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Optical coherence tomography (OCT) has revolutionized ophthalmology over the past two decades. Comparable success in other medical and non-medical fields is still prevented by the high cost of OCT. Despite the benefit of OCT for other applications like dermatology, dentistry, and many industrial applications has been demonstrated, a poor cost/performance ratio compared to existing technologies is hindering its commercial success in these areas. The main cost driver of swept source OCT (SS-OCT) devices is the laser. We have identified a light source commonly used in telecom and consumer applications, which costs several magnitudes less than conventional swept sources and thereby enables low cost SS-OCT devices. We have developed a prototype of a SS-OCT system using this low cost source and MEMS scanners.

Resolved, 2021/2022

We show that anisotropic planar anti-guiding waveguide structures with two radiation channels toward the surrounding cladding materials can support unidirectional guided resonances (UGRs), where radiation is canceled in one of the radiation channels and redirected into the other. Their formation is subtle as it requires breaking the so-called polar anisotropy-symmetry of the structures. Then, UGRs appear at specific wavelengths and light propagation directions, are robust, and are characterized by phase singularities in the channel in which radiation is canceled. The mechanism we describe allows for ready selection of the radiation direction, as well as tuning of the wavelength and the propagation angle at which UGRs occur., H2020 Marie Sklodowska-Curie Action GA665884; Government of Spain (grants PGC2018-097035-B-I00; Severo Ochoa CEX2019-000910-S); Fundació Cellex; Fundació Mir-Puig; Generalitat de Catalunya (CERCA and AGAUR 2017-SGR-1400)., Peer Reviewed, Postprint (author's final draft)

Resolved

Bound states in the continuum (BICs) are modes that remain radiationless though they exist in the part of the spectrum that corresponds to radiating waves. They are a general wave phenomenon and following initial theoretical predictions and subsequent landmark experimental demonstrations of the existence of BICs in photonic systems, there has been an explosion of interest in photonic BICs. Planar anisotropic waveguides containing uniaxial materials support the existence of full vector BICs. In this thesis we study the properties of these full vector BICs using the leaky mode formalism. We start by studying a structure with an isotropic cover, a uniaxial core/film and a uniaxial substrate, where one of the basis waves in the substrate provides the radiation channel. We find that the orientation of the optic axes of the two materials has substantial impact on BIC existence. This allows us to define regimes of anisotropy-symmetry based on the orientation of the optic axes relative to the direction of propagation and the interface plane. Varying the offset between the film and substrate optic axes in the interface plane, or azimuthal anisotropy-symmetry breaking, leads to the distortion of the BIC lines of existence on the leaky mode. Moving either optic axis out of the interface plane, or polar anisotropy-symmetry breaking, leads to the BIC lines of existence collapsing to points. The collapse of the BIC lines of existence to discrete points when polar anisotropy-symmetry is broken also leads to a transformation from lines of phase discontinuity to phase singularities in the radiation channel amplitude which can be assigned winding numbers. The BICs are robust and cease to exist only when two BICs with opposite winding numbers merge in the parameter space or the BIC moves beyond the leaky mode cutoff. We also study the impact of the variation of the constitutive parameters of this waveguide on the existence of BICs. We find that varying the refractive indices of the di, Los estados ligados en el continuo (BIC) son modos que permanecen sin radiación aunque existen en la parte del espectro que corresponde a las ondas radiantes. Son un fenómeno ondulatorio general y, tras las predicciones teóricas iniciales y las demostraciones experimentales históricas posteriores de la existencia de BIC en sistemas fotónicos, ha habido una explosión de interés en los BIC fotónicos. Las guías de ondas planas anisotrópicas que contienen materiales uniaxiales respaldan la existencia de los BIC. En esta tesis estudiamos las propiedades de estos BIC utilizando el formalismo de modo con fugas. Comenzamos estudiando una estructura con una cubierta isotrópica, un núcleo / capa uniaxial y un sustrato uniaxial, donde una de las ondas base en el sustrato proporciona el canal de radiación. Encontramos que la orientación de los ejes ópticos de los dos materiales tiene un impacto sustancial en la existencia de BIC. Esto nos permite definir regímenes de anisotropía-simetría basados en la orientación de los ejes ópticos en relación con la dirección de propagación y el plano de interfaz. La variación del desplazamiento entre los ejes ópticos de la capa y el sustrato en el plano de la interfaz, o la ruptura de la simetría de anisotropía azimutal, conduce a la distorsión de las líneas de existencia BIC en el modo con fugas. Mover el eje óptico fuera del plano de la interfaz, o la ruptura de la simetría de anisotropía polar, lleva a que las líneas de existencia de los BIC colapsen en puntos. El colapso de las líneas de existencia BIC a puntos discretos también conduce a una transformación de líneas de discontinuidad de fase a singularidades de fase en la amplitud del canal de radiación a las que se les pueden asignar números de devanado. Los BIC son robustos y dejan de existir solo cuando dos BIC con números de devanados opuestos se fusionan en el espacio de parámetros o el BIC se mueve más allá del corte del modo de fugas. También estudiamos el impacto de la variación, Postprint (published version)

Resolved

We show that slow light in hyperbolic waveguides is linked to topological transitions in the dispersion diagram as the film thickness changes. The effect appears in symmetric planar structures with type II films, whose optical axis (OA) lies parallel to the waveguide interfaces. The transitions are mediated by elliptical mode branches that coalesce along the OA with anomalously ordered hyperbolic mode branches, resulting in a saddle point. When the thickness of the film increases further, the merged branch starts a transition to hyperbolic normally ordered modes propagating orthogonally to the OA. In this process, the saddle point transforms into a branch point featuring slow light for a broad range of thicknesses, and a new branch of ghost waves appears., Agència de Gestió d’Ajuts Universitaris i de Recerca (2017-SGR-1400); Ministerio de Economía y Competitividad (PGC2018-097035-B-I00, SEV-2015-0522); H2020 Marie Sklodowska-Curie Actions (GA665884); Fundación Cellex; Fundació Mir-Puig. National Science Foundation with a CAREER Grant No. ECCS-1749177., Award-winning, Postprint (author's final draft)

Bound states in the continuum (BICs) exist in a variety of physical systems where they appear as lossless propagating states surrounded by radiating modes. However, in the case of open systems, they coexist with continuous families of guided states, which may be modes or other BICs, located in different regions of the frequency-momentum parameter space. Here we report that waveguiding structures comprising anisotropic materials with two radiation channels where continuous families of modes are not possible whatsoever can support discrete BICs that exist for a single frequency and a single propagation direction. The results are isolated spectrally-discrete BIC states existing as lossless needles emerging from a sea of radiating leaky modes., H2020 Marie Sk lodowska-Curie Action GA665884; Government of Spain (grants PGC2018- 097035-B-I00; Severo Ochoa CEX2019-000910-S); Fundaci ´o Cellex; Fundaci´o Mir-Puig; Generalitat de Catalunya (CERCA and AGAUR 2017-SGR-1400)., Postprint (published version)

