Ana I. Gómez-Varela

Study of Different Sol-Gel Coatings to Enhance the Lifetime of PDMS Devices: Evaluation of Their Biocompatibility

A study of PDMS (polydimethylsiloxane) sol-gel–coated channels fabricated using soft lithography and a laser direct writing technique is presented. PDMS is a biocompatible material that presents a high versatility to reproduce several structures. It is widely employed in the fabrication of preclinical devices due to its advantages but it presents a rapid chemical deterioration to organic solvents. The use of sol-gel layers to cover the PDMS overcomes this problem since it provides the robustness of glass for the structures made with PDMS, decreasing its deterioration and changing the biocompatibility of the surface. In this work, PDMS channels are coated with three different kinds of sol-gel compositions (60MTES/40TEOS, 70MTES/30TISP and 80MTES/20TISP). The endothelial cell adhesion to the different coated devices is evaluated in order to determine the most suitable sol-gel preparation conditions to enhance cellular adhesion.

The USC-OSA-EPS section activities in optics

The USC-OSA Student Chapter and USC-EPS Young Minds Section is a group financed by The Optical Society (OSA) and the European Physical Society (EPS). It is formed by PhD and degree students from the Universidade de Santiago de Compostela (USC) and one supervisor of the Faculty of Physics. Its main goal is to promote and diffuse Optics in the society. For this purpose, the group carries out several activities in the academic and non-academic community. The group is also committed to the professional development of our members and motivates the exposition of our work into the scientific community.

Optics activity for hospitalized children

USC-OSA is a student chapter whose objective is to bring Optics knowledge closer to the non-optics community. The activity developed at the Hospital school was one of the most important last year. It was consisted in a few Optics experiments and workshops with hospitalized children of different ages and pathologies. The experiments had to be adapted to their physical conditions with the aim of everyone could participate. We think this activity has several benefits including spreading Optics through children meanwhile they have fun and forget their illness for a while.

A tolerance analysis on design parameters of parabolic and hyperbolic secant active GRIN materials for laser beam shaping purposes

The present paper considers two gain GRIN media, characterized by a complex parabolic and hyperbolic secant refractive index profile, for the design of uniform beam shaper systems. A general condition for beam shaping is obtained from the equation describing the evolution of the half-width of a plane Gaussian beam in the GRIN media. The simulation of the irradiance evolution of an input plane Gaussian beam—operating at 575 nm and beam waist radius of 0.45 mm—in each material is shown, in order to examine the beam shaping quality in terms of thickness of the active GRIN media and input beam wavelength.

The USC-OSA Student Chapter: goals and benefits for the optics community

The USC-OSA Student Chapter has been constituted in March 2013 by members of the University of Santiago de Compostela (USC) in Spain and sponsored by The Optical Society of America (OSA). It is formed by five graduate and one undergraduate students with the common interest in Optics and Photonics research and a professor of the USC is also involved as a faculty advisor. We decide to start this group with the aim to involve kids, precollege and undergraduate students in the world of Optics and Photonics. The activities that the USC-OSA Student Chapter members intend to realize are mainly educational tasks for the spreading of knowledge in Photonics by means of basic experiments, demonstrations and lectures by leading researches and teachers. Most of the needed resources to accomplish these activities are provided by the OSA, such as educational posters and a portable kit for demonstrating Optics to students. At this moment the USC-OSA Student Chapter is carrying out several activities, as educational journeys at the Santiago de Compostela University Hospital Complex (CHUS), where hospitalized children can approach to Optics through some simple experiments and games.. A teaching program is also being organized in collaboration with Galician secondary schools in order to show students the importance and uses of Optics and Photonics and to arouse their interest in this field, as well as encouraging them to develop their scientific thinking. Another activity will take place in November during the Science Week, which includes a program of lectures targeted to undergraduate students and an exposition of several demonstrations

A teaching resource using the GUIDE environment: simplified model of the eye for secondary school students

