and acid catalyzed reaction of tetraethyl-orthosilicate. The surface was characterized by SEM and AFM microscopies. Z-scan technique was used to measure nonlinear optical properties as nonlinear absorption and refraction indexes, using two different wavelengths. At 633 nm it was possible to observe nonlinear absorption only but at 514 nm both nonlinear properties were observed.
Characterization of thin films doped with organic metal materials onto a silica substrate is presented. Films were prepared through sol-gel process, by using macrocycles with Cu as dopant by means of hydrolysis and acid catalyzed reaction of tetraethylorthosilicate. Z-scan technique was used to measure nonlinear optical properties, nonlinear absorption and refraction indexes.
High intensities electromagnetic energy interacting with organic media gives rise to nonlinear optical effects. Hibiscus Sabdariffa is a flower whose concentrated solution presents interesting nonlinear optical properties. This organic material shows an important self-phase modulation with changes bigger than 2π. We present a diffraction ring patterns study of the Hibiscus Sabdariffa solution. Numerical results of transmittance, with refraction and simultaneous absorption, are shown.
In this work, the fabrication of thin films mixed with cholesterol enzyme as recognition component is shown, using solgel technique. The film was deposited at one end of photonic crystal fiber (optrode), which was used as carrier medium of sol-gel matrix. The concentration of cholesterol in the test sample was determined by the use of transmittance. Measuring device consists of a power source (laser diode), optrode and a light detector. The laser beam is transmitted through the optrode; the variations of intensity depending on cholesterol concentration are emitted to be detected by a photoresistor.
Research of nonlinear optical properties of materials for manufacturing opto-electronic devices, had a great growth in the last years. The solutions with nanoparticle metals present nonlinear optical properties. In this work we present the results of characterizing, analyzing and determining the magnitude and sign of the nonlinear refractive index, using the z-scan technique in solutions with nanoparticles of gold, lipoic acid and sodium chloride. We used a continuous Argon laser at 514 nm with variable power, an 18 cms lens, and a chopper. We determined the nonlinear refractive index in the order of 10-9. These materials have potential applications mainly as optical limiters.
In this work we present the study of nonlinear optical properties of Au nanoparticles suspended in different solutions, using the z-scan technique. Thermal lens model and Shiek-Bahae formalism were used to determine the nonlinear properties. Parameters as the sign and nonlinear refractive index n2 , nonlinear absorption coefficient (β) and dn/dt were found. Analyses of changes in these parameters using different solutions with the same concentration of Au nanoparticles are shown.
Research nonlinear optical properties of the materials for the fabrication of opto-electronic devices have growth in the last years. Ionics liquids present nonlinear optical properties. In this work we present the results of nonlinear optical properties of four ionic liquids of 1-methylpyrrolidine family, analyzed using a z-scan technique. The results show the difference obtained using or not a chooper for measuring the nonlinearity and the photoinduced lens. Ionic liquids have a negative nonlinearity (self-defocusing) of thermal origin.
In this paper, design of optrodes of photonic optical fiber to a pH sensor with a pH dye is described. The sensor is prepared by immobilizing blue bromophenol, as a pH dye, using sol-gel technique with a photonic optical fiber. The physical principle is based in the absorption of the optrodes of the light from a laser diode as an emitter, and as transducer we use a photoresist for electronic conditioning of the signal.
In this paper we shows the results obtained to fabricate and implement Mach-Zehnder interferometers of
conventional fiber optic using Long Period Fiber Gratings (LPFG´s) which were developed by electric arc
technique. We obtains this type of interferometer when we fabricated two LPFG’s in series or in cascade with the
same characteristics such as number of discharges and the same period, placing them in cascade separated by a
distance which three times the length of the LPFG. The application which was given at interferometer fabricated
was as a liquids sensor, volume sensor of liquids and micro-displacement sensor. The sensors of liquids and liquids
volumes were placed in a container in which the interferometer is fixed so that results of measurements are only by
incorporating each of the liquid and not by some external movement. The sensed fluids were: water, alcohol and
solution (water with sugar). Final length of the interferometer is between 4 to 6 cm. We analyze the results obtained
to when a section the Mach-Zehnder interferometer is displaced in of the order of microns. The variations observed
in transmission spectra obtained from each of the sensors mentioned, show changes in the amplitude and the
attenuation peak of the interferometer was displaced.
We present an experimental study of light polarization on solid core microstructured optical fibers type (Large Mode
Area) LMA-16, LMA-20 and LMA-25. These fibers were partially filled with one micron diameter polyethylene spheres
or carbon nanotubes diluted in distilled H2O by capillarity. Polarization characterization was realized on these Photonic
Crystal fibers with air filled holes and partially particle filled holes using a He-Ne 633nm central wavelength laser at
10mW. The achieved results were compared using graphical data of every test collected at different exposition dates
where the fiber was exposed to particle sedimentation. Results depicted that short time sedimentation of these particles
does not change the light polarization leaving from the fiber except for the phase of the beam. On the other hand, longer
time particle exposition visibly changes the light phase measured at the end of the photonic crystal fiber with repeatable
results.
