Novel achromatic single reflection quarter-wave retarder: design and measurement

In this work, we present an achromatic quarter-wave retarder whose design is based upon the reflection properties of an isotropic-anisotropic interface. In theory, it is possible to obtain a π/2 phase shift by means of a total internal reflection at an isotropic-isotropic interface. However, in order to achieve such a phase shift, it is necessary to use a medium with a particularly high refractive index. We have previously shown that these phase shifts can be achieved by means of a total internal reflection in an isotropic-uniaxial interface, which allows the use of smaller refractive index media. By means of this property, we designed, built, and characterized a novel quarter-wave retarder that makes it possible to obtain circularly polarized light from a linear polarization state. We developed some guidelines that allowed us to obtain a device of competitive performance, low cost, and manageable manufacture.Fil: Veiras, Francisco Ezequiel. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Raffa, G.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Caré, D.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Perez, Liliana Ines. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garea, María Teresa. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentin

A birefringent polarization modulator: Application to phase measurement in conoscopic interference patterns

Conoscopic interferometry for crystal characterization is a very well known technique with increasing applications in different fields of technology. The advantage of the scheme proposed here is the introduction of a polarization modulator that allows the recovery of the phase information contained in conoscopic interferograms. This represents a real advantage since the most relevant physical information of the sample under study is usually contained in the phase of the fringe pattern. Moreover, this technique works successfully even when there are no visible fringes.The setup employed is a simple conoscopic interferometer where the elements under study correspond to two birefringent crystal slabs and a commercial mica wave plate. It allows the crystals to be characterized and the wave plate retardance to be measured as a function of the angle of incidence. The modulator itself consists of a single tiltable crystal plate which, by means of phase shifting techniques, permits the recovery of a phase map for each sample.  It is inexpensive and it can be easily calibrated, so it works with a wide range of phase shifting interferometry algorithms. We show that our scheme is easily adaptable to algorithms that require either a low or high amount of interferograms.Fil: Veiras, Francisco Ezequiel. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garea, María Teresa. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Perez, L. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentin

Effects of sevoflurane postconditioning on cell death, inflammation and TLR expression in human endothelial cells exposed to LPS

Background: Sevoflurane is an anesthetic agent which also participates in protective mechanisms in sepsis, likely due to anti-inflammatory properties. A key tissue in sepsis is the endothelium, which expresses TLR2 and TLR4 receptors, known regulators of inflammatory mechanisms and potential therapeutic targets for this pathology. In this context, we explored the effect of sevoflurane postconditioning in an in vitro sepsis model. Methods: Primary cultures of human umbilical vein endothelial cells were used for two different experiments. In the first set, cultures were placed in an airtight incubation chamber and exposed to different concentrations of sevoflurane (0,1,3 or 7% vol,) for 1 hour. In the second set, lipopolysaccharide from Escherichia coli 0111:B4 (1 μg/mL) was added to culture medium for 3 hours and cells were subsequently exposed to sevoflurane (0,1,3 or 7% vol,) for 1 hour as explained before. In both cases, cell viability was measured by MTT and Trypan blue assays, TLR2 and TLR4 expression were analyzed by flow cytometry, and TNFα and IL-6 levels were quantified in cell culture media by an immunoassay immediately after exposure, at 6 and 24 hours. Results: Exposure to 3% sevoflurane decreased TLR2 at 24 hours and TLR4 at 6 and 24 hours (both p<0.05), whereas exposure to 7% decreased TLR4 expression at 6 hours (p<0.05). Both 3 and 7% sevoflurane decreased TNF-α and IL-6 levels at 24 hours (both p<0.05). In LPS-stimulated cultures, exposure to 3% sevoflurane was cytoprotective at 6 and 24 hours (p<0.05) compared with control, and decreased TLR2 and TLR4 expression at 24 hours (p<0.05); whereas 7% decreased TLR4 expression at 24 hours (p<0.05). Both 3% and 7% sevoflurane decreased TNF-α and IL-6 levels at 24 hours (both p<0.05). Conclusions: Postconditioning with the halogenated anesthetic agent sevoflurane after LPS stimulation shows a cytoprotective effect in an in vitro model, decreasing cell death and reducing TLR2 and TLR4 expression as well as levels of the inflammatory mediators TNF-α and IL-6 in human endothelial cells

Celdas en cuña para refractometría: criterios de selección de materiales y parámetros

This work presents the materials and parameters selection criteria of wedge cells for refractometry in the visible range. These cells consist of two right angle prisms facing each other, defining a wedge-shaped cavity where the sample is placed. The refractive index of the sample is determined from the deviation of a light beam that traverses the cell. This model for engineering purposes includes the cell geometry and the refractive indexes of the cell material and the sample. We perform the numerical calculation and ray tracing of the optical system. We also propose polinomial fitting functions in order to simplify the numerical treatment, and as a complement to the complete set of equations. These polynomials give the refractive index of the sample as an explicit function of the deviation angle. An analysis of the approximation errors is also given.Este trabajo presenta criterios de selección de materiales y parámetros de celdas en cuña para refractometría en el rango visible. Estas celdas consisten en dos prismas de ángulo recto enfrentados, que definen una cavidad con forma de cuña entre ellas, en la que se coloca la muestra cuyo índice de refracción se desea medir. Éste se determina a partir de la desviación de un haz luminoso que atraviesa la celda. Este modelo para fines de ingeniería tiene en cuenta la geometría de la celda y los índices de refracción del material de la celda y de la muestra. A partir de allí realizamos el cálculo numérico y trazado de rayos correspondiente al sistema óptico. También proponemos ajustes polinómicos para simplificar el tratamiento numérico, como complemento de las ecuaciones completas. Estos polinomios dan el índice de refracción de la muestra como una función explícita del ángulo de deflexión. Se incluye además el análisis de los errores de la aproximación

