Dissertations / Theses on the topic 'Visible and infrared photoinitiators'

Ces dernières années, la photopolymérisation a fait l'objet d'intenses efforts de recherche en raison de la croissance constante des applications industrielles. C’est un processus rapide pouvant être réalisée à température ambiante, sans solvant et permettant d'obtenir un contrôle spatial et temporel de la polymérisation. Ces dernières années, l'utilisation de conditions d'irradiation douce qui constitue une alternative aux procédés de photopolymérisation UV à l'origine de nombreux soucis de sécurité est activement recherchée. Par conséquent, le développement de nouveaux systèmes photoamorceurs absorbant fortement dans la région visible ou du proche infra-rouge sont activement recherchés par les communautés académiques et industrielles. Néanmoins, même si certains résultats sont prometteurs, les systèmes reportés sont souvent caractérisés par des réactivités modérées et rivalisent difficilement avec les systèmes UV actuels. Dans ce contexte, nous avons synthétisé une large librairie de molécules photosensibles capables d’absorber la lumière dans le domaine du visible ou du proche infrarouge et capables d’amorcer une réaction de polymérisation avec un système photoamorceur basée sur la catalyse photoredox. Dans ce manuscrit, nous présentons aussi bien la synthèse et les capacités de polymérisation de différentes familles de colorants. Leurs propriétés photochimiques ont également été étudiées par spectrométrie UV-visible, luminescence, photolyse, surveillance de la température et expériences de résonance paramagnétique électronique. Des applications telles que l'impression 3D et les expériences d'écriture laser sont également présentées
In recent years, photopolymerization has been the subject of intense research efforts due to the constant growth of industrial applications. It is a quick process that can be performed at room temperature, solvent-free conditions and enables to get a spatial and a temporal control of the polymerization process. In recent years, the use of irradiation conditions that constitutes an alternative to the UV photopolymerization processes at the origin of numerous safety concerns are actively researched. Therefore, the development of new photoinitiating systems which absorb strongly in the visible or near infrared region are actively researched by both the academic and industrial communities. Nevertheless, even if some results are promising, the reported systems are often characterized by moderate reactivities and hardly compete with current UV systems. In this context, we have synthesized a large library of photosensitive molecules capable of absorbing light in the visible or near infrared range and capable of initiating a polymerization reaction with a photoinitiating system based on photoredox catalysis. In this manuscript, we present both the synthesis and the polymerization abilities of different families of dyes. Their photochemical properties were also studied by UV-Visible spectrometry, luminescence, photolysis, temperature monitoring and electronic paramagnetic resonance experiments. Applications such as 3D printing and laser write experiments are also presented

Recientes avances en im agenes t ermicas (LWIR) han permitido su uso en aplicaciones m as all a del ambito militar. Actualmente, esta nueva familia de sensor esta siendo incluida en diversas aplicaciones tanto t ecnicas como cient cas. Este tipo de sensores facilitan tareas tales como: detecci on de peatones, puntos calientes, detecci on de cambios de temperatura, entre otros. Caracter sticas que pueden mejorar signi cativamente el desempeo de un sistema, especialmente cuando hay interacci on con humanos. Por ejemplo, aplicaciones de v deo vigilancia, detecci on de peatones, an alisis de postura. En esta tesis se plantea entre otras la siguiente pregunta de investigaci on: Podr a un par de sensores operando en diferentes bandas del espectro electromagn etico, como el visible e infrarrojo t ermico, proporciona informaci on de profundidad? Si bien es una cuesti on compleja, nosotros demostramos que un sistema de estas caracter sticas es posible. Adem as, de discutir sus posibles ventajas, desventajas y oportunidades potenciales. La fusi on y correspondencia de los datos procedentes de diferentes sensores, como las emisiones registradas en la banda visible e infrarroja, representa un reto atractivo, ya que se ha demostrado que aquellas se~nales est an d ebilmente correlacionadas. Por lo tanto, muchas t ecnicas tradicionales de procesamiento de im agenes y visi on por computadora son inadecuadas, requiriendo ajustes para su correcto funcionamiento. En esta investigaci on se realizo un estudio experimental comparando diferentes funciones de costos multimodal, y t ecnicas de correspondencia, a n de construir un sistema est ereo multimodal. Tambi en, se identi c o el problema com un entre est ereo visible/ visible y infrarrojo/visible, particularmente en ambientes al aire libre. Entre las contribuciones de esta tesis se encuentra; el aislamiento de las diferentes etapas que componen un sistema est ereo multimodal. Esta arquitectura es gen erica a diferentes niveles, tanto computacional, funcional y estructural, permitiendo su extensi on a esquemas mas complejos tales como fusi on de alto nivel (sem antica) y de orden superior (supuestos). El enfoque propuesto est a destinado a explorar nuevos m etodos de correspondencia est ereo, pasando de una soluci on escasa a una densas (tanto en disparidad como en mapas de profundidad). Adem as, se ha incluido informaci on de contexto en forma de asunciones y restricciones. Finalmente, esta disertaci on muestra un promisorio camino hacia la integraci on de m ultiples sensores.