Resolved

Light-sheet fluorescence microscopy (LSFM) has proven to be a very useful technique at imaging living samples due to its low radiation doses and image acquisition speed. The light-sheet is usually produced by laser illumination but recent investigation has improved this technique by generating this laminar excitation utilizing an extended source and a photonic lantern (PL). By eliminating the temporal coherence that lasers provide, different interference phenomena such as speckles or striation are removed from the obtained images, apart from reducing the global cost. In this project we present a simulated analysis of this techniques in order to improve its design and give a wider understanding of its performance. The basic principles of LSFM design are explained, concerning both excitation and detection paths, to introduce a realistic LSFM illumination system supported, analyzed and improved by different realistic simulations. Then, the PL device is presented as a novel technique to produce light-sheet together with and extended source such as LEDs. The output of a photonic lantern made of 7 optical fibers has been simulated and introduced to the set-up to characterize the resulting light-sheet. We also present the simulations of different realistic PL imperfections that can occur due to its fabrication procedure, or set-up errors. The obtained illuminations are analyzed in each case to appreciate and evaluate its effects. Finally, a variation of the PL morphology is proposed to improve the uniformity of the illumination sheet., Light-sheet fluorescence microscopy (LSFM) ha demostrado ser una técnica muy útil para obtener imágenes de muestras vivas debido a sus bajas dosis de radiación y la velocidad de adquisición de imágenes. La lámina de luz generalmente se produce mediante iluminación láser, pero una investigación reciente ha mejorado esta técnica al generar esta excitación laminar utilizando una fuente extendida y una photonic lantern (PL). Al eliminar la coherencia temporal que proporcionan los láseres, se eliminan diferentes fenómenos de interferencia, como manchas o estrías, de las imágenes obtenidas, además de reducir el coste global. En este proyecto presentamos un análisis simulado de estas técnicas para mejorar su diseño y dar una comprensión más amplia de su rendimiento. Se explican los principios básicos del diseño de LSFM, tanto en lo que respecta a la rama de excitación como la de detección, para introducir un sistema de iluminación realista de LSFM analizado y optimizado por diferentes simulaciones realistas. Luego, el dispositivo de PL se presenta como una técnica novedosa para producir láminas de luz junto con una fuente extendida como un LED. La salida de una PL hecha de 7 fibras ópticas se ha simulado e introducido en la configuración para caracterizar la lámina de luz resultante. También presentamos las simulaciones de diferentes imperfecciones realistas de la PL que pueden ocurrir debido a su procedimiento de fabricación o errores de alineación. Las iluminaciones obtenidas se analizan en cada caso para apreciar y evaluar sus efectos. Finalmente, se propone una variación de la morfología PL para mejorar la uniformidad de la lámina de iluminación., Light-sheet fluorescence microscopy (LSFM) ha demostrat ser una tècnica molt útil per obtenir imatges de mostres vives causa de les seves baixes dosis de radiació i la velocitat d'adquisició d'imatges. La làmina de llum generalment es produeix mitjançant il·luminació làser, però una investigació recent ha millorat aquesta tècnica al generar aquesta excitació laminar utilitzant una font estesa i una Photonic lantern (PL). A l'eliminar la coherència temporal que proporcionen els làsers, s'eliminen diferents fenòmens d'interferència, com taques o estries, de les imatges obtingudes, a més de reduir el cost global. En aquest projecte presentem una anàlisi simulat d'aquestes tècniques per millorar el seu disseny i donar una comprensió més àmplia del seu rendiment. S'expliquen els principis bàsics de el disseny de LSFM, tant pel que fa a la branca d'excitació com la de detecció, per introduir un sistema d'il·luminació realista de LSFM analitzat i optimitzat per diferents simulacions realistes. Després, el dispositiu de PL es presenta com una tècnica innovadora per produir làmines de llum juntament amb una font estesa com un LED. La sortida d'una PL feta de 7 fibres òptiques s'ha simulat i introduït en la configuració per caracteritzar la làmina de llum resultant. També es presenten les simulacions de diferents imperfeccions realistes de la PL que poden ocórrer a causa de la seva procediment de fabricació o errors d'alineació. Les il·luminacions obtingudes s'analitzen en cada cas per apreciar i avaluar-ne els efectes. Finalment, es proposa una variació de la morfologia PL per millorar la uniformitat de la làmina d'il·luminació.

Sepsis is a fatal disease that accounts for about 6 million deaths per year. Its diagnosis is extremely challenging and at the same time needs to be fast for effective intervention. Several protein biomarkers have been associated to sepsis and their detection is thus of paramount importance for fighting the disease and increase survival possibilities for pa- tients. These biomarkers are difficult to measure in relevant concentrations and in a rapid manner with currently available technologies. Over the last years, the Optoelectronics group at ICFO has been developing a lens-free interferometric microscope (LIM) that ffers suitable characteristics for point of care de- tection of sepsis. It is capable of detecting biomarkers at low concentration (below 500 ng/mL) without the use of uorescence labelling. Moreover, its large detection area allows multiplexing for simultaneous detection of several biomarkers. Most impor- tantly, preliminary experiments show that the LIM technology can potentially provide a fast resolving time, within 30 minutes, much shorter than that achievable with currently available techniques (tens of hours). Despite the initial promising results in pre-clinical studies, the limit of detection and time to result have large margin of improvement, espe- cially for some specific biomarkers (e.g. mRNA and PCT). The main aim of this thesis is to reduce the measurement duration by selecting only the area of interest among the images captured by the microscope's camera. Another goal is to implement a standard method to quantify the noise in such a way that the limit of detection can be derived and compared to other devices, following the guidelines described by ISO 25178 standards. This is a significant step toward the deployment and commercialization of the LIM technology, in the sepsis as well as other biomedical markets., Contribución al microscopio interferométrico sin lente desarrollado en el ICFO. La tesis consiste en la optimización del ruido implementando un área de interés, así como la caracterización del ruído de medida mediante métodos estandarizados por ISO 25178, Contribución al microscopio interferométrico sin lente desarrollado en el ICFO. La tesis consiste en la optimización del ruido implementando un área de interés, así como la caracterización del ruído de medida mediante métodos estandarizados por ISO 25178