Eduardo Pondal. Rumores de los pinos. Gravado á fotoaugaforte

Proyecto de investigación desarrollado por José Fuentes Esteve en torno al fotoaguafuerte sobre cobre

Wideband Transimpedance Amplifiers for Optoelectronics: Applications to Dynamic Interferometry

Abstract—This paper describes the design and performance of transimpedance amplifiers (TIAs) for optoelectronic systems, optimized for optical dynamic interferometry. To perform the analysis of the amplifiers, we show some experimental schemes, where different topologies were used. We describe the relevance of each TIA implemented, mentioning guidelines and design considerations.Resumen— Este artículo describe el diseño y desempeño de amplificadores de transimpedancia (TIAs) para optoelectrónica, optimizados para su uso en aplicaciones de interferometría óptica dinámica. Para desarrollar el análisis de los amplificadores, mostramos algunos esquemas experimentales donde se utilizan distintas topologías. En cada esquema desarrollado, describiremos la relevancia de cada TIA, mencionando lineamientos y consideraciones de diseño.Este artículo describe el diseño y desempeño de amplificadores de transimpedancia (TIAs) para optoelectrónica, optimizados para su uso en aplicaciones de interferometría óptica dinámica. Para desarrollar el análisis de los amplificadores, mostramos algunos esquemas experimentales donde se utilizan distintas topologías. En cada esquema desarrollado, describiremos la relevancia de cada TIA, mencionando lineamientos y consideraciones de diseño

Amplificadores de Transimpedancia de Banda Ancha para Optoelectrónica: Aplicaciones a la Interferometría Dinámica

Abstract—This paper describes the design and performance of transimpedance amplifiers (TIAs) for optoelectronic systems, optimized for optical dynamic interferometry. To perform the analysis of the amplifiers, we show some experimental schemes, where different topologies were used. We describe the relevance of each TIA implemented, mentioning guidelines and design considerations.Resumen— Este artículo describe el diseño y desempeño de amplificadores de transimpedancia (TIAs) para optoelectrónica, optimizados para su uso en aplicaciones de interferometría óptica dinámica. Para desarrollar el análisis de los amplificadores, mostramos algunos esquemas experimentales donde se utilizan distintas topologías. En cada esquema desarrollado, describiremos la relevancia de cada TIA, mencionando lineamientos y consideraciones de diseño.Este artículo describe el diseño y desempeño de amplificadores de transimpedancia (TIAs) para optoelectrónica, optimizados para su uso en aplicaciones de interferometría óptica dinámica. Para desarrollar el análisis de los amplificadores, mostramos algunos esquemas experimentales donde se utilizan distintas topologías. En cada esquema desarrollado, describiremos la relevancia de cada TIA, mencionando lineamientos y consideraciones de diseño

Software Defined Optoelectronics: Space and Frequency Diversity in Heterodyne Interferometry

In this paper, a general architecture for the implementation of software-defined optoelectronic systems is described. This concept harnesses the flexibility of software-defined hardware to implement optoelectronic systems which can be configured to adapt to multiple high speed optical engineering applications. As an application example, a software-defined optical interferometer using a commercial software-defined radio platform is built. The system is tested by performing high speed optical detection of laser-induced photoacoustic signals in a concentrated dye solution. Using software modifications only, conventional single carrier and also multicarrier heterodyne techniques with space and frequency diversity are performed. The latter technique shows a noticeable performance improvement in single-shot interferometric measurements.Fil: Riobó, Lucas Matías. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; ArgentinaFil: Veiras, Francisco Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; ArgentinaFil: Garea, María Teresa. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sorichetti, Patricio Aníbal. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; Argentin

Wideband quad optical sensor for high-speed sub-nanometer interferometry

This paper describes the design and performance of a low-noise and high-speed optical sensor that provides two output signals in quadrature from the simultaneous detection of four phase-shifted interferograms. The sensor employs four high-speed photodiodes and high-speed, low-noise transimpedance amplifiers. The optical and electronic design was optimized for high-speed displacement measurement interferometry, over a broad range of operating frequencies. Compared to other experimental schemes, the sensor is simpler and of lower cost. The performance of the sensor is demonstrated by characterizing a piezoelectric transducer for ultrasonic applications. We measured displacements between 38 pm and 32 nm with 6% relative uncertainty, in the frequency range from 1 to 2 MHz.Fil: Riobó, Lucas Matías. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Veiras, Francisco Ezequiel. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sorichetti, Patricio Aníbal. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garea, María Teresa. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Design method of optical detection systems based on transimpedance amplifiers

Designing detection systems based on transimpedance amplifiers is a complex task because noise, frequency response, and stability are coupled constraints. This work presents a straightforward design method of detection systems based on transimpedance amplifiers. We take into account the objectives, scope of the design, and requirements and specifications, including the input signal levels. According to the small-signal model, the noise and stability are analyzed in detail. We present a systematic procedure to search for the acceptable values of the feedback network components based on these analyses. Then, we define a merit function to compare the performance of the acceptable combinations of feedback network components. For every acceptable combination, the function gives a quantitative measure of the degree of compliance for each design parameter: signal-to-noise ratio, highest operating frequency, and phase margin. As an example, we apply the method to optimize the design of an optical detection system using a PIN photodiode and a low-noise operational amplifier.Fil: Vázquez, Patricia María Elena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Veiras, Francisco Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Ciocci Brazzano, Ligia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Sorichetti, Patricio Aníbal. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentin