Heuristic modelling of laser written mid-infrared LiNbO_3 stressed-cladding waveguides

Mid-infrared lithium niobate cladding waveguides have great potential in low-loss on-chip non-linear optical instruments such as mid-infrared spectrometers and frequency converters, but their three-dimensional femtosecond-laser fabrication is currently not well understood due to the complex interplay between achievable depressed index values and the stress-optic refractive index changes arising as a function of both laser fabrication parameters, and cladding arrangement. Moreover, both the stress-field anisotropy and the asymmetric shape of low-index tracks yield highly birefringent waveguides not useful for most applications where controlling and manipulating the polarization state of a light beam is crucial. To achieve true high performance devices a fundamental understanding on how these waveguides behave and how they can be ultimately optimized is required. In this work we employ a heuristic modelling approach based on the use of standard optical characterization data along with standard computational numerical methods to obtain a satisfactory approximate solution to the problem of designing realistic laser-written circuit building-blocks, such as straight waveguides, bends and evanescent splitters. We infer basic waveguide design parameters such as the complex index of refraction of laser-written tracks at 3.68 µm mid-infrared wavelengths, as well as the cross-sectional stress-optic index maps, obtaining an overall waveguide simulation that closely matches the measured mid-infrared waveguide properties in terms of anisotropy, mode field distributions and propagation losses. We then explore experimentally feasible waveguide designs in the search of a single-mode low-loss behaviour for both ordinary and extraordinary polarizations. We evaluate the overall losses of s-bend components unveiling the expected radiation bend losses of this type of waveguides, and finally showcase a prototype design of a low-loss evanescent splitter. Developing a realistic waveguide model with which robust waveguide designs can be developed will be key for exploiting the potential of the technology.This work was supported by the Spanish MINECO under project MAT2013-47395-C4-4-R, TEC2014-55948-R and FIS2013-44174-P. Catalan Government 2014SGR1358. European Commission (ACP2-GA-2013-314335-JEDI ACE). F. D. acknowledges additional support 2010-ICREA-02 for excellence in research

Surface ablation of RbTiOPO4 by femtosecond laser

We report here the results obtained in surface ablation of RbTiOPO4 single crystals by femtosecond laser. We fabricated and characterized one-dimensional (1D) diffraction gratings with different lattice spacings of 15 and 20 μm, and with a sub-modulation of the period introduced in the later. The optical and electronic microscopy characterization and filling factor analysis of these diffraction gratings are reported. We also show that the roughness generated on the grooves by the ablation process can be improved by chemical etching.This work was partially funded by the European Commission under the Seventh Framework Program under Project Cleanspace FP7-SPACE-2010-1-GA-263044, supported by the Spanish Government under Projects PI09/90527, TEC2009-09551, AECID A/024560/09, FIS2009-09522, HOPE CSD2007-00007 and SAUUL CSD2007-00013 (Consolider-Ingenio 2010), by Catalan Government under Projects 2009SGR235 and 2009SGR549, by Junta de Castilla y León under Project GR27, and by the Research Center on Engineering of Materials and Systems (EMaS) of the URV. J.J.C. is supported by the Education and Science Ministry of Spain and European Social Fund under the Ramón y Cajal program, RYC2006-858. We also acknowledge support from the Centro de Laseres Pulsados, CLPU, Salamanca, Spain

The Walnuts and Healthy Aging study (WAHA): Protocol for a Nutritional Intervention Trial with Walnuts on Brain Aging

Introduction: An unwanted consequence of population aging is the growing number of elderly at risk of neurodegenerative disorders, including dementia and macular degeneration. As nutritional and behavioral changes can delay disease progression, we designed the Walnuts and Healthy Aging (WAHA) study, a two-center, randomized, 2-year clinical trial conducted in free-living, cognitively healthy elderly men and women. Our interest in exploring the role of walnuts in maintaining cognitive and retinal health is based on extensive evidence supporting their cardio-protective and vascular health effects, which are linked to bioactive components, such as n-3 fatty acids and polyphenols. Methods: The primary aim of WAHA is to examine the effects of ingesting walnuts daily for 2 years on cognitive function and retinal health, assessed with a battery of neuropsychological tests and optical coherence tomography, respectively. All participants followed their habitual diet, adding walnuts at 15% of energy (≈30-60 g/day) (walnut group) or abstaining from walnuts (control group). Secondary outcomes include changes in adiposity, blood pressure, and serum and urinary biomarkers in all participants and brain magnetic resonance imaging in a subset. Results: From May 2012 to May 2014, 708 participants (mean age 69 years, 68% women) were randomized. The study ended in May 2016 with a 90% retention rate. Discussion: The results of WAHA might provide high-level evidence of the benefit of regular walnut consumption in delaying the onset of age-related cognitive impairment and retinal pathology. The findings should translate into public health policy and sound recommendations to the general population