Radiation of leaky modes existing in anisotropic waveguides can be cancelled by destructive interference at special propagation directions relative to the optical axis orientation, resulting in fully bound states surrounded by radiative modes. Here we study the variation of the loci of such special directions in terms of the waveguide constitutive parameters. We show that the angular loci of the bound states is sensitive to several design parameters, allowing bound states to exist for a broad range of angular directions and wavelengths and suggesting applications in filtering and sensing., Peer Reviewed, Postprint (author's final draft)

Bound states in the continuum (BICs), first predicted in the field of quantum physics [1], are localized radiationless states existing in the part of the spectrum that corresponds to radiative modes. BICs are a general wave phenomenon and have recently been found in photonic systems [2]. They are known to exist in photonic structures in almost-pure transverse-electric (TE) or transverse-magnetic (TM) states, at fixed frequencies and propagation directions [3]. More recently, we have shown the existence of fully hybrid BICs alongside pure TE/TM BICs in planar structures containing uniaxial materials in both symmetric and asymmetric geometries [4]. BICs occur when we decouple the radiation mode from the continuum by suppressing the radiation channel. This can happen in anisotropic planar structures due to polarization separation or destructive interference. The fact that interferometric BICs change propagation direction with frequency suggests that the structure gives itself to potential applications as spatial and spectral filters., Peer Reviewed, Postprint (published version)

We put forward the use of transformation optics to map surface waves that exist as one-dimensional modes supported by anisotropic structures into bound states in two-dimensional geometries. Specifically, we show the conformal mapping of Dyakonov waves existing in infinite planar surfaces separating birefringent media into bound modes supported by a cylindrical structure made of suitable metamaterials. In contrast with the original Dyakonov waves, the resulting fiber-like modes are highly dispersive, may exist as fundamental as well as higher-order states, feature helical wave fronts, and exhibit a lower and upper frequency cutoff. The program we put forward can be applied to all wave phenomena currently known to occur only in planar geometries in different types of anisotropic media., Peer Reviewed, Postprint (author's final draft)

Resolved

We uncover the existence of Dirac and exceptional points in waveguides made of anisotropic materials, and study the transition between them. Dirac points in the dispersion diagram appear at propagation directions where the matrix describing the eigenvalue problem for bound states splits into two blocks, sorting the eigenmodes either by polarization or by inner mode symmetry. Introducing a non-Hermitian channel via a suitable leakage mechanism causes the Dirac points to transform into exceptional points connected by a Fermi arc. The exceptional points arise as improper hybrid leaky states and, importantly, are found to occur always out of the anisotropy symmetry planes., Peer Reviewed, Postprint (published version)

Hyperbolic metamaterials (HMMs) are uniaxial materials that have hyperbolic dispersion curves. There are two types of hyperbolic metamaterials, type I that is described by a permittivity tensor with e|| < 0 and e¿ > 0, and type II that has e|| > 0 and e¿ < 0. Planar waveguides with hyperbolic materials have been mostly studied with propagation direction along the principal axis of the dielectric tensor only. Such studies showed that modes feature anomalous ordering in such a way that cut-off appears for lower order modes as light frequency increases. Interestingly, stopped light featuring null group velocity at specific wavelengths has been predicted for modes near cut-off in type II HMMs planar waveguides with optical axis (OA) oriented along the propagation direction [1]. Here, we theoretically study light propagation in type II HMMs planar waveguides for any orientation ¿ of the OA contained in a plane parallel to the waveguides interfaces. The results shows that a change in the wavelength only changes the OA direction ¿ at which stopped light exist. The process is a consequence of the lack of mode cut-off and it is caused by a mode spectroscopy transition from hyperbolic modes with anomalous order propagating along the OA (¿ = 0º), to modes with normal order, propagating orthogonally to the OA (¿ = 90º)., Peer Reviewed, Postprint (published version)

Precise clinical diagnosis of skin tumours relies on biopsy and subsequent histopathologic examination, an invasive method which represents a difficult task for clinicians to decide when to biopsy or not. For this reason, there is a significant demand for an automated, non-invasive, objective and fast method that could help clinicians to decide which is the most appropriate treatment. Concretely, the distinction of intermediate lesions is a clinical challenge since they are difficult to distinguish from malignant melanomas in terms of clinical, microscopical morphology, and genomic aspects. In addition, previous studies suggest that the concentration ratio of specific molecules is distinct between different classes of tumours. Then, studying the content of these molecules in skin tumours could lead to a better understanding of the chemical processes involved and to a suitable classification of them. In this study, Raman spectroscopy, together with multivariate statistical analysis, are proposed to classify skin tumours and to quantify the content of molecules related to skin cancer within them in a fast, label-free, objective and non-invasive way. In total, 66 skin tumour biopsies have been analysed with different malignancy grades. By means of multivariate analysis, skin tumours have been classified. The values of sensitivity and specificity of distinguishing malignant melanomas from intermediate lesions are 86.7% and 94.1%. Comparing with the accuracy of dermatologists, these results suggest that Raman spectroscopy is a promising fast, objective and non-invasive method able to enhance clinical diagnosis. In parallel, by means of another multivariate analysis method, the Raman spectral components and concentrations of specific molecules have been obtained from the different group of samples. Their differences in concentration may be indicative of an important role within the different development and aggressivity of skin lesions, and also may lead to an improved st, El diagnóstico clínico preciso de los tumores de la piel se basa en la biopsia y el posterior examen histopatológico, un método invasivo que representa una tarea difícil para los médicos decidir cuándo realizar una biopsia o no. Por este motivo, existe una importante demanda de un método automatizado, no invasivo, objetivo y rápido que pueda ayudar a los médicos a decidir cuál es el tratamiento más adecuado. Concretamente, la distinción de lesiones intermedias es un desafío clínico, ya que son difíciles de distinguir de los melanomas malignos en términos de morfología clínica, microscópica y aspectos genómicos. Además, estudios previos sugieren que la proporción de la concentración de moléculas específicas es distinta entre las diferentes clases de tumores. En consecuencia, el estudio del contenido de estas moléculas en los tumores de la piel podría llevar a una mejor comprensión de los procesos químicos involucrados y a una clasificación adecuada de ellos. En este estudio, se propone la espectroscopia Raman, junto con el análisis estadístico multivariante, para clasificar los tumores de la piel y cuantificar en ellos el contenido de las moléculas relacionadas con el cáncer de piel de una manera rápida, sin marcajes, objetiva y no invasiva. En total, se han analizado 66 biopsias de tumores de piel con diferentes grados de malignidad. Mediante análisis multivariante, se han clasificado los tumores cutáneos. Los valores de sensibilidad y especificidad de los melanomas malignos distinguidos frente las lesiones intermedias son 86.7% y 94.1%, respectivamente En comparación con la precisión de los dermatólogos, estos resultados sugieren que la espectroscopia Raman es un método prometedor, rápido, objetivo y no invasivo capaz de mejorar el diagnóstico clínico. Paralelamente, mediante otro método de análisis multivariante, los componentes espectrales Raman y las concentraciones de moléculas específicas se han obtenido de diferentes grupos de muestras. Sus diferencias en con, El diagnòstic clínic precís dels tumors de la pell es basa en la biòpsia i l'examen histopatològic posterior, un mètode invasiu que representa una tasca difícil per als clínics per decidir quan realitzar una biòpsia o no. Per aquest motiu, hi ha una demanda important per a un mètode automatitzat, no invasiu, objectiu i ràpid que pugui ajudar els clínics a decidir quin és el tractament més adequat. Concretament, la distinció de lesions intermèdies és un repte clínic, ja que són difícils de distingir de melanomes malignes en termes de morfologia clínica, microscòpica i genòmica. A més, estudis previs suggereixen que la proporció de concentració de molècules específiques és diferent entre diferents classes de tumors. En conseqüència, estudiar el contingut d'aquestes molècules en els tumors de la pell podria permetre una millor comprensió dels processos químics implicats i una classificació adequada dels mateixos. En aquest estudi, l'espectroscòpia Raman, juntament amb l'anàlisi estadística multivariant, es proposen per classificar els tumors de la pell i quantificar en ells el contingut de molècules relacionades amb el càncer de pell d'una manera ràpida, sense marcatges, objectiva i no invasiva. En total, s'han analitzat 66 biòpsies de tumors de la pell amb diferents graus de malignitat. Mitjançant l'anàlisi multivariant, s'han classificat els tumors de la pell. Els valors de sensibilitat i especificitat de distingir els melanomes malignes de les lesions intermèdies són 86,7% i 94,1%, respectivament. En comparació amb la precisió dels dermatòlegs, aquests resultats suggereixen que l'espectroscòpia Raman és un mètode ràpid, objectiu i no invasiu prometedor, capaç de millorar el diagnòstic clínic. Paral·lelament, mitjançant un altre mètode d'anàlisi multivariant, s'han obtingut els components espectrals Raman i les concentracions de molècules específiques dels diferents grups de mostres. Les seves diferències de concentració poden ser indicatives d'un paper important en