We prepare optrodes of fiber optic plastic with sol-gel technique. Suitable concentration of carbone nanotubes (CNTs),
phenol red, bromophenol blue and cresol red, design optrodes with fiber optic plastic. The surface charge of silica and
the refractive index, which play an important roll on the fiber, modifies the conditions of light propagation into the
plastic optical fiber. We use the transmittance to measure the pH of a solution or fluid in a range between 3 and 9.
We propose a new method for mass production of the photonic crystal devices on the basis of widely-known and well-developed technology such as micristructured optical fibers. In this paper, we investigate the optical properties of side-excited microstructured fiber and discuss the conditions for utilization such a structure as planar photonic crystal device, namely, the high-quality resonance filter.
We propose the fabrication and characterization to bending and temperature of a long period fiber grating with the
alternative electric arc method known as fattening. This is the enlargement of the fiber structure by means of arc
discharges from a commercial splicing machine. The fiber structure consists of 4 layers of glass of different refractive
index. The resulting device is a reject band filter with an attenuation band around 1400nm. It has a bandwidth of 162nm
with a depth around 26.9 dB. Test to bending depict changes in band depth up to -10dB between radii values of 4-7cm
with a shifting span of 16.8nm. Temperature characterizations are made with bending and straight fiber over a hot
surface. Interesting achievements can take advantage as optical sensors with different characteristics. Optimization in the
fabrication process can be achieved to lower the insertion losses so better sensors can be applied for industry and
commercial applications.
In this work an investigation into the viability of a dual gas sensor based on correlation spectroscopy using a single
Fabry-Perot Interferometer (FPI) is presented. Here, based on sensor response simulations, it is demonstrated that the
commonly considered undesirable effect due to multiple internal reflections of the FPI's mirror substrate can be used to
increase the sensing capability of the system. Usually designers tend to minimize these reflections to improve the FPI
transmission spectrum. However we let them to occur in order to used them as a part of the modulation system of the
sensor which allows us to detect two gases simultaneously using a single FPI.
In this work we present the modal study of a dispersion shifted fiber (4 layers) and also in a fabricated long period
grating in the same fiber type using the RSoft Software ®. For the grating analysis, the refraction index and the
diameters were varied to simulate the changes due to the diameter increment provided by the electrical arc discharges
effect. The structural optical fiber change, due to the periodic fattening induced by the electric arc, is added to the
grating analysis as a sinusoidal type variation in each optical fiber layer. Several wavelengths are considered for the
analysis and some of them are the ones commonly used by operational lasers and diodes launched in optical fibers.
Results depicted the existence of many excited light modes when working with a wide spectrum white light source.
When these modes satisfy the phase matching condition, they will couple in the LPFG providing it of particular filtering
characteristics because of the fiber type and technique (fattening) of fabrication.
In this work, we show results about the nonlinear optical characterization for four ionic liquids (ILs), namely 1-buthyl-3-
methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-ethyl-3-methylimidazolium Bis((trifluoromethyl)sulfonyl)imide
([EMIM][TF2N]), 1-ethyl-3-methylimidazolium trifluoroacetate ([EMIM][CF3COO]),1-buthyl-3-methylimidazolium
trifluoroacetate ([BMIM][CF3COO]), using z-scan technique.
Nonlinear effects are consequence of interaction of height intensities of energy with the matter. Self-diffraction is
nonlinear effect and rings are produced. We analyzed the increase of rings due to changes in intensity of CW Ar laser
that modify the nonlinear refractive index. The Carbon Nanotubes (CNTs) were dispersed on different solvents: a) water,
b) ethanol, c) isoprophanol, and d) acetone. The concentrations were 10ml:1mg in all samples. The dependence between
power and concentration of CNTs is shown.
In this paper we propose a high voltage source which is controlled by a communication port I/O of a data acquisition
card. The graphical programming language LabView is employed for this task. We make use of this source to produce
optical fiber gratings by inducing an electric arc with the point by point procedure. It has a control section to modify the
arc duration time and thus the voltage and current applied to the fiber by means of two electrodes. The experimental
setup by which we characterized the gratings is depicted and we also present the transmitting spectrum. The gratings
were fabricated with SMF-28 fiber but microstructured fiber can be exploited too. These gratings can be used with
optical fiber lasers as optical filters and in the implementation of optical sensors.