Recent advances in thermal infrared imaging (LWIR) has allowed its use in applications beyond of military domain. Nowadays, this new sensor family is included in diverse technical and scienti c applications. They o er features that facilitate tasks, such as detection of pedestrians, hot spots, di erences in temperature, among others, which can signi cantly improve the performance of a system where the persons are expected to play the principal role. For instance, video surveillance applications, monitoring, and pedestrian detection. During this dissertation is stated the next question: Could a couple of sensors measuring di erent bands of the electromagnetic spectrum, as the visible and thermal infrared, provides depth information? Although is a complex question, we shows that a system of those characteristics is possible as well as their advantages, drawbacks, and potential opportunities. The fusion and matching of data coming from di erent sensors, as the emissions registered at visible and infrared band, represents a special challenge, because it has been showed that theses signals are weak correlated. Indeed, they are uncorrelated. Therefore, many traditional techniques of image processing and computer vision are not helpful, requiring adjustments for their correct performs in every modality. In this research is performed a experimental study that compares di erent cost functions and matching approaches, in order to build a multimodal stereo system. Furthermore, are identi ed the common problem between visible/visible and infrared/visible stereo, special in the outdoor scenes. A contribution of this dissertation is the isolation achieved, between the di erent stage that compose a multimodal stereo system. Our framework summarizes the architecture of a generic stereo algorithm, at di erent levels: computational, functional, and structural, which is successful because this can be extended toward high-level fusion (semantic) and high-order (prior). The proposed framework is intended to explore novel multimodal stereo matching approaches, going from sparse to dense representation (both disparity and depth maps). Moreover, context information is added in form of priors and assumptions. Finally, this dissertation shows a promissory way toward the integration of multiple sensors for recovering three-dimensional information.

Upconversion phosphor materials are attracting considerable attention for their possible applications in solar cells with improved efficiency, nanomaterials for bio-imaging, lasers and novel display technologies. Upconversion materials, usually consisting of crystals dopedwith lanthanide ions, can convert low-energy incident radiation into higher energy emittedradiation. Several mechanisms are involved, including multiple photon absorption and energy transfers between dopants. Up to now, reported upconversion efficiencies have beenrelatively low, excitation thresholds quite high, and the investigated phosphors (generally fluorides) often presented poor chemical stability (hygroscopy), limiting their industrial applicability. In this dissertation, we investigate the upconversion luminescence characteristics of rareearth-doped RE2BaZnO5 (RE = Y, Gd) phosphors, for near-infrared to visible upconversion. Being oxides, these materials have good chemical, thermal and mechanical properties. A variety of dopants, including Yb3+, Er3+, Ho3+ and Tm3+, were embedded in the host lattice, resulting in bright red, green, blue and white light emissions under 980 nm excitation and at relatively low excitation powers. Upconversion efficiencies up to ~ 5.2%, 2.6%, 1.7% and 0.3% were respectively achieved in samples doped with Yb3+, Er3+ (green and red emission), Yb3+, Ho3+ (green emission), Yb3+, Tm3+ (blue and near-infrared emission) and Yb3+, Er3+, Tm3+ (white light emission). We believe that our green, red and white emitting systems are the most efficient upconverting samples reported to date for green, red and whitelight emission, which makes them serious candidates for many of the applications listed above. The upconversion mechanisms were determined for the first time by means of indepth steady-state and time-resolved spectroscopic investigations, including concentration and power dependence studies associated with temperature-dependent lifetime measurements.