We demonstrate that Bound states In the Continuum (BICs) are supported in planar anisotropic structures where the optic axes are arbitrarily oriented. Moreover, we reveal fundamental new topological properties of these BICs that depend on the relative orientation of the optic axes in the core and substrate., Peer Reviewed, Postprint (published version)

Waveguiding structures made of anisotropic media support bound states in the continuum (BICs) that arise when the radiation channel of otherwise semileaky modes is suppressed. Hitherto, only structures with optical axes aligned in symmetric orientations inside the waveguide plane, where BICs appear as lines in the momentum-frequency dispersion diagram, have been considered. Here we address settings where such symmetry is broken and unveil a number of fundamental different features. Weak and strong symmetry-breaking regimes are identified, corresponding to azimuthal and polar optical axes orientation asymmetries, respectively. The azimuthal symmetry breaking is found to still preserve the existence loci of BICs in the momentum-frequency dispersion diagram as lines. However, all possible BICs become interferometric, while the polarization separable states that occur in symmetric settings cease to exist. The polar symmetry breaking has stronger effects and transforms the BICs’ existence loci from lines to points, which correspond to full-vector states that exist at discrete values of the optical axis orientation for a given wavelength. Such transformation results in fundamental changes in the topological properties of the radiated field around the BICs., Peer Reviewed, Postprint (published version)

We studied with the LugiatoLefever spatiotemporal formalism the existence, formation and dynamics of solitons in non-linear Kerr micro-resonators. For anomalous and normal dispersion we find different types of solitons, bright and dark respectively. We have determined the region of existence and stability for both types of structures and have studied the introduction of third order dispersion which gives a velocity to the solitons and stabilises them. In the normal GVD regime, we could not find the recently proposed flat top solitons. Ideas why this is the case are discussed.

Resolved

Due to relatively high powers used in STED, biological samples may be affected by the illumination in the process of image acquisition. Similarly, the performance of the system may be limited by the sample itself. Optimization of the STED parameters taking into account the sample itself is therefore a complex task as there is no clear methodology that can determine the image improvement in an objective and quantitative manner. In this work, a method based on Fourier transform formalism is presented to analyze the performance of a STED system. The spatial frequency distribution of pairs of confocal and STED images are compared to obtain an objective parameter, the Azimuth Averaged Spectral Content Spread (AASCS), that is related to the performance of the system in which the sample is also considered. The method has been first tested on samples of beads, and then applied to cell samples labeled with multiple fluorescent dyes. The results show that a single parameter, the AASCS, can be used to determine the optimal settings for STED image acquisition in an objective way, only by using the information provided by the images from the sample themselves. The AASCS also helps minimize the depletion power, for better preservation of the samples., Peer Reviewed, Postprint (published version)

En col·laboració amb la Universitat Autònoma de Barcelona (UAB), la Universitat de Barcelona (UB) i l’Institut de Ciències Fotòniques (ICFO)

The objective of this work has been to elucidate the structure of metal chelates such as Fe and Zn with amino acids. To achieve this objective crystals were obtained with glycine, by two methods: precipitation and evaporation; to which metallic cations (Fe2+ and Zn2+) were added at different pH. Once the crystals were obtained, they were analyzed by FTIR spectroscopy, to later perform an analysis of the spectra obtained. The conclusions reached were that, the crystals do not have the same structure if they are obtained by precipitation or by evaporation. It was also found that the water molecules of the crystal were not completely removed by the evaporation method. Coordination with glycine was different in each cation; the Fe2+ cation was coordinated with 3 glycines, while the Zn2+ cation was coordinated with 2 glycines., L'objectiu d'aquest treball ha estat elucidar sobre l'estructura dels quelats de metalls com el Fe i el Zn amb aminoàcids. Per aconseguir aquest objectiu es van obtenir cristalls amb glicina, mitjançant dos mètodes: precipitació i evaporació; als quals es van afegir cations metàl·lics (Fe2+ i Zn 2+) a diferents pH. Un cop obtinguts els cristalls, es van analitzar mitjançant espectroscòpia FTIR, per a posteriorment realitzar una anàlisi dels espectres obtinguts. Les conclusions a què es van arribar van ser que, els vidres no tenen la mateixa estructura si són obtinguts per precipitació o per evaporació. També es va comprovar que mitjançant el mètode d'evaporació no es van eliminar totalment les molècules d'aigua del vidre. La coordinació amb la glicina va ser diferent en cada catió; el catió Fe2+ es va coordinar amb 3 glicines, mentre que el catió Zn2+ es va coordinar amb 2 glicines., El objetivo de este trabajo ha sido elucidar sobre la estructura de los quelados de metales como el Fe y el Zn con aminoácidos. Para conseguir este objetivo se obtuvieron cristales con glicina, mediante dos métodos: precipitación y evaporación; a los que se añadieron cationes metálicos (Fe2+ y Zn2+) a diferentes pH. Una vez obtenidos los cristales, se analizaron mediante espectroscopía FTIR, para posteriormente realizar un análisis de los espectros obtenidos. Las conclusiones a las que se llegaron fueron que, los cristales no tienen la misma estructura si son obtenidos por precipitación o por evaporación. También se comprobó que mediante el método de evaporación no se eliminaron totalmente las moléculas de agua del cristal. La coordinación con la glicina fue diferente en cada catión; el catión Fe2+ se coordinó con 3 glicinas, mientras que el catión Zn2+ se coordinó con 2 glicinas.