Annular Photonic structures, which occur on bulk and fibers, are Bragg structures that share both Bragg resonances and waveguiding. They are related to Photonic crystals because of their large enough refraction difference indexes (n2 - n1) that makes unavoidable to consider in full the reflected wave, well beyond the approximations required for analytical gap solitons. Effectively, their confining capabilities are or primary importance, however, the potential of those structures are substantial and deserves to be further explored. Waveguiding occurs where the structure is homogenous, and may be handled on well known methods. Nonlinear propagation has been observed on solid core Bragg fibers and the soliton distribution on a nonlinear circular and annular region have been described. Linear Photonic annular structures, such as resonators, have been studied by A. Yariv as well as on omniguide fibers. The propagation along the direction where the material is inhomogenous, and that correspond to the beam profile, is a complex task and it is the objective of this paper.
KEYWORDS: Sensors, Magnetism, Optical fibers, Magnetic sensors, Mirrors, Data conversion, LabVIEW, Telecommunications, Distance measurement, Chemical elements
In this work the implementation of a sensor of optical fiber current is reported by means of a magnetic structure. The sensing element (magnetic structure) consists of a magnet placed in the center of a plastic membrane. The variation in the intensity of the light caused by a mirror adapted to the membrane allowed to detect the changes in the presence of a magnetic field produced by an alternating current. Its changes were detected optically. We design a circuit to convert the light to equivalent in data to be process by a PC. The data are read and by means of a program in software Labview, is the equivalent of current according to the intensity of detected magnetic field.
Design and characterization of a pH optical fiber sensor with a pH sensitive dye is described in this paper. TEOS (Tetra-ethyl-Orto-Silicate) was used to dope a plastic optical fiber, which will be used as the probe. The sensor is prepared by fixing the doped plastic fiber on a fused ortosilica block surface with blue bromophenol. The fiber surface charged with silica and the refractive index, which plays an important roll on the fiber, modifies the conditions of light propagation into the plastic optical fiber. The fiber transmittance is used to measure the pH of a solution or a fluid in a range between 7 and 10.5. Such signal is captured by a photodetector and processed with a LabView development environment which also controls a hardware designed in our laboratory. The advantage of this system is that 2cm of doped fiber are enough to measure the pH of a fluid in real time. The response time of this system is approximately 10s.
We present the polarization dependence in the formation of dark spatial waveguides in nonlinear liquids like CS2. Our experimental and numerical results about the formation of dark waveguides show the dependence between the polarization and the formation of multiple waveguides. With a polarization angle between 100° - 120° for the incident beam we show that the wide of the waveguide is minimum and even dark spatial waveguides are formed. A discussion about waveguides formation is presented for others polarization angles. In this work we show an improvement in the method to measure low birefringence in optical fibers.
We present the control of the monochromator DK240 developed by a program in LabVIEW, this program adjusts the entrance/exit slits, the scan of the measurement of the wavelength in a range from 100 nm to 3000 nm as well as the scan speed, we also show experimental setup to measure the absorption of Erbium-Doped Fiber and its experimental graph.
In this work we showed an improvement in the method to measure low birefringence in optical fibers with the Sagnac interferometer published in paper previous in which the fiber twists in an end of the loop of the interferometer and the entrance of the light every time it is adjusted that twists the fiber. In this work we twist the fiber in the center of the loop of the Sagnac interferometer it is very simple and we don't need light polarization neither to adjust the axes in the entrance of the fiber. It can use for the mensuration a section of shorter fiber that a beat length. Some theoretical and experimental results are presented.
This paper is about a numerical investigation of the NOLM (non optical loop mirror) with low birefringence fiber and a 0.5/0.5 coupler. We induce birefringence to the loop fiber bias macro bendings considering self-rotation polarization of the input beam. This is done in order to find its possible advantages as an optical switch.
The chirping of a pulse propagating on a nonlinear media is nowadays a rather well studied phenomena and we are aware that requires an appreciable propagation length to develop. A nonlinear stack of finite dimension, does not have those dimensions. Therefore, chirping in this media is a rather new feature that deserves to be studied at considerable length given the greater importance that those structures have in photonics. We present a nonlinear analysis of a finite stack, nonlinear at each media and compare it with its analytically solvable linear case. The pulse propagation is discussed, in particular we demonstrate intensity dependence of the chirp as a distinctive nonlinear signature. We show two additional nonlinear characteristics: the nonlinear switching and the bistability.
The Sagnac interferometer of twisted low-birefrigence fiber is analyzed numerically in the lineal region. A method for measuring the birefringence of the fiber and the angle of rotation of the axes inside the fiber loop of the interferometer is also presented.
In this work we have shown that Stimulated Raman Scattering can be effectively controlled by a fiber bending losses resulting in spectral dependence of the fiber attenuation.
We analyze linear and no linear optical properties of PMMA clusters in thin film s with Ni nanoparticles dispersed with different concentrations. Saturable absorber and negative nonlinear refraction index behavior evidences were found using z-scan technique. We also show that these properties have not dependence of the type of matrix but they have on concentration.