The potential of different spectroscopic techniques for evaluating potato (Solanum tuberosum L.) quality was investigated. Spectral data in the wavelength range of 400-1750 nm were used to develop quality prediction models. The Partial Least Squares (PLS) regression was used for predicting the water content in potato samples. Water content was predicted with R2 ≥ 0.938.
A further study was conducted to find the best wavelengths for predicting water content using two methods, PLS and multiple linear regression. Wavelength ranges of 910-1020, 1129-1211, 1363-1403 nm were selected for samples without skin, while 700-900, 930-1050, 1100-1300, 1400-1550 nm were selected for samples with-skin. Weight prediction models were established using the predicted water content.
Visible spectroscopy was used for classifying shriveled and non-shriveled potatoes. The wavelength ranges best suited to such a classification were those of 442-452, 456-466, 641-651, and 684-694 nm, with accuracies as high as 94.28% and as low as 80%.

Since its discovery in 2004, graphene, a one-atom-thick layer of carbon atoms arranged in a hexagonal lattice, has attracted huge interest from the scientific community due to its extraordinary electronic, mechanical, and optical properties. While most of the earliest studies focused on electronic transport, in recent years the fields of graphene photonics and optoelectronics have thriven. The goal of this thesis is to explore the use of graphene for novel optoelectronic devices, adopting different approaches to enhance the electrically tunable graphene-light interaction in a broad spectral range, from the visible to the mid-infrared. This includes investigating the sub-wavelength interaction and energy transfer between a dipole and a graphene sheet, as well as working on efficient photodetection schemes. Indeed graphene high electronic mobility, broadband absorption, flexibility and tunable optoelectronic properties (described in Chapter 1) make it extremely appealing for the development of optoelectronic applications with new functionalities. Concerning the devices, the starting point of the experiments presented in the thesis are graphene field effect transistors of different geometries, whose fabrication and characterization techniques are described in Chapter 2. The tunability of the optoelectronic properties via control over the Fermi energy is an essential feature of the fabricated devices. The change in the Fermi level is achieved applying a voltage to a back-gate or a polymer electrolyte top-gate. We address both aspects at the core of optoelectronics, i.e. the control of optical properties with electric fields and the modification of electrical quantities, such as current, with light. Therefore the first part of the thesis (comprising Chapter 3, 4 and 5) is devoted to graphene nanophotonics and plasmonics, while the second part deals with graphene-based photodetection (Chapter 6, 7, 8 and 9). In Chapter 3, the main concepts at the basis of graphene nanophotonics are presented, such as the electrical tunability and the strong field confinement of the 2D plasmons, as well as the coupling of an optical emitter to graphene plasmons or electron-hole pair excitations. Then we present two experiments showing the control of light by means of static electric fields. In Chapter 4 we show the electrical control of the relaxation pathways of erbium ions in close proximity to a graphene sheet: the energy flow from the emitters is tuned to electron-hole pairs in graphene, to free space photons and to plasmons by changing the graphene Fermi level. In Chapter 5 we present the real-space imaging and tuning of highly confined graphene plasmons in the mid-infrared, launched by the dipole of a metallized s-SNOM tip (Chapter 5). In this case modifying the graphene Fermi level leads to a change in the plasmon wavelength. In Chapter 6 we review existing schemes for graphene photodetectors and the main mechanisms enabling photodetection with graphene, with particular emphasis toward the photothermoelectric effect. Then we present three cases where graphene photoresponse is enhanced exploiting the interaction with surrounding materials. A hybrid graphene-quantum dot photodetector in the visible and near-infrared is reported in Chapter 7: a photogating effect after light absorption in the quantum dots leads to extremely high responsivities (over one million A/W). In Chapter 8 we demonstrate how the excitation of bulk phonons of a polar substrate enhances the mid-infrared photocurrent via a photothermoelectric effect. Also substrate surface phonons, launched by illuminating a metal edge with light polarized perpendicularly to it, lead to an increase in the photoresponse, as described in Chapter 9. The results presented in this thesis open new avenues in the field of graphene-based optoelectronics for active nano-photonics and sensing.