Nowadays, new technologies have great influence on our lives and how we access to the information. The new generations have never known a world without them and make use of these new technologies in practically all facets of their day-to-day. Education systems have also evolved rapidly and frequently make use of learning strategies based on interactive tools. In this work we have created a graphical user interface with GUIDE, a development environment of MATLAB, to show, in a simple way, how the eye works. This interactive program is addressed to the first courses of secondary education and designed to introduce them to the basic concepts of the normal refractive condition of the eye and the most common refractive errors, as myopia and hyperopia. The graphic interface makes use of the simplified model of the eye, where the optic system of the visual organ is represented by a converging lens (cornea and crystalline) and a screen (retina). Emmetropic, myopic and hyperopic eye operation is shown graphically to the students, as well as how these focusing errors can be solved with a diverging and converging lens, respectively. This teaching tool was used this academic course in the Colegio Hogar de Santa Margarita (A Coruna) for a better understanding of the students in this matter and to catch their attention to the world of Optics and its importance.

MATLAB GUI (Graphical User Interface) for the design of GRIN components for optical systems as an educational tool

New technologies and the available computing tools are becoming more important every day in the teaching evolution. The use of Graphical User Interfaces (GUI) with MATLAB enables the implementation of practical teaching methodologies to make easier the comprehension of a given subject. In this work, we report on the application of GUIs in order to provide the students with a simple tool for a better understanding on how to design GRIN elements for optical systems. Another GUIs advantage is that they can be converted to an executable file, so any student could use the interface in their own computer without having a MATLAB license. We present a graphical interface to show the performance of an optical device for controlling beam size and for deflecting light for coupling purposes, by a simple geometrical optics study, in a tapered GRIN lens illuminated by a parallel beam of tilted rays. We also show a graphical interface to obtain the maximum coupling efficiency between fundamental modes of two single-mode fibers by a scaling operation carried out by a GRIN fiber lens. With this interface the students can vary the magnification and the image plane in order to get the more suitable GRIN fiber lens to maximize the coupling efficiency between two fibers.

Design, performance, and tolerances of an active GRIN laser beam shaper

In this paper we present an active GRadient-INdex (GRIN) beam shaper with gain for Gaussian to flat-top beam conversion. This extra-cavity beam shaper is based in the proper design of an active GRIN selfoc rod microlens in order to perform the beam shaping operation. General condition for obtaining beam shaping by active GRIN rod microlenses is shown. Irradiance evolution through the active material for a laser beam operating at 1550 nm and 1.25 mm beam half-width is simulated and the shaping length in each case is determined. The active GRIN beam shaper is sensitive to deviations from design laser parameters such as wavelength and beam diameter, what can have great influence on the output flat-top beam quality. Variations on the design length of the shaper due to fabrication process errors can also emerge on unwanted output irradiance profiles. Here we analyze the sensitivity of the active GRIN beam shaper to the wavelength and beam half-width of the input Gaussian beam, as well as to the length of the GRIN rod lens in order to design a beam shaper that meets requirements within an acceptable tolerance. In this way, flatness quality of the output irradiance profile is examined. For the active beam shaper reported, microlens thickness, input wavelength and beam half-width tolerances are 10%, 10% and 5%, respectively.

Beam transformations by active selfoc microlenses

This work has been sponsored by Xunta de Galicia/Feder (INCITE08PXIB206013PR), Ministerio de Ciencia e Innovacion (MAT2010-18519) and CDTI (SURFALUX SOL-00030930), Spain. Besides, Ana I. Gomez-Varela wants to acknowledge the financial support from the FPU (Formacion de Profesorado Universitario) grant 2009 (Ministerio de Educacion, Spain).

Propagation of Gaussian Beams through Active GRIN Materials

We discussed light propagation through an active GRIN material that exhibits loss or gain. Effects of gain or loss in GRIN materials can be phenomenologically taken into account by using a complex refractive index in the wave equation. This work examines the implication of using a complex refractive index on light propagation in an active GRIN material illuminated by a non-uniform monochromatic wave described by a Gaussian beam. We analyze how a Gaussian beam is propagated through the active material in order to characterize it by the beam parameters and the transverse irradiance distribution.