EINA360 2021

Aquesta publicació és un recull del treball realitzat pels estudiants i exestudiants d’EINA. Mitjançant una selecció de projectes, es mostra el rigor acadèmic i la capacitat d’anàlisi i experimentació que tenen els alumnes del Grau de Disseny i dels diferents Màsters i Postgraus d’EINA. Aquesta filosofia, que fomenta el potencial innovador del disseny i l’art, també es recull en la praxis professional que duen a terme els nostres alumni. Tots els projectes publicats són una síntesi de l’aprenentatge enriquidor, obert a diferents sistemes de pensament i llenguatges, amb què EINA treballa des de la seva fundació el 1967. Una metodologia en constant evolució a d’avançar-se a les necessitats i exigències de la nostra societat canviant, per poder donar resposta als nous reptes i fer realitat nous productes, nous serveis i noves experiències. En definitiva, aquesta publicació és el testimoni de la trajectòria de l’escola com a plataforma de cultura i coneixement de generacions de professionals del disseny i l’art que participen activament en el desenvolupament d’una societat més sostenible, ètica, reflexiva i compromesa.Esta publicación es una recopilación del trabajo realizado por los estudiantes y exestudiantes de EINA. Mediante una selección de proyectos se muestra el rigor académico y la capacidad de análisis y experimentación que tienen los alumnos del Grado de Diseño y de los diferentes Másters y Postgrados de EINA. Esta filosofía, que fomenta el potencial innovador del diseño y el arte, también se recoge en la praxis profesional que llevan a cabo nuestro alumni. Todos los proyectos publicados son una síntesis del aprendizaje enriquecedor, abierto a diferentes sistemas de pensamiento y lenguajes, con que EINA trabaja desde su fundación en 1967. Una metodología en constante evolución con el fin de adelantarse a las necesidades y exigencias de nuestra sociedad cambiante, para poder dar respuesta a los nuevos retos y hacer realidad nuevos productos, nuevos servicios y nuevas experiencias. En definitiva, esta publicación es el testimonio de la trayectoria de la escuela como plataforma de cultura y conocimiento de generaciones de profesionales del diseño y el arte que participan activamente en el desarrollo de una sociedad más sostenible, ética, reflexiva y comprometida.This publication is a collection of the work of EINA’s students past and present, a selection of projects from the Degree in Design and the various Masters’ and Postgraduate programmes, chosen for their academic rigor and analytic and experimental capacity. This foundation, which fosters the innovative potential of design and art, is also reflected in the professional practice of our alumni. All of the published projects are a synthesis of the enriching learning style, open to different systems of thought and language, which EINA has prioritized since its founding in 1967. It is a methodology in constant evolution, whose aim is to advance to meet the needs and demands of our changing society, so as to be able to respond to new challenges and make new products, new services and new experiences a reality. In short, this publication is witness to the trajectory of the school as the platform for knowledge and culture behind generations of art and design professionals who actively participate in the development of a more sustainable, ethical, thoughtful and committed society

Thermal and Optical Characterization of Undoped and Neodymium-Doped Y3ScAl4O12 Ceramics

Y3–3xNd3xSc1Al4O12 (x = 0, 0.01, and 0.02) ceramics were fabricated by sintering at high temperature under vacuum. Unit cell parameter refinement and chemical analysis have been performed. The morphological characterization shows micrograins with no visible defects. The thermal analysis of these ceramics is presented, by measuring the specific heat in the temperature range from 300 to 500 K. Their values at room temperature are in the range 0.81–0.90 J g1–K–1. The thermal conductivity has been determined by two methods: by the experimental measurement of the thermal diffusivity by the photopyroelectric method, and by spectroscopy, evaluating the thermal load. The thermal conductivities are in the range 9.7–6.5 W K–1 m–1 in the temperature interval from 300 to 500 K. The thermooptic coefficients were measured at 632 nm by the dark mode method using a prism coupler, and the obtained values are in the range 12.8–13.3 × 10–6 K–1. The nonlinear refractive index values at 795 nm have been evaluated to calibrate the nonlinear optical response of these materials.This work is supported by the Spanish Government under projects MAT2011-29255-C02-01-02, MAT2013-47395-C4-4-R, and the Catalan Government under project 2014SGR1358. It was also funded by the European Commission under the Seventh Framework Programme, project Cleanspace, FP7-SPACE-2010-1-GA No. 263044

Single crystal growth, optical absorption and luminescence properties under VUV-UV synchrotron excitation of type III Ce3+^{3+}:KGd(PO3_3)4_4, a promising scintillator material

International audienceScintillator materials have gained great interest for many applications, among which the medical applications stand out. Nowadays, the research is focused on finding new scintillator materials with properties that suit the needs of each application. In particular, for medical diagnosis a fast and intense response under high-energy radiation excitation is of great importance. Here, type III Ce$^{3+}$:KGd(PO$_3$)$_4$ single crystals with high crystalline quality are grown and optically characterized as a new promising scintillator material. The $4f→5d$ electronic transitions of Ce$^{3+}$ are identified by optical absorption. The optical absorption cross section of Ce$^{3+}$ for the electronic transition from the $^2$F$_{5/2}$ to the $5d_1$ level is 370 × 10$^{−20}$ cm$^2$. The luminescence of KGd$_{0.996}$ Ce$_{0.004}$ (PO$_3$)$_4$ crystal by exciting the $5d$ levels of Ce$^{3+}$ with VUV-UV synchrotron radiation shows down-shifting properties with strong emissions at 322 and 342 nm from the $5d_1$ to $^2$F$_{5/2}$ and $^2$F$_{7/2}$ levels of Ce$^{3+}$ with a short decay time of ~16 ns, which is very suitable for scintillator applications. Moreover, these intense emissions are also observed when Gd$^{3+}$ is excited since an energy transfer from Gd$^{3+}$ to Ce$^{3+}$ exists