Desde su descubrimiento en 2004, el grafeno, una sola capa átomos de carbono en un retículo hexagonal, ha atraído un gran interés de la comunidad científica debido a sus propiedades electrónicas, mecánicas y ópticas extraordinarias. Los primeros estudios se centraron en el transporte electrónico, pero en los últimos años estudios en el campo de la fotónica y de las propiedades optoelectrónicas del grafeno han suscitado un mayor interés. El objetivo de esta tesis es explorar el uso del grafeno para nuevos dispositivos optoelectrónicos, adoptando diferentes enfoques para mejorar la interacción del grafeno con la luz en un amplio rango espectral, desde el rango visible hasta el infrarrojo medio. Esto incluye la investigación de la interacción y la transferencia de energía entre un dipolo y una monocapa de grafeno cercana, así como trabajar en esquemas de fotodetección eficientes. La alta movilidad electrónica, la absorción de banda ancha, la flexibilidad y las propiedades optoelectrónicas sintonizables (véase Capítulo 1) hacen que el grafeno sea extremadamente atractivo para el desarrollo de aplicaciones optoelectrónicas con nuevas propiedades funcionalidades. En cuanto a los dispositivos, el punto de partida de los experimentos presentados en esta tesis son transistores de efecto de campo con diferentes geometrías, cuya fabricación y técnicas de caracterización se describen en el Capítulo 2. La capacidad de ajuste de las propiedades optoelectrónicas a través del control de la energía de Fermi es una característica esencial de los dispositivos, y se logra con la aplicación de un voltaje de puerta. Nos dirigimos a ambos aspectos a la base de la optoelectrónica, es decir, el control de las propiedades ópticas con campos eléctricos y la modificación de magnitudes eléctricas, como la corriente con la luz incidente. Por tanto, la primera parte de la tesis (Capítulos 3, 4 y 5) se dedica al estudio de la nanofotónica y plasmónica del grafeno, mientras que la segunda parte se ocupa de fotodetección basada en grafeno (Capítulos 6, 7, 8 y 9). En el Capítulo 3, se explican los principales conceptos del campo de la nanofotónica de grafeno, como la capacidad de ajuste eléctrico y el fuerte confinamiento de los plasmones 2D, así como el acoplamiento de un emisor óptico con los plasmones o pares electrón-hueco. Luego se presentan dos experimentos que muestran el control de la luz por medio de campos eléctricos estáticos. En el Capítulo 4 se muestra el control eléctrico de las vías de relajación de iones de erbio en las proximidades de una monocapa de grafeno: el flujo de energía a partir de los emisores se puede dirigir a pares electrón-hueco en el grafeno, a fotones y a plasmones cambiando el nivel de Fermi del grafeno. En el Capítulo 5 se presenta la excitación y el ajuste de plasmones de grafeno altamente confinados en el infrarrojo medio, activado mediante el dipolo de una punta de microscopia de campo cercano (Capítulo 5). En el Capítulo 6 se revisan los fotodetectores de grafeno existentes y los principales mecanismos que permitan fotodetección con grafeno. A continuación se presentan tres casos donde la fotorrespuesta del grafeno se mejora con la explotación de la interacción con los materiales circundantes. Un fototransistor híbrido de grafeno y puntos cuánticos (véase Capitulo 7) llega a responsividad extremadamente alta en el visible y infrarrojo cercano (más de un millón de A/W). En el Capítulo 8 se demuestra cómo la excitación de fonones de bulk de un sustrato polar aumenta la fotocorriente en el infrarrojo medio a través de un efecto fototermoeléctrico. También fonones superficie del sustrato, lanzados por la iluminación de un borde de metal con luz polarizada perpendicularmente, conducen a un aumento en la fotorrespuesta (Capítulo 9). Los resultados presentados en esta tesis abren nuevos caminos en el campo de la optoelectrónica basada en el grafeno en el campo de la nano-fotónica activa y de los sensores