The esterase enzyme is in dimer form but at specific conditions it changes its structure to monomer. A study is carried out on how the enzyme performs its highest enzymatic activity and therefore provides its optimum working temperature and denaturation temperature using UV-Vis absorption spectroscopy. It is intended to spectrophotometrically characterize the activity of porcine liver esterase., L'enzim esterasa està en forma de dímer però a unes condicions específiques canvia la seva estructura a monòmer. Es realitza un estudi sobre en quina forma l'enzim realitza la seva major activitat enzimàtica i per tant proporcionar la seva temperatura òptima de treball i la seva temperatura de desnaturalització utilitzant l'espectroscòpia d'absorció UV-Vis. Es pretén caracteritzar espectrofotomètricament l'activitat de l'esterasa de fetge porcina., La enzima esterasa está en forma de dímero pero a unas condiciones específicas cambia su estructura a monómero. Se realiza un estudio sobre en qué forma la enzima realiza su mayor actividad enzimática y por lo tanto proporcionar su temperatura óptima de trabajo y su temperatura de desnaturalización utilizando la espectroscopia de absorción UV-Vis. Se pretende caracterizar espectrofotométricamente la actividad de la esterasa de hígado porcina.

Imaging molecular structures separated by distances of a few nanometers still represents a complex challenge. Moreover, it is normally restricted to observations on thin (few micrometers) samples. In this work, we rotate the polarization of the excitation beam of two-photon excited fluorescence (TPEF) images to show that fluorescent structures at the molecular scale can be discriminated in a living organism. The polarization rotation generates a modulation of the signal intensity in each pixel of the TPEF images that carry information related to the fluorophore orientation. We analyze the signal modulation in every pixel of the polarization-resolved (PR) TPEF images through a Fourier analysis and generate images for the different Fourier components. Doing that, we show that two fluorophores oriented in different directions can be distinguished. Although by imaging the Fourier components the resolution of the optical system restricts the exact localization of two close molecules, discrimination is still possible even when the molecules are located at sub-diffraction distances. We propose a model that predicts this behavior, and demonstrate it experimentally in the neurons of a living Caenorhabditis elegans nematode, where we distinguish the walls of an axon with a diameter below the objective resolution. Since the technique is based in TPEF, the method can be extended to deep tissue imaging and has potential applications in single molecule detection, biological sensors, or super-resolution imaging techniques., Peer Reviewed, Postprint (published version)

Bound states in the continuum (BICs) are radiationless localized states embedded in the part of the parameter space that otherwise corresponds to radiative modes. Many decades after their original prediction1, 2, 3 and early observations in acoustic systems4, such states have been demonstrated recently in photonic structures with engineered geometries5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18. Here, we put forward a mechanism, based on waveguiding structures that contain anisotropic birefringent materials, that affords the existence of BICs with fundamentally new properties. In particular, anisotropy-induced BICs may exist in symmetric as well as in asymmetric geometries; they may form in tunable angular propagation directions; their polarization may be pure transverse electric, pure transverse magnetic or full vector with tunable polarization hybridity; and they may be the only possible bound states of properly designed structures, and thus appear as a discrete, isolated bound state embedded in a whole sea of radiative states., Peer Reviewed, Postprint (author's final draft)

Due to relatively high powers used in STED, biological samples may be affected by the illumination in the process of image acquisition. Similarly, the performance of the system may be limited by the sample itself. Optimization of the STED parameters taking into account the sample itself is therefore a complex task as there is no clear methodology that can determine the image improvement in an objective and quantitative manner. In this work, a method based on Fourier transform formalism is presented to analyze the performance of a STED system. The spatial frequency distribution of pairs of confocal and STED images are compared to obtain an objective parameter, the Azimuth Averaged Spectral Content Spread (AASCS), that is related to the performance of the system in which the sample is also considered. The method has been first tested on samples of beads, and then applied to cell samples labeled with multiple fluorescent dyes. The results show that a single parameter, the AASCS, can be used to determine the optimal settings for STED image acquisition in an objective way, only by using the information provided by the images from the sample themselves. The AASCS also helps minimize the depletion power, for better preservation of the samples., Peer Reviewed, Postprint (published version)

We report theoretical and experimental observation of radiationless bound states in the continuum (BIC) in waveguiding anisotropic structures. BICs may have all possible polarizations and be the only possible boundstates in the structure., Peer Reviewed, Postprint (published version)

Ultraviolet radiation has been successfully applied to the reduction of microorganisms on the surface of different foods, having the advantage that the sensory characteristics of said foods, like their taste, or their flavour, among others, are minimally affected. Likewise, it presents an ecologically friendly alternative, given that it doesn't contaminate the environment, and it doesn't generate compounds that could harm the health of consumers. However, related studies, which have applied this sort of technology, generally focus in the disinfection of several fruit juices, which must be relatively transparent, as the density of their consistency affects the disinfection process. Therefore, this project aims to offer an extensive review of previous work related with the application of the basic principles of ultraviolet radiation, specifically, in the disinfection of solid foods, as well as the potential generating sources of this type of light, with the purpose of contributing to the development of a possible standardisation of this disinfection technique. Additionally, a model of a prototype for a machine with the main purpose of disinfecting solid samples of food, which does not damage their respective properties, is proposed. This model will employ an automatised system for the reutilisation of pineapple samples, which are currently found at the School of Agriculture of Barcelona (ESAB)., La radiación ultravioleta se ha utilizado exitosamente para disminuir la cantidad de microorganismos en la superficie de distintos alimentos, al tener la ventaja de que las características sensoriales de dichos alimentos, como el olor, el sabor, o la textura entre otras, se ven mínimamente afectadas. Asimismo esta técnica de desinfección presenta una alternativa ecológicamente amigable, ya que no contamina el ambiente y además no genera compuestos dañinos para la salud del consumidor. No obstante, los estudios relacionados con la utilización de este tipo de técnica, generalmente se enfocan en la desinfección de distintos zumos de frutas, los cuales deben ser relativamente transparentes, ya que la densidad de su consistencia, afecta el proceso de purificación. Por lo tanto, este trabajo tiene la finalidad de recopilar los avances en la investigación relacionada con la aplicación de los principios básicos de la radiación ultravioleta, específicamente, en procesos de desinfección de alimentos sólidos, así como las potenciales fuentes de generación de este tipo de luz. Con el propósito de contribuir al desarrollo de una posible estandarización de esta técnica de desinfección de alimentos sólidos. Adicionalmente, se propone un modelo piloto de una máquina cuya función principal es la desinfección de muestras sólidas de alimentos sin dañar sus propiedades respectivas. Dicho modelo, empleará un sistema automatizado para la reutilización de muestras de piña, mismas que se encuentran actualmente en el laboratorio de la Escuela Superior de Agricultura de Barcelona (ESAB) de la Universidad Politécnica de Cataluña (UPC).

