Grupo de Nanofotonica

Permanent URI for this collectionhttp://48.217.138.120/handle/20.500.12272/1241

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Start date: 2010End date: 2019

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Now showing 1 - 10 of 34
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    Kinetic and plasmonic properties of gold nanorods adsorbed on glass substrates
    (2019-10-24) Gutiérrez, Marina V.; Scarpettini, Alberto Franco
    Monodisperse gold nanorods with different sizes were synthesized and adsorbed on chemically modified glass substrates. Influence of surfactant molar concentration on nanorod adsorption was studied and the optimum range was determined. During substrate coverages we monitored the growth of longitudinal localized surface plasmon resonances at short times due to density increase of isolated nanorods and, at longer times, their subsequent decrease and a concurrent growth of coupling resonances owing to nanoparticle surface mobility and aggregation. Temporal evolution of amplitudes of resonance peaks in extinction spectra and nanorod counting statistics in electron micrographs were used to model both coverage and aggregation processes, as exponentiallike functions of time. Their characteristic times and saturation values were analyzed and related to kinetic parameters, nanorod dimensions and extinction coefficients. This work can be used as a predictive tool to prepare plasmonic substrates with desired optical resonances.
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    Síntesis de nanopartículas híbridas dieléctrico-metal y estudio de sus propiedades ópticas
    (2018) Paredes, María; Scarpettini, Alberto
    Se sintetizaron y estudiaron nanopartículas esféricas del tipo núcleo-cáscara de sílice y oro, con control de sus dimensiones. En una primera etapa se realizó la síntesis de esferas de SiO2 monodispersas de varios tamaños, seguido de la funcionalización de su superficie. Se prepararon semillas de oro de muy pocos nanómetros, que se adsorbieron sobre las esferas funcionalizadas. Se estudió la dinámica de crecimiento de una capa uniforme de oro sobre las nanoesferas de SiO2 decoradas. Se observó la coalescencia de los grupos adsorbidos en la superficie, y se comprobó que el agente reductor y las condiciones de reacción son esenciales para evitar la nucleación del metal fuera de la superficie del núcleo. La formación de una capa de oro cerrada nos permite obtener estructuras núcleo-cascara, con esferas dieléctricas y recubrimiento metálico, cuyas resonancias plasmónicas se correlacionan muy bien con la teoría de Mie.
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    Kinetic and plasmonic properties of gold nanorods adsorbed on glass substrates
    (2019-09-19) Gutierrez, Marina; Scarpettini, Alberto F
    Monodisperse gold nanorods with different sizes were synthesized and adsorbed on chemically modified glass substrates. Influence of surfactant molar concentration on nanorod adsorption was studied and the optimum range was determined. During substrate coverages we monitored the growth of longitudinal localized Surface plasmon resonances at short times due to density increase of isolated nanorods and, at longer times, their subsequent decrease and a concurrent growth of coupling resonances owing to nanoparticle surface mobility andaggregation. Temporal evolution of amplitudes of resonance peaks in extinction spectra and nanorod counting statistics in electron micrographs were used to model both coverage and aggregation processes, as exponential- like functions of time. Their characteristic times and saturation values were analyzed and related to kinetic parameters, nanorod dimensions and extinction coefficients. This work can be used as a predictive tool to prepare plasmonic substrates with desired optical resonances.
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    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 Román
    Este 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.
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    Improved spectral resolution in time-varying interferometry
    (2018-11) Antonacci, Julian; Morel, Eneas Nicolás; Torga, Jorge Román; Duchowicz, Ricardo; Arenas, Gustavo
    In this work, we present a procedure that allows increasing the resolution of dynamic length measurements made by spectral interferometry. The proposed scheme leads to obtaining a compact photonic instrument with the ability to measure distances, variations on positions and vibrations with a very high resolution. This measurement system includes a superluminescent source (SLED), a digital spectrometer and a Fizeau interferometer. Spectral data is processed by applying Fourier domain techniques previously applied in optical coherence tomography. The resolution of the spectral measurement system is determined by the spectrometer bandwidth and the light source employed. A signal is obtained by analysing the time evolution of a single pixel from the spectrometer CCD sensor, which is later analysed using time domain interferometry (TDI) techniques. This procedure works by detecting changes in the optical path below those that can be detected by spectral analysis. The original resolution obtained with the solely spectral techniques was 2.2 µm but was improved to 40 nm by complementary analysis of temporal signals.
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    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 Román
    In 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.
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    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, Ricardo
    We 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.
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    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 Román
    En 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.
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    Scanning optical coherence tomography applied to the characterization of surfaces and coatings
    (El Sevier, 2014) Cerrotta, Santiago; Morel, Eneas Nicolás; Torga, Jorge Román
    This 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.
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    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 Román
    The 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..