Egg is a fragile component within the human diet. Important changes occur in egg during storage. Prediction of these changes is critical in order to grade the eggs upon their quality and freshness. The objectives of this study were to evaluate the application of visible and near infrared spectroscopy as a non-destructive method for the assessment of egg quality and freshness. Therefore, visible and near infrared transmittance spectral data ranging from 350 to 2500 nm was collected with the help of a radiospectrometer on 360 freshly laid eggs. A partial least squares model was built in order to link the spectral data with the most widely used destructive methods, namely Haugh Units and albumen pH in terms of egg quality and the number of storage days in terms of egg freshness. The ability of maximum R2 method to select the relevant wavelengths in order to build a partial least squares (PLS) predictive model was investigated in the first part of the study. The results showed that this method improved the predictive ability of the model. Coefficient of determination (R2) and root mean square error of cross validation (RMSECV) were calculated in order to select sets of wavelengths to build the model with the best predictive ability. The second part of the study was based on building calibration models for predicting egg freshness in terms of number of storage day and egg quality in terms of Haugh Units and albumen pH. The results showed that the models had good predictive ability and R2 for number of storage days, Haugh Units and albumen pH were 0.89, 0.79 and 0.90, respectively. RMSECV for these three parameters were 1.65, 5.05 and 0.06, respectively.
L'oeuf est un composant fragile dans le regime alimentaire humain. Des changements importants arrivent dans loeuf pendant le stockage. La prediction de ces changements eat ctitique pour classer les oeufs selon leur qualité et leur fraîcheur. Les objectifs de cette étude étaient d'évaluer l'application méthode basée sur la spectroscopie visible et infra-rouge proche comme une method non destructive pour l'évaluation de la qualité et la fraîcheur des oeufs. Donc, la transmission visible et infra rouge proche des données spectrales aux limites de 350 à 2500 nm ont été exécutées à l'aide d'un radiosectromètre sur 360 oeufs récemment pondus. Un modèle des moindres carrées partiels (MCP) a été construit afin de lier les données soectrakes avec les méthodes destructives les plus utilisées, à savoir Unité de Haugh at le pH d'albumen en termes de qualité d'oeufs et le nombre de jours de stoclage en termees de fraîcheur d'oeufs. La première étude a traité de la capacité de la méthode maximum R2 à choisir les longueurs d'onde appropriées afin d'établir un modèle des moindres carrés partiels (MCP). Les résultats ont révélé combien cette méthode a été un bon outil dans le choix des longueurs d'onde instructives et dans l'amélioration de la capacité prédictive du modèle. Le coefficient de détermination (R2) et les erreurs de la racine carrée moyenne (ERCM) ont été calculés afin de choisir des ensembles de longueurs d'onde, lesquels aident le mieux à construire le modèle qui possède la meilleure capacité prédictive. La seconde étude a visé l'établissement des modèles prédictifs de la fraîcheur d'oeufs en fonction du n

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004.
Includes bibliographical references (leaves 40-42).
Comets have historically been defined as objects that experience the formation of a "head" (coma) or "tail" as ice and other volatiles that comprise their chemical makeup vaporize when they near the sun. Comets can lose this ability to form a coma or tail, however, through a variety of dynamical processes, creating objects that could chemically be comets but that do not fit the traditional definition. Thus, a new challenge has arisen to correctly define the properties that differentiate comets and asteroids. In this study, a number of cometary candidates were observed in visible and infrared wavelengths in an attempt to correctly classify them as asteroids or dormant or extinct comets. From this data, two groups of objects were identified: one group of possible cometary candidates, and one group of likely outer asteroid belt origin objects. From this and other studies, a broader picture of solar system dynamics can be achieved that will give much insight into not only the current dynamical processes that control interplanetary bodies, but also processes that were important in the formation and stratification of the solar system at its birth.
by Alison J. Klesman.