Investigación sobre spatial-division multiplexing (SDM) en comunicaciones por fibra óptica, In this work we analyze propagating LP modes (Linearly Polarized) in different independent spatial paths, mentioning the energetic density of the electromagnetic fields of these modes with a fixed normalized frequency and the evolution during the normalized frequency’s increment too. Thus, we have implemented an analytic and visual study through MATLAB programming language., En este trabajo analizaremos los modos de propagación LP (Linearly Polarized) en distintos caminos espaciales independientes, atendiendo a la densidad energética de los campos electromagnéticos de dichos modos con una frecuencia normalizada fijada y también a su evolución a medida que ésta aumenta. Así, se ha llevado a cabo un estudio analítico y visual mediante el lenguaje de programación MATLAB., En aquest treball analitzarem els modes de propagació LP (Linearly Polarized) en diferents camins espacials independents, atenent a la densitat energètica dels camps electromagnètics d’aquests modes amb una freqüència normalitzada fixa i també a la seva evolució a mesura que aquesta augmenta. Així, s’ha dut a terme un estudi analític i visual mitjançant el llenguatge de programació MATLAB.

Current microscopy demands the visualization of large threedimensional samples with increased sensitivity, higher resolution, and faster speed. Several imaging techniques based on widefield, point-scanning, and light-sheet strategies have been designed to tackle some of these demands. Although successful, all these require the illuminated volumes to be tightly coupled with the detection optics to accomplish efficient optical sectioning. Here, we break this paradigm and produce optical sections from out-of-focus planes. This is done by extending the depth of field of the detection optics in a lightsheet microscope using wavefront-coding techniques. This passive technique allows accommodation of the light sheet at any place within the extended axial range. We show that this enables quick scanning of the light sheet across a volumetric sample. As a consequence, imaging speeds faster than twice the volumetric video rate (>70 volumes/s) can be achieved without needing to move the sample. These capabilities are demonstrated for volumetric imaging of fast dynamics in vivo as well as for fast, three-dimensional particle tracking., Peer Reviewed, Postprint (published version)

Current microscopy demands the visualization of large three-dimensional samples with increased sensitivity, higher resolution, and faster speed. Several imaging techniques based on widefield, point-scanning, and light-sheet strategies have been designed to tackle some of these demands. Although successful, all these require the illuminated volumes to be tightly coupled with the detection optics to accomplish efficient optical sectioning. Here, we break this paradigm and produce optical sections from out-of-focus planes. This is done by extending the depth of field of the detection optics in a light-sheet microscope using wavefront-coding techniques. This passive technique allows accommodation of the light sheet at any place within the extended axial range. We show that this enables quick scanning of the light sheet across a volumetric sample. As a consequence, imaging speeds faster than twice the volumetric video rate (>70 volumes/s) can be achieved without needing to move the sample. These capabilities are demonstrated for volumetric imaging of fast dynamics in vivo as well as for fast, three-dimensional particle tracking., Peer Reviewed, Postprint (published version)

