Grupo de Nanofotonica
Permanent URI for this collectionhttp://48.217.138.120/handle/20.500.12272/1241
Browse
Item Molecular rotational diusion detected by dierential fluorescence energy(2000-03-01) Torga, Jorge Román; Marconi, Mario; Negri, Martin; Aramendia, PedroIn this paper, we present a complete study of the influence of the molecular rotational diffusion movement in the fluorescence signal when a sample is excited by two short pulses. The study includes the calculations of this effect for ellipsoidal molecules. Experimental results are presented that show a fluorescence behavior influenced by the molecular rotational diffusion movement with temporal characteristics that agree with our calculations.Item Fast scanner with position monitor forlargeopticaldelays(2001-11-01) Constantino, Santiago; Martínez, Oscar; Torga, Jorge Román; Do Campo, P.; Libertiun, A.R.Wepresent a new fastscansystemthatemploys a stepper motor used in a single steposcillatingmode and a position monitor devicebasedon a diode laser. Thesetupusedgeneratesdelays as large as 105 ps at 10 Hz, with 100% dutycycle. Wealso introduce a reliabledevicebasedontheshadow of a movingcutterwith a laser diode as the light source to avoidpowerfluctuationsproblems.Item Wide band interferometryforthicknessmeasurement(2003) Constantino, Santiago; Martínez, Oscar; Torga, Jorge RománIn thisworkwepresentthe concept of wide band interferometry as opposed to white-light interferometry to introduce a thickness measurementmethodthatgainsprecisionwhenthebandwidthisreduced to anadequatecompromise in order to avoidthedistortionsarisingfromthe material dispersion. The use of thewidestpossible band is a well established dogma whenthehighestresolutionisdesired in distance measurementswithwhite-light interferometry. Wewill show thatthe dogma fallswhenthicknessmeasurementsmust be carriedoutdue to material dispersion. In factthe precise knowledge of thefrequencydependence of therefractiveindexisessentialforadequatethicknessretrievalfromthe opticalexperiments. Thedevicewepresentisalsouseful to obtainthegroup refractiveindexthatisnecessary to calculatetheabsolutethicknessvalue. As anexample, we show thespreading of a siliconeoilon a reference surface in real time.Item Simultaneous measurement of deformation and thickness change in polymer films(2006-08-14) Torga, Jorge Román; Morel, Eneas NicolásWe present experimental results in deformation measurement and thickness change in polymer films employing Fourier domain interferometry. The set-up is a Michelson configuration in which interference signal betweeen light reflected from a reference arm is superposed with two reflection from the first and second interface from the film sample. Distance measurements for determination of deformation and thickness values were obtained after an inverse Fourier transform of the spectrum signal. With this configuration, measurements with 1 micron axial resolution, and 2mm dynamic range were obtainedItem Limitations due to the detector in the low coherence interferometry(2008-02-15) Morel, Eneas Nicolás; Torga, Jorge RománSe describirá como se generan las señales de interferometria de baja coherencia en el espacio de Fourier, se determinara las características que determinan el rango dinámico del sistema y las señales asociadas al sistema de detección y su influencia en la señal de interferencia.Item Simple method for thickness measurement in opaque samples with a Michelson-Sagnac interferometer(2008-04-24) Morel, Eneas Nicolás; Torga, Jorge RománWe present in this work a method to measure thicknesses of opaque samples. The technique combines the use of low coherence interferometry with a Michelson-Sagnac configuration. This ring set-up let us to measure both faces of the sample simultaneously. So it is possible to obtain the thickness by measuring the optical path difference between a reference and both surfaces of the sample. Experimental results up to 1mm are shown in metal gauge block. A resolution better than 10 micronswas obtained.Item Characterization of reference standards for dirt by Laser Ablation Induced Photoacoustics (LAIP)(2009-07-23) Orzi, D.J.O; Morel, Eneas Nicolás; Torga, Jorge Román; Ravigioni, A.N.; Bilmes, G.MMeasurements of surface cleanliness and dirt characterization are important problems in a wide range of processes in industry and production. Standard methods are in most cases cumber some laboratory procedures that must be performed out of the production lines. Instruments and methods for clean liness determination and dirt characterization require reference standards for calibration. For that purpose we built a possible dirt reference standard (DRS) made by films of graphite greases ubjected to heat treatment for mechanical stabilization. The DRS characterization was performed by Laser Ablation Induced Photoacoustics (LAIP). The measurement of