S.M.

The compositional distribution of asteroids provides clues to understanding solar system formation and evolutionary processes in the asteroid belt. The surface mineralogy and distribution of volatiles on asteroids is determined using visible and near-infrared spectroscopy. A revised asteroid taxonomy is developed which incorporates compositional information from the near-infrared asteroid spectra. A search is conducted for organic compounds on distant asteroids, thought to be most volatile-rich in composition. Our near-infrared spectroscopy of outer belt asteroids shows a trend of increasing red continuum slope with heliocentric distance. I interpret this trend as a compositional change, possibly due to increasing abundance of complex organic compounds on these more distant objects. I do not observe a CN absorption band near 2.2 $\mu$m, and conclude that the organics present are not primarily CN-bearing solids. The 3-$\mu$m water absorption band is not detected on distant D asteroids, but is seen on main belt D asteroids. This observation is consistent with the idea that D asteroids are volatile-rich, but the object must be heated in order to transform the silicates into hydrated minerals. No evidence of clay minerals is seen on any of the distant asteroids observed. The majority of the Jupiter Trojan asteroids have a uniform spectral appearance in spite of collisional processing, which implies that the dark red surface material is not a thin surface coating, but is representative of the bulk composition. Observations of near-Earth asteroids indicates a wide range of compositions, suggesting a variety of source regions. Two objects are detected which may contain hydrated minerals, a valuable resource in space. Three near-Earth asteroids are studied in detail, revealing a range of pyroxene chemistry and olivine content inconsistent with ordinary chondrite composition. The occurrence of spectral variability, and implied compositional inhomogeneity is approximately 20%, and on spatial scales as small as tens of meters. This observation implies that asteroids are geologically complex, not chemically uniform, as is often assumed in meteorite studies.

In California, natural vegetation is experiencing an increasing amount of stress due to prolonged droughts, wildfires, insect infestation, and disease. Remote sensing technologies provide a means for monitoring plant species presence and function temporally across landscapes. In this his dissertation, I used hyperspectral visible shortwave infrared (VSWIR), hyperspectral thermal (TIR), and hyperspectral VSWIR + broadband TIR imagery to derive key observations of plant species across a gradient of environmental conditions and time frames. In Chapter 2, I classified plant species using hyperspectral VSWIR imagery from 2013–2015 spring, summer, and fall. Plant species maps had the highest classification accuracy using spectra from a single date (mean kappa 0.80–0.86). The inclusion of spectra from other dates decreased accuracy (mean kappa 0.78–0.83). Leave-one-out analysis emphasized the need to have spectra from the image date in the classification training, otherwise classification accuracy dropped significantly (mean kappa 0.31–0.73). In Chapter 3, I used hyperspectral TIR imagery to determine the extent that high precision spectral emissivity and canopy temperature can be exploited for vegetation research at the canopy level. I found that plant species show distinct spectral separation at the leaf level, but separability among species is lost at the canopy level. However, species’ canopy temperatures exhibited different distributions among dates and species. Variability in canopy temperatures was largely explained by LiDAR derived canopy structural attributes (e.g. canopy density) and the surrounding environment (e.g. presence of pavement). In Chapter 4, I used combined hyperspectral VSWIR and broadband TIR imagery to monitor plant stress during California’s 2013–2015 severe drought. The temperature condition index (TCI) was calculated to measure plant stress by using plant species’ surface minus air temperature distributions across dates. Plant stress was not evenly distributed across the landscape or time with lower elevation open shrub/meadows, showing the largest amount of stress in June 2014, and August 2015 imagery. Plant stress spatial variability across the study area was related to a slope’s aspect with highly stressed plants located on south or south-southwest facing slopes. Overall, this dissertation quantifies the ability to temporally study plant species using hyperspectral VSWIR, hyperspectral TIR, and combined VSWIR+TIR imagery. This analysis supports a range of current and planned missions including Surface Biology and Geology (SBG), Environmental Mapping and Analysis Program (EnMAP), National Ecological Observatory Network (NEON), Hyperspectral Thermal Emission Spectrometer (HyTES), and ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS).

Biometric Recognition refers to the automatic identification of a person based on his or her anatomical characteristic or modality (i.e., fingerprint, palmprint, face) or behavioural (i.e., signature) characteristic. It is a fundamental key issue in any process concerned with security, shared resources, network transactions among many others. Arises as a fundamental problem widely known as recognition, and becomes a must step before permission is granted. It is supposed that protects key resources by only allowing those resources to be used by users that have been granted authority to use or to have access to them. Biometric systems can operate in verification mode, where the question to be solved is Am I who I claim I am? or in identification mode where the question is Who am I? Scientific community has increased its efforts in order to improve performance of biometric systems. Depending on the application many solutions go in the way of working with several modalities or combining different classification methods. Since increasing modalities require some user inconvenience many of these approaches will never reach the market. For example working with iris, face and fingerprints requires some user effort in order to help acquisition. This thesis addresses hand-based biometric system in a thorough way. The main contributions are in the direction of a new multi-spectral hand-based image database and methods for performance improvement. The main contributions are: A) The first multi-spectral hand-based image database from both hand faces: palmar and dorsal. Biometric database are a precious commodity for research, mainly when it offers something new like visual (VIS), near infrared (NIR) and thermography (TIR) images at a time. This database with a length of 100 users and 10 samples per user constitute a good starting point to check algorithms and hand suitability for recognition. B) In order to correctly deal with raw hand data, some image preprocessing steps are necessary. Three different segmentation phases are deployed to deal with VIS, NIR and TIR images specifically. Some of the tough questions to address: overexposed images, ring fingers and the cuffs, cold finger and noise image. Once image segmented, two different approaches are prepared to deal with the segmented data. These two approaches called: Holistic and Geometric define the main focus to extract the feature vector. These feature vectors can be used alone or can be combined in some way. Many questions can be stated: e.g. which approach is better for recognition?, Can fingers alone obtain better performance than the whole hand? and Is thermography hand information suitable for recognition due to its thermoregulation properties? A complete set of data ready to analyse, coming from the holistic and geometric approach have been designed and saved to test. Some innovative geometric approach related to curvature will be demonstrated. C) Finally the Biometric Dispersion Matcher (BDM) is used in order to explore how it works under different fusion schemes, as well as with different classification methods. It is the intention of this research to contrast what happen when using other methods close to BDM like Linear Discriminant Analysis (LDA). At this point, some interesting questions will be solved, e.g. by taking advantage of the finger segmentation (as five different modalities) to figure out if they can outperform what the whole hand data can teach us.