An experimental investigation of the dynamical, time depends effects in the reflection of (2+1)D beam at the nonlinear interface between photorefractive crystal SBN61:Ce and a linear medium is performed. Our study make emphasis on determining the physical condition under which the beam reflected by the interface is still a focusing beam.
This paper proposes a neural network-based technique for improving the quality of the image fusion as required for the remote sensing (RS) imagery. This proposes to exploit information about the point spread fucntions of the corresonding RS imaging systems combining it with prior realistic knowledge about the properites of teh scene contained in the maximum entropy (ME) a priori image model. Applying the aggregate regularization method to solve the fusion tasks aimed to achieve the best resolution and noise suppression performances of the overall resulting image solves the problem. The proposed fusion method assuems the availability to control the design parameters, which influence the overall restoration performances. Computationally, the fusion method is implemented using the maximum entropy Hopfield-type neural network with adjustable parameters. Simulations illustrate the improved performances of the developed MENN-based fusion method.
Most of the optics measurements techniques used generate interferograms as a result. These give us information about the object's quality, surface, etc. Evaluating and knowing the heat gradient of an object, is a typical application of the interferograms analysis. We know that if we subject an object to heat, this will generate interferograms, in which the fringes form will be temporal, the deformation of the fringes tel us the temperature gradient, but it doesn't give us the temperature level of the object. In order to obtain this level we sampled interferograms in different intervals and we count the number of fringes in every sample interferogram. With this process we make a characterization that provide the temperature level change in an object. In order to acquire the interferograms we used the National Instruments IMAQ-1408 board and the software was designed in LabView.
The neural network-based technique for improving the quality of the image fusion is proposed as required for the remote sensing (RS) imagery. We prose to exit information about the point spread functions of the corresponding RS imaging systems combining it with prior realistic knowledge about the properties of the scene contained in the maximum entropy (ME) a priori image model. Applying the aggregate regularization method to solve the fusion tasks aimed to achieve the best resolution and noise suppression performances of the overall resulting image solves the problem. The proposed fusion method assumes the availability to control the design parameters, which influence the overall restoration performances. Computationally, the fusion method is implemented using the maximum entropy Hopfield-type neural network with adjustable parameters. Simulations illustrate the improved performances of the developed MENN-based image fusion method.
We study numerically the behavior of (1 + 1)D spatial solitons in a nonlinear interface under drift and diffusion nonlinearity. In this report, we analyze the influence of parameter like diffusion nonlinearity of the medium leading to the beam self-bending effect.
The basic concept of robustfield maximum likelihood (ML) method for identification of the parameterized model of the multipath communication channels with scattering is introduced as required for communication channel modeling. Employing the descriptive regularization in the ML estimation strategy performs the robustification of the ML estimator. The proposed robustfield ML parameter estimation algorithms when used in the space-time identification of the models of the communication channels has an advantage over the conventional ML estimator because it permits the identification of the channels with closely spaced multipaths. The formulae for the Fisher's information matrix and Rao-Cramer bounds for the variances of the ML estimates of the parameters of interest of the multipath signal are derived.
We study experimentally the behavior of 1D and 2D spatial solitons in a SBN61:Ce photorefractive crystal under drift nonlinearity. In this report, we show experimental observation of optical branching effect for 1D beams and anisotropic self-focusing effect for 2D beams when we applied an appropriate external electric field along the c- axis of the photorefractive crystal.
In this work we address our attention to the implementation of a beam analyzer. The software was designed under LabView, platform and using the Image Acquisition Card IMAQ of National Instruments. The objective is to develop a graphic interface which has to include image processing tools such as characteristic enhancement such as bright, contrast and morphologic operations and quantification of dimensions. An application of this graphic interface is like laser beam analyzer of medium cost, versatile, precise and easily reconfigurable under this programing environment.
In this paper we report the linear and non-linear properties for PMMA films clusters with nanometrical
Silver particles. These samples were prepared by bulk polymerization of methyl metacrylate solution of silver trifluoracetate
and followed by post-heating. Varying the concentration ofparticles and using different thermal procedures shown different
properties. Third-optical susceptibilities were measured
We study the reflection of two-dimensional spatial solitons at the nonlinear interface between a saturable nonlinear medium
(photorefractive crystal) and a linear medium. Our study places emphasis on determining the experimental conditions under
which the beam reflected by the nonlinear interface is still a spatial soliton.
We present a numerical study of the reflection of 1D spatial solitons at non-linear interface between a photorefractive medium and a linear medium. In this work, we have considered that non-linear medium is governed by both; drift and diffusion mechanisms. Our study places emphasis on determining the physical conditions under which the beam reflected is still a spatial soliton. The beam is deflected into the interface using the self-bending effect.
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