Realitzar un software de caracterització de polsos lasers ultracurts basats en el mètode Mefisto: Measurement of the electric field by interferometric trace observation., [ANGLÈS] Due to their extremely short time duration and their high intensity, ultrashort laser pulses play an important role in many science and technology fields. In most of their applications, pulses must be characterized before being used, that is to say, their complex electric field must be known. However, that brief time duration makes characterization difficult, and as a result methods based on indirect measurements are needed. One of the techniques that allow ultrashort laser pulses characterization is MEFISTO (Measurement of Electric Fields by Interferometric Spectral Trace Observation), which is able to recover the complex electric field from two ultrashort laser pulses simultaneously and in an analytical way. To achieve this, MEFISTO uses the spectrally resolved interferometric correlation of these pulses, known as interferometric trace. In this Final Degree Project a graphical application which implements MEFISTO practically has been designed and programmed. This application, named betaMEFISTO, comprises two different modes of operation: a theoretical mode and an experimental mode. The first one allows to simulate the electric field of two ultrashort pulses, calculate their interferometric trace, analyze it with MEFISTO algorithms and finally compare obtained fields with original ones. Therefore, theoretical mode offers a tool for studying this characterization technique. On the other hand, experimental mode allows to load and process an interferometric trace obtained in a lab, retrieving the amplitude and phase of the pulses from which the trace was generated. The main goal of betaMEFISTO is to provide a basic working environment for further investigation about MEFISTO. Once the application development has been finished, a study has been carried out in order to evaluate its functionality and utility depending on the used pulses and traces characteristics. Finally, those aspects that should be reinforced and investigated in future projects have also been, [CASTELLÀ] Por su duración extremadamente breve y su elevada intensidad, los pulsos láser ultracortos juegan un importante papel en numerosos ámbitos científicos y tecnológicos. En muchas de las aplicaciones de estos pulsos es necesario caracterizarlos previamente, es decir, conocer cuál es su campo eléctrico complejo. Sin embargo, es precisamente su corta durada lo que dificulta esa caracterización, y lo que provoca que sea necesario usar métodos basados en medidas indirectas. Una de las técnicas que permiten la caracterización de pulsos láser ultracortos es MEFISTO (Measurement of Electric Fields by Interferometric Spectral Trace Observation), capaz de obtener el campo eléctrico complejo de dos pulsos láser ultracortos de manera simultánea y a partir de procedimientos analíticos. Para ello utiliza la correlación interferométrica de los dos pulsos resuelta espectralmente, lo que se conoce como traza interferométrica. En este Proyecto de Final de Carrera se ha diseñado y programado una aplicación gráfica que implementa de forma práctica la técnica MEFISTO. Esta aplicación, llamada betaMEFISTO, cuenta con dos modos de funcionamiento: un modo teórico y un modo experimental. El modo teórico permite simular el campo eléctrico de uno o dos pulsos ultracortos, calcular su traza interferométrica y analizarla usando MEFISTO, pudiendo comparar los campos obtenidos con los campos originales y ofreciendo por tanto una herramienta de estudio sobre esta técnica de caracterización. Por otro lado, el modo experimental permite cargar i procesar una traza interferométrica experimental obtenida en el laboratorio, recuperando el módulo y la fase de los pulsos que la han generado. El objetivo fundamental de betaMEFISTO es ofrecer un entorno a partir del cual se pueda seguir trabajando e investigando alrededor de MEFISTO. Una vez desarrollada la aplicación, se ha estudiado su funcionalidad y su eficacia en función de las características de los pulsos y de las trazas interferométricas us, [CATALÀ] Per la seva durada extremadament breu i la seva elevada intensitat, els polsos làser ultracurts tenen un paper important en nombrosos àmbits científics i tecnològics. En moltes de les aplicacions d’aquests polsos es fa necessari caracteritzar-los prèviament, és a dir, conèixer quin és el seu camp elèctric complex. Però és precisament la seva curta durada el que dificulta aquesta caracterització, i el que fa que sigui necessari usar mètodes basats en mesures indirectes. Una de les tècniques que permet la caracterització de polsos làser ultracurts és MEFISTO (Measurement of Electric Fields by Interferometric Spectral Trace Observation), capaç d’obtenir el camp elèctric complex de dos polsos làser ultracurts de manera simultània i a partir de procediments analítics. Per fer-ho utilitza la correlació interferomètrica dels dos polsos resolta espectralment, coneguda com traça interferomètrica. En aquest Projecte de Final de Carrera s’ha dissenyat i programat una aplicació gràfica que implementa de manera pràctica la tècnica MEFISTO. Aquesta aplicació, anomenada betaMEFISTO, té dos modes de funcionament: un mode teòric i un mode experimental. El mode teòric permet simular el camp elèctric d’un o dos polsos ultracurts, calcular la seva traça interferomètrica i analitzar-la amb MEFISTO, podent comparar els camps obtinguts amb els camps originals i oferint per tant una eina d’estudi sobre aquesta tècnica de caracterització. Per altra banda, el mode experimental permet carregar i processar una traça interferomètrica experimental obtinguda en el laboratori, recuperant el mòdul i la fase dels polsos que l’han generat. L’objectiu fonamental de betaMEFISTO és oferir un entorn a partir del qual es pugui seguir treballant i investigant al voltant de MEFISTO. Un cop desenvolupada l’aplicació, se n’ha estudiat la seva funcionalitat i la seva eficàcia en funció de les característiques dels polsos i de les traces interferomètriques utilitzades. Per acabar, s’han recollit aquell

Light sheet microscopy (LSM) is a new technique that is gaining importance in life sciences. The TFG consist in designing, building, characterizing and testing a new type of LSM., Microscopy has revealed an astonishing new world that was previously invisible to our eyes. Unfortunately, we still have very little knowledge of how life actually works, and for that reason new powerful microscopy techniques have to be developed. The Super Resolution Light Microscopy & Nanoscopy Facility (SLN) led by Dr. Pablo Loza-Alvarez at The Institute of Photonic Sciences (ICFO) is equipped with front-end microscopy techniques that are able to operate a step beyond the commercial state of the art. However, there is a need to incorporate a microscope capable of acquiring fast three-dimensional images of large microscopic samples. One option to fulfil this need, is the implementation of a new light sheet fluorescence microscope, which must be robust and user-friendly for non-specialist users. Light sheet fluorescence microscopy is a relatively new technique that has grown in popularity in the life sciences since its invention, becoming eventually the Nature Method of the Year 2014. Still, it has a great potential to keep advancing. Its ability to image many cells simultaneously within large samples, opens up the possibility of imaging whole organs of small animals such as living hearts, developing embryos and functioning brains. Understanding the global and mysterious properties of the human brain is one of the greatest challenges facing 21st century science, and light sheet fluorescence microscopy can play an important part in it. This technique has already become one of the major imaging tools used to produce dynamic pictures of the brain in The White House BRAIN Initiative, which is aimed at the understanding and cure of devastating diseases such as Alzheimer, Parkinson and Epilepsy. In this work, I will describe the design, implementation and test of the routine light sheet fluorescence microscope that I built in the SLN Facility at ICFO. It is designed to image entire clarified mouse brains but also to provide enough flexibility to image a wide range of lar, La microscopia nos ha revelado un nuevo mundo sorprendente que antes era invisible a nuestros ojos. Desafortunadamente, aún conocemos muy poco sobre cómo funciona la vida y por este motivo se tienen que desarrollar nuevas técnicas de microscopia más potentes. La Super Resolution Light Microscopy & Nanoscopy Facility (SLN) dirigida por el Dr. Pablo Loza-Alvarez en el Instituto de Ciencias Fotónicas (ICFO) está equipada con tecnologías punteras de microscopia capaces de trabajar un paso más allá de los mejores microscopios comerciales. Sin embargo, hay la necesidad de incorporar un microscopio capaz de adquirir con rapidez imágenes tridimensionales de grandes muestras microscópicas. Una opción para llenar este vacío es la implementación de un nuevo microscopio de fluorescencia de hoja de luz, el cual tiene que ser robusto y fácil de utilizar por usuarios no especialistas. La microscopia de fluorescencia de hoja de luz es una técnica relativamente nueva que des de su invención ha ganado popularidad entre los investigadores en ciencias de la vida, llegando finalmente a ser nombrada método del año 2014 por la prestigiosa revista Nature. Sin embargo, aún tiene un gran potencial para seguir avanzando. Su habilidad para visualizar simultáneamente muchas células de grandes muestras abre la posibilidad de conseguir imágenes de órganos enteros de pequeños animales en funcionamiento como por ejemplo corazones, embriones o incluso cerebros. Comprender las propiedades misteriosas del cerebro humano es uno de los mayores retos a los que se enfrenta la comunidad científica del siglo XXI, y la microscopia de fluorescencia de hoja de luz puede jugar un papel muy importante en ello. Esta técnica se ha convertido en una de las herramientas más relevantes a la hora de adquirir imágenes dinámicas del cerebro en la BRAIN Initiative de la Casa Blanca. Éste es un proyecto a gran escala enfocado a entender y curar enfermedades tan devastadoras como lo son el Alzheimer, el Parkinson o la Epil, La microscòpia ens ha revelat un nou món sorprenent que abans ens era invisible als ulls. Desafortunadament, encara coneixem molt poc sobre com funciona la vida i per aquest motiu s’han de desenvolupar noves tècniques de microscòpia més potents. La Super Resolution Light Microscopy & Nanoscopy Facility (SLN) dirigida pel Dr. Pablo Loza-Alvarez a l’Institut de Ciències Fotòniques (ICFO) està equipada amb tecnologies punteres de microscòpia capaces de treballar un pas més enllà dels millors microscopis comercials. Tanmateix, hi ha la necessitat d’incorporar un microscopi amb la capacitat d’adquirir amb rapidesa imatges tridimensionals de grans mostres microscòpiques. Una opció per cobrir aquesta mancança és la implementació d’un nou microscopi de fluorescència de full de llum, el qual ha de ser robust i fàcil d’utilitzar per usuaris no especialistes. La microscòpia de fluorescència de full de llum és una tècnica relativament nova que des de la seva invenció ha guanyat popularitat entre els investigadors en ciències de la vida, arribant finalment a ser distingida com a mètode de l’any 2014 per la prestigiosa revista Nature. Tot i això, encara té un gran potencial per seguir avançant. La seva habilitat per visualitzar simultàniament moltes cèl·lules de grans mostres, obra la possibilitat d’aconseguir imatges d’òrgans sencers de petits animals en funcionament com ara cors, embrions o fins i tot cervells. Comprendre les propietats misterioses del cervell humà és un dels majors reptes a que s’enfronta la comunitat científica del segle XXI i la microscòpia de fluorescència de full de llum pot desenvolupar-hi un paper molt important. Aquesta tècnica s’ha convertit també en una de les eines més rellevants per adquirir imatges dinàmiques del cervell en la BRAIN Initiative de la Casa Blanca. Aquest és un projecte a gran escala que està enfocat a entendre i curar malalties tan devastadores com ara l’Alzheimer, el Parkinson o l’Epilèpsia. En aquest treball descriuré el disseny, l