El Reconeixement Biomètric fa referència a la identi cació automàtica de persones fent us d'alguna característica o modalitat anatòmica (empremta digital) o d'alguna característica de comportament (signatura). És un aspecte fonamental en qualsevol procés relacionat amb la seguretat, la compartició de recursos o les transaccions electròniques entre d'altres. És converteix en un pas imprescindible abans de concedir l'autorització. Aquesta autorització, s'entén que protegeix recursos clau, permeten així, que aquests siguin utilitzats pels usuaris que han estat autoritzats a utilitzar-los o a tenir-hi accés. Els sistemes biomètrics poden funcionar en veri cació, on es resol la pregunta: Soc jo qui dic que soc? O en identi cació on es resol la qüestió: Qui soc jo? La comunitat cientí ca ha incrementat els seus esforços per millorar el rendiment dels sistemes biomètrics. En funció de l'aplicació, diverses solucions s'adrecen a treballar amb múltiples modalitats o combinant diferents mètodes de classi cació. Donat que incrementar el número de modalitats, representa a la vegada problemes pels usuaris, moltes d'aquestes aproximacions no arriben mai al mercat. La tesis contribueix principalment en tres grans àrees, totes elles amb el denominador comú següent: Reconeixement biometric a través de les mans. i) La primera d'elles constitueix la base de qualsevol estudi, les dades. Per poder interpretar, i establir un sistema de reconeixement biomètric prou robust amb un clar enfocament a múltiples fonts d'informació, però amb el mínim esforç per part de l'usuari es construeix aquesta Base de Dades de mans multi espectral. Les bases de dades biomètriques constitueixen un recurs molt preuat per a la recerca; sobretot si ofereixen algun element nou com es el cas. Imatges de mans en diferents espectres electromagnètics: en visible (VIS), en infraroig (NIR) i en tèrmic (TIR). Amb un total de 100 usuaris, i 10 mostres per usuari, constitueix un bon punt de partida per estudiar i posar a prova sistemes multi biomètrics enfocats a les mans. ii) El segon bloc s'adreça a les dues aproximacions existents en la literatura per a tractar les dades en brut. Aquestes dues aproximacions, anomenades Holística (tracta la imatge com un tot) i Geomètrica (utilitza càlculs geomètrics) de neixen el focus alhora d'extreure el vector de característiques. Abans de tractar alguna d'aquestes dues aproximacions, però, és necessària l'aplicació de diferents tècniques de preprocessat digital de la imatge per obtenir les regions d'interès desitjades. Diferents problemes presents a les imatges s'han hagut de solucionar de forma original per a cadascuna de les tipologies de les imatges presents: VIS, NIR i TIR. VIS: imatges sobre exposades, anells, mànigues, braçalets. NIR: Ungles pintades, distorsió en forma de soroll en les imatges TIR: Dits freds La segona àrea presenta aspectes innovadors, ja que a part de segmentar la imatge de la ma, es segmenten tots i cadascun dels dits (feature-based approach). Així aconseguim contrastar la seva capacitat de reconeixement envers la ma de forma completa. Addicionalment es presenta un conjunt de procediments geomètrics amb la idea de comparar-los amb els provinents de l'extracció holística. La tercera i última àrea contrasta el procediment de classi cació anomenat Biometric Dispersion Matcher (BDM) amb diferents situacions. La primera relacionada amb l'efectivitat respecte d'altres mètode de reconeixement, com ara l'Anàlisi Lineal Discriminant (LDA) o bé mètodes com KNN o la regressió logística. Les altres situacions que s'analitzen tenen a veure amb múltiples fonts d'informació, quan s'apliquen tècniques de normalització i/o estratègies de combinació (fusió) per millorar els resultats. Els resultats obtinguts no deixen lloc per a la confusió, i són certament prometedors en el sentit que posen a la llum la importància de combinar informació complementària per obtenir rendiments superiors.

Fog and haze can have a dramatic impact on vision systems for land and sea vehicles. The impact of such conditions on infrared images is not as severe as for standard images. By fusing images from two cameras, one ordinary and one near-infrared camera, a complete dehazing system with colour preservation can be achieved. Applying several different algorithms to an image set and evaluating the results, the most suitable image fusion algoritm has been identified. Using an FPGA, a programmable integrated circuit, a crucial part of the algorithm has been implemented. It is capable of producing processed images 30 times faster than a laptop computer. This implementation lays the foundation of a real-time dehazing system and provides a significant part of the full solution. The results show that such a system can be accomplished with an FPGA.

This work describes observations of Saturn's atmosphere in the visible and near infrared (450-1000 nm) including four hydrogen quadrupole lines, 17 methane absorption bands ranging over three orders of magnitude in absorption strength, an ammonia absorption band, and the absolute calibrated continuum spectrum. All observations have complete coverage of Saturn's disk, in latitude as well as in center-to-limb position. The accuracy of the data is comparable or better than previous data. This data set gives a quite complete description of Saturn's atmosphere in the visible and near