the thickness of the films was made by low-coherence interferometry.Item Plasmon-induced photochemical synthesis of silver triangular prisms and pentagonal bipyramids by illumination with light emitting diodes(2013) Scarpettini, Alberto; Roldán, Virginia; Bragas, Andrea; Bordenave, Martín; Pellgri, NoraWe have grown silver prisms and pentagonal bipyramids, induced by plasmon excitation on a colloidal solution under the irradiation of light emitting diodes of different colors. Two methods of synthesis of the seeds were tested and their growth evolution recorded, in order to analyze the effect of the chemical synthesis and the color of the irradiation on the morphology and size of the final product. We show that the conversion rate into anisotropic nanoparticles is determined by the chemical environment and the shift of the irradiation wavelength with respect to the plasmon resonance of the seeds. The conversion rate defines the final morphology of the nanoparticles, whereas the size of the nanoparticles is univocally determined by the wavelength of irradiation, irrespective of the method to prepare the seed solution.Item Optical coherence tomography-based scanning system for shape determination, wall thickness mapping, and inner inspection of glass containers(2013-02) Morel, Eneas Nicolás; Gutierrez, Marina; Miranda, Hernán; Sambrano, Edgardo; Torga, Jorge RománIn this work we present a method that enables simultaneous measurement of shape and wall parameters of glass containers. The system is based on the optical coherence tomography technique, employing the spectral domain configuration. The data were obtained by measuring the spatial coordinates of a sequence of points in a predefined region of a sample that includes points on the surface and in the interior of the material. Dimensional parameters, thickness mapping, and tomography studies of the interior of the sample walls can be obtained from these measurements.Item Scanning optical coherence tomography applied to the characterization of surfaces and coatings(El Sevier, 2014) Cerrotta, Santiago; Morel, Eneas Nicolás; Torga, Jorge RománThis paper shows the technique of optical coherence tomography in the frequency domain (OCT-FD) to obtain surface topography and tomography of surface coatings. The setup is based on a superluminescent diode centered on 849 nm with an spectral wide of 50 nm as the light source, a single-mode fibre Michelson interferometer and a spectrometer as the detector system. This scheme allows having compact and robust equipments that was designed to be used in an industrial environment. With this system it can be obtain a tridimensional image acquired point by point with a maximum range of 20 mm width and length and 2 mm depth. Images obtained from the topography of metal samples and tomography of polymer based coatings is presented. Also it is shown that is possible to obtain, from these images, parameters of interest of the sample, such as roughness, flatness and characteristic distances. As an example to show the potential of the method the dimensions of a metal surface modified after laser ablation were measured from a topography image obtained with this technique. A second example presented was the image obtained of a roughness pattern made on a metal surface. Finally it was presented a tomography image of a modified polyurethane coating deposited on a metal surface. Thickness and refractive index of the coating were obtained after the image analysis.Item Diseño y construcción de un módulo de microscopía de barrido por sondeo local y de un sistema de nanoposicionamiento de alta precisión para un microscopio multianálisis(2014) Martínez Reina, Hernán; Pujol, Miguel A.; Morel, Eneas Nicolás; Scarpettini, Alberto; Torga, Jorge RománEste trabajo presenta la técncia de interferometrá de baja coherencia orientada a la obtención de topografiá de superficies y tomografía de materiales. Se decribe la idea general, se presentan distintos esquemas experimentales y se muestran resultados obtenidos en distintos tipos de aplicaciones. Se pretende mostrar que esta técnica, todavía en etapa de laboratorio, puede ser en muchos casos una alternativa a las técncias convencionales o una solución a problemas por resolver, en el área de los ensayos no detructivos en materiales.Item Cabezal óptico compacto aplicado a la medición de vibraciones sin contacto(Cuarto Congreso Argentino de Ingeniería Mecánica – CAIM 2014, 2014) Aguilar, Andres; Morel, Eneas Nicolás; Torga, Jorge RománEn este trabajo presentamos un cabezal óptico diseñado para medición de vibraciones basado en la señal de error de foco (SEF), la misma utilizada para leer datos en un cabezal láser de DVD o CD. El sistema fue diseñado con la motivación de obtener un dispositivo compacto y robusto, de bajo costo y pequeñas dimensiones, que pueda ser usado para medir múltiples puntos y sin contacto con la muestra. El CO presentado en este trabajo mide la posición absoluta entre el plano focal del sistema óptico y el punto iluminado en la muestra. Dado que la SEF es dependiente de la reflectividad de la superficie muestra es necesaria una calibración previa, por eso el sistema incorpora un actuador piezoeléctrico que le permite realizar calibraciones in situ y obtener medidas temporales de la posición. Con este esquema se midieron vibraciones con una amplitud de hasta 10 μm y una frecuencia de hasta 1 KHz. con una resolución espacial mejor que 0.5 micrones. Se presentan resultados experimentales en vibraciones de una superficie generadas con un sistema controlado por un elemento piezoeléctrico y en vibraciones transversales generadas en una barra metálica.Item Caracterización de recubrimientos obtenidos a partir de film líquidos por interferometría de baja coherencia.(2015) Sallese, Marcelo; Morel, Eneas Nicolás; Lunaa, Georgina; Tabla, Pablo; Torga, Jorge RománEn este trabajo se presenta la interferometría de baja coherencia como una técnica sin contacto para caracterizar recubrimientos obtenidos a partir de un film líquido depositado sobre distintos materiales. Nos referimos específicamente a recubrimientos poliméricos, barnices, pinturas y lacas entre otros, con la única condición de que sean transparentes o semitransparentes en la región del espectro electromagnético en el rango entre el visible y el infrarrojo lejano (400nm a 2000nm). La técnica permite la medición de espesor y homogeneidad del recubrimiento, o sea que puede ser utilizado como técnica de monitoreo del producto final o para estudio de su evolución temporal en el proceso de formación del film, por ejemplo en procesos de secado, polimerización o cambios estructurales. Se presenta una configuración experimental modular que puede ser adaptado a aplicaciones industriales, monitoreo en línea o sistemas de control de calidad. Se presentan mediciones en una muestra en base acuosa depositada sobre metal. Se muestran resultados en la medición de espesores, topografía de superficie y tomografía del materialItem Fabricación y Caracterización de Sustratos Plasmónicos Basados en Nanobastones de Oro(2015) Scarpettini, Alberto; Gutierrez, MarinaSe fabricaron sustratos plasmónicos mediante el recubrimiento controlado de superficies de vidrio y películas delgadas de oro con nanobastones de oro. Estos sustratos nanoestructurados poseen resonancias ópticas en el rango visible e infrarrojo cercano del espectro electromagnético, y producen grandes intensificaciones de campo, llamados puntos calientes, en regiones muy localizadas de su superficie. El control de estas propiedades ópticas y la posibilidad de sintonizar la respuesta espectral de un sustrato son fundamentales para el diseño y construcción de sensores moleculares ultrasensibles y de sondas de microscopía óptica de altísima resolución. Se sintetizaron nanobastones de oro utilizando métodos de crecimiento mediado por semillas, con un preciso control de sus dimensiones finales. Se obtuvieron suspensiones monodispersas y con alta eficiencia. Se modificaron químicamente superficies de vidrio y películas de oro para adsorber nanobastones de oro. Se controló la densidad de recubrimiento superficial mediante el tiempo de inmersión de los sustratos en la solución coloidal. Se caracterizaron los sustratos fabricados mediante espectros de extinción e imágenes de microscopía electrónica. Se obtuvieron recubrimientos homogéneos con bandas de absorción dadas por el acoplamiento de las resonancias de los nanobastones con el material del sustrato.Item Harmonic demodulation and minimum enhancement factors in field-enhanced near-field optical microscopy(2015-01) Scarpettini, Alberto; Bragas, Andrea VeronicaField enhanced scanning optical microscopy (FESOM) relies on the design and fabrication of plasmonic probes which had to provide optical and chemical contrast at the nanoscale. In order to do so, the scattering containing the near field information recorded in a FESOM experiment, has to surpass the background light, always present due multiple interferences between the macroscopic probe and sample. In this work, we show that when the probe-sample distance is modulated with very low amplitude, the higher the harmonic demodulation is, the better the ratio between the near field signal and the interferometric background results. The choice of working at a given n harmonic is dictated by the experiment when the signal at the n+1 harmonic goes below the experimental noise. We demonstrate that the optical contrast comes from the nth-derivative of the near field scattering, amplified by the interferometric background. By modeling the far and near field we calculate the probe-sample approach curves, which fit very well the experimental ones. After taking a great amount of experimental data for different probes and samples, we conclude with a table of the minimum enhancement factors needed to have optical contrast with FESOM.Item Recubrimiento controlado de sustratos de vidrio con nanobastones metálicos(2015-03-12) Gutierrez, Marina; Paredes, María Yanela; Scarpettini, AlbertoSe realizó la síntesis de nanobastones de oro monodispersos con una eficiencia superior al 80% sobre el total de nanopartículas, caracterizado por una resonancia plasmónica longitudinal cercana a los 800 nm. Se modi- ficaron superficialmente sustratos de vidrio y se los recubrió con los nanobastones sintetizados, con control de la densidad superficial. Se monitoreó la dinámica del recubrimiento a través de espectros de extinción, y se observó una densidad máxima de saturación dada por repulsión electrostática y un tiempo característico del proceso. Luego de alcanzada la saturación de nanobastones por unidad de área se observa un ensancha- miento de las resonancias hacia el infrarrojo, debido a interacciones entre los nanobastones por producirse agregaciones sobre la superficie. Estos resultados tienen aplicación inmediata en el diseño y fabricación de dispositivos plasmónicos, por ejemplo en el sensado molecular.Item Dynamic Detection of Thicknesses in Polymer Deformation Based on the Optical Coherence Interferometry Technique(2015-07-31) Morel, Eneas Nicolás; Torga, Jorge RománWe describe the implementation of the optical coherence interferometry (OCT) technique in the dynamic measurement of the deformation of polymers. The experimental set-up of the interferometer system and the signal processing used are also described. Theories and methods for measuring polymer film thickness are presented and the results are shown. In this work, the technique does not account for the determination of the refractive index.The study found that the dynamic estimation of the thickness of thin polymer films is possible and very accurateItem Dual system increases the resolution of a low coherence interferometer system through a signal detector astigmatic focus(2015-10-29) Morel, Eneas Nicolás; Aguilar, Andres; Torga, Jorge RománThe low coherence interferometry in Fourier space (FD-OCT) is a technique to measure distance with typical values of dynamic range in the order of 3 mm and resolution below 10 microns. In this paper we propose to combine the interferometric technique with a technique that measures distances using astigmatic focus signal, allowing lead the resolution limit of less than 10 nm. The experimental scheme shown armed with both techniques and experimental results in displacement of a sample surface, controlled feedback system with a piezoelectric strain gauge which we have used as a reference system..Item Dual system increases the resolution of a low coherence interferometer system through a signal detector astigmatic focus(2015-10-29) Morel, Eneas Nicolás; Aguilar, Andres; Torga, Jorge RománLa interferometría de baja coherencia en el espacio de Fourier (OCT-FD) es una técnica que permite medir distancia con valores típicos de rango dinámico en el orden de 3 mm y resolución por debajo de los 10 µm. En este trabajo se propone combinar esta técnica interferométrica con una técnica que mide distancias utilizando la señal de foco astigmática, lo que permite llevar el límite de resolución a menos de 10 nm. Se muestra el esquema experimental armado con ambas técnicas y resultados experimentales en desplazamientos de una superficie muestra, controlada con un sistema piezoeléctrico realimentado con strain-gauge que hemos utilizado como sistema de referenciaItem Interferometric system based on swept source-optical coherence tomography scheme applied to the measurement of distances of industrial interest(2015-12-11) Morel, Eneas Nicolás; Russo, Nélida A.; Torga, Jorge Román; Duchowicz, RicardoWe used an interferometric technique based on typical optical coherence tomography (OCT) schemes for measuring distances of industrial interest. The system employed as a light source a tunable erbium-doped fiber laser of ∼20-pm bandwidth with a tuning range between 1520 and 1570 nm. It has a sufficiently long coherence length to enable long depth range imaging. A set of fiber Bragg gratings was used as a self-calibration method, which has the advantage of being a passive system that requires no additional electronic devices. The proposed configuration and the coherence length of the laser enlarge the range of máximum distances that can be measured with the common OCT configuration, maintaining a good axial resolution. A measuring range slightly >17 cm was d0.etermined. The system performance was evaluated by studying the repeatability and axial resolution of the results when the same optical path difference was measured. Additionally, the thickness of a semitransparent medium was also measured.
- «
- 1 (current)
- 2
- 3
- »