The preliminary goal of this project is to develop a new approach for illumination strategies within diffuse optical tomography. The student will use advanced Monte Carlo modelling to model different strategies including time gating and structured illumination to study the problem from a theoretical perspective. If the theoretical results a promising, then this will move onto experimental implementation. This is the continuation of the student's original work duringg summer fellowship at the ICFO Medical Optics group.

Guiding light at the nanoscale is usually accomplished using surface plasmons(1-12). However, plasmons propagating at the surface of a metal sustain propagation losses. A different type of surface excitation is the Dyakonov surface wave. These waves, which exist in lossless media, were predicted more than two decades ago(13) but observed only recently(14). Dyakonov surface waves exist when at least one of the two media forming the surface exhibits a suitable anisotropy of refractive indexes. Although propagating only within a narrow range of directions(15), these waves can be used to create modes supported by ultrathin films that confine light efficiently within film thicknesses well below the cutoff thickness required in standard waveguides. Here, we show that 10 nm and 20 nm dielectric nanosheets of aluminium oxide clad between an anisotropic crystal (lithium triborate) and different liquids support Dyakonov-like modes. The direction of light propagation can be controlled by modulating the refractive index of the cladding. The possibility of guiding light in nanometre-thick films with no losses and high directionality makes Dyakonov wave modes attractive for planar photonic devices in schemes similar to those currently employing long-range plasmons., Peer Reviewed, Postprint (published version)

Postprint (published version)

This special issue of Optics & Photonics News highlights the most exciting peer-reviewed optics research to have emerged over the past 12 months., Peer Reviewed, Postprint (published version)

Treball realitzat a l'Institut de Ciències Fotòniques (ICFO), [ANGLÈS] Photovoltaic energy provides a paramount solution capable of meeting all clean energy demands. Solar cells based on inorganic nanoparticles are a hot topic for research due to their potential to harness solar energy in a cost-effective way. Compelling efforts are undertaken to improve their performance to the level of current commercial technologies. However, the state-of-the-art devices still rely on toxic compounds. In this work, we present a novel candidate as a green alternative. Achievements made through material optimization and structural design tailoring result in a threefold power conversion efficiency upgrade., [CASTELLÀ] La energía fotovoltaica proporciona una muy necesaria solución capaz de proveer toda la demanda de energía renovable. Las células solares basadas en nanopartículas inorgánicas son un campo en alza dentro de la investigación científica gracias a su potencial para convertir la energía solar de manera eficiente económicamente. Actualmente se llevan a cabo grandes esfuerzos para acercar su rendimiento al nivel de las tecnologías comerciales existentes, pero los mejores resultados se han obtenido con compuesto tóxicos. En este trabajo se presenta un novedoso material como alternativa ecológica. Los logros en la optimización del material y la modificación de la estructura y procesado consiguen que la eficiencia inicial se triplique., [CATALÀ] L'energia fotovoltaica proporciona una molt necessària solució capaç de complir amb tota la demanda d'energia ecològica. Les cèl·lules solars basades en nanopartícules inorgàniques són un camp en alça dins de la recerca científica gràcies al seu potencial per convertir l'energia solar d'una forma eficient a nivell econòmic. Actualment es porten a terme grans esforços per apropar el seu rendiment al nivell de les tecnologies comercials existents avui en dia, però els millors resultats s'obtenen amb materials tòxics. En aquest treball es presenta un novedós candidat com a alternativa verda. Els assoliments aconseguits a través de l'optimització del material i la modificació de l'estructura i el seu processament han fet que es tripliquin els resultats inicials.

Fast imaging of molecular changes under high-resolution and label-free conditions are essential for understanding in-vivo processes, however, current techniques are not able to monitor such changes in real time. Polarization sensitive second harmonic generation (PSHG) imaging is a minimally invasive optical microscopy technique capable of quantifying molecular conformational changes occurring below the diffraction limit. Up to now, such information is generally retrieved by exciting the sample with different linear polarizations. This procedure requires the sample to remain static during measurements (from a few second to minutes), preventing the use of PSHG microscopy from studying moving samples or molecular dynamics in living organisms. Here we demonstrate an imaging method that is one order of magnitude faster than conventional PSHG. Based on circular polarization excitation and instantaneous polarimetry analysis of the second harmonic signal generated in the tissue, the method is able to instantaneously obtain molecular information within a pixel dwell time. As a consequence, a single scan is only required to retrieve all the information. This allowed us to perform PSHG imaging in moving C. elegans, monitoring myosin’s dynamics during the muscular contraction and relaxation. Since the method provides images of the molecular state, an unprecedented global understanding of the muscles dynamics is possible by correlating changes in different regions of the sample., Peer Reviewed, Postprint (published version)