Person: González Cano, Agustín
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Now showing 1 - 10 of 51
PublicationSelectivity of SPR fiber sensors in absorptive media: An experimental evaluation(Elsevier Science S A, 2011-12-15) Navarrete Fernández, María Cruz; Díaz Herrera, Natalia; González Cano, Agustín; Esteban Martínez, Óscar; Leite, IvoConventional surface plasmon resonance (SPR) fiber sensors show selective behavior when resonance wavelengths are tuned to absorption peaks of the surrounding medium, as it is experimentally shown and evaluated in this paper by using a doubly-deposited uniform-waist tapered optical fiber (DLUWT) and a dye as a test material. This behavior is clearly distinguishable from the usual response to nonabsorbing media and can be used to develop a new concept of SPR transducers. At the same time, the obtained results, which are in accordance with the theoretical predictions permit to increase the basic knowledge on surface plasma waves excitation in optical fibers. PublicationA fast method to measure the irradiance response of image processing systems(IOP Publishing Ltd., 1995-02) Quiroga Mellado, Juan Antonio; González Cano, Agustín; Bernabeu Martínez, EusebioA method to estimate in a fast and simple way the response of an image acquiring system (such as a charge-coupled device camera plus an image-processing board) for a monochromatic light source is presented. Two images, whose irradiances are related in a known way, are acquired, and the corresponding grey levels of the responses of the system are correlated pixel to pixel. From this correlation and the relationship between the irradiances of the images, a relative estimation of the irradiance response of the system can be obtained by means of simple algorithms. This method is fast and easy to implement and the results obtained are satisfactory. PublicationSimple model of compound waveguide structures used as fiber-optic sensors(Elsevier Sci. Ltd., 2000-03) Esteban Martínez, Óscar; Navarrete Fernández, María Cruz; González Cano, Agustín; Bernabeu Martínez, EusebioIn this work we present an application of a simple quasi-geometrical model to analyze the behavior of compound waveguide structures used as fiber-optic sensors. This theoretical model is based on the adjustment of the parameters of the structure from the experimental measures to predict the observed behavior of the device. It also takes into account the non-monocromaticity of the used source. In this way, it can be used as a design criterion for this kind of structures. It is applied to a refractive index fiber-optic sensor based on the excitation of surface plasmon in a metal layer by the light guided by a monomode fiber. PublicationMiniature Fiber Bragg Grating Strain Rosette Based on Lossless Tapers(Society of Photo-Optical Instrumentation Engineers (SPIE), 2011) Viegas, Diana Catarino das Neves; Navarrete Fernández, María Cruz; Díaz Herrera, Natalia; González Cano, Agustín; Santos , Jose Luis; Araújo, Fernanda MendesA miniature fiber Bragg grating strain rosette is presented. The proposed design is made possible through the development of low curvature radius lossless tapers, thus offering advantages in miniaturization of the rosette configuration. We report on the experimental validation of the miniature rosette design, demonstrating its effective operation. PublicationIn situ salinity measurements in seawater with a fibre-optic probe(IOP Publishing Ltd., 2006-08) Díaz Herrera, Natalia; Esteban Martínez, Óscar; Navarrete Fernández, María Cruz; Le Haitre, Michel; González Cano, AgustínWe have successfully proved the feasibility of an optical salinity meter for marine applications in a two-week measurement campaign, carried out for the realization of in situ salinity measurements in seawater. An optical instrument (optode), in which the main element is a fibre-optic refractive-index sensor based on surface plasmon resonance (SPR), has been developed for that purpose, and has been especially designed to be able to operate in realistic conditions. The performance of the optode has been evaluated on an oceanographic ship in the Baltic Sea, close to the Vistula estuarine area. The obtained results (in different tests, such as depth-profiling, towing and stationary measurements) show good correlation with the data provided by a commercial probe. Although the device is currently a part of a more complex measuring platform and uses an axial spectrograph as detector, the output power measurement used and the simplicity of its conception allow us to conceive a closed, extremely compact set-up which can be in principle commercially competitive with existing sensors. PublicationSeparation of isoclinics and isochromatics from photoelastic data with a regularized phase-tracking technique(The Optical Society of America, 2000-06-10) Quiroga Mellado, Juan Antonio; González Cano, AgustínWe present the application of a regularization algorithm to the processing of photoelastic fringe patterns. The method used is a modified regularized phase-tracking (RPT) algorithm applied to phase-shifted images. In particular, we present an algorithm for isoclinic-isochromatic separation that uses only five images. In the case of isoclinics the method can deal with problems associated with modulation of isochromatics and with isotropic points by means of a modified cost functional. With respect to the isochromatics the problems associated with regions of high fringe density are solved in a robust way by the unmodified RPT algorithm by use of the modulation information. The performance of the method is discussed, and experimental results are presented. PublicationFiber-optic salinity probe(Society of Photo-Optical Instrumentation Engineers (SPIE), 2004) Díaz Herrera, Natalia; Esteban Martínez, Óscar; Navarrete Fernández, María Cruz; González Cano, AgustínAn optical-fiber salinometer has been evaluated during a two-week measurement campaign in the Baltic Sea. The obtained results in three different tests are presented in comparison with those obtained with a standard electric CTD sonde commercially available. PublicationAn experimental evaluation of the behavior of SPR fiber sensors in absorptive medium when plasmons are tuned to absorption peak: method for selective measurement(Society of Photo-Optical Instrumentation Engineers (SPIE), 2011) Leite, I.; Navarrete Fernández, María Cruz; Díaz Herrera, Natalia; González Cano, Agustín; Esteban Martínez, ÓscarIn this work we present experimental results that confirm the influence of an absorptive surrounding medium in the behavior of conventional SPR fiber sensors. It can be observed that when a plasmon resonance coincides with a wavelength absorbed by the medium, the depth of the dip is affected, as predicted in the simulations. The results are important from the basic point of view, since the influence of absorptive medium in plasma waves has not been sufficiently studied up to date and they can also be used as the basis for a new method of SPR-based refractometry selective to specific analytes without the need of the addition of recognizing elements to the transducer. PublicationOn the dependence on isoclinics of the modulation of isochromatic phase maps(Gustav Fischer Verlag, 1999) Quiroga Mellado, Juan Antonio; González Cano, AgustínIn this work we evaluate the dependence on isoclinics of the modulation of the isochromatic phase maps when phase-shifting algorithms are applied to experiments of photoelasticity. This dependence makes conventional phase-shifting algorithms unsuitable for that application. PublicationA Polarization-Independent SPR Fiber Sensor(Springer Science+Business Media, 2010-03) Navarrete Fernández, María Cruz; Díaz Herrera, Natalia; González Cano, Agustín; Esteban Martínez, ÓscarThe resonance of surface plasma waves in metallic layers is a strongly polarization-dependent phenomenon by the very nature of the physical effect responsible of that resonance. This implies the necessity of polarization-controlling elements to be added to any operative surface-plasmon-resonance-based sensor. A fully symmetrical, circular-section double deposition of a metallic and a dielectric layer on a uniform-waist tapered optical fiber (SymDL-UWT) permits us to completely eliminate the dependence on polarization of the plasmon excitation, with the corresponding operative advantages and basic theoretical consequences. We depict the fabrication process of these transducers, which is based on the use of a simple and efficient rotating element developed by us, and show the characteristics of the produced devices. No such device has been depicted up to date. As our experimental results show, this kind of devices can be considered a very good option for the development of simple, compact, and efficient chemical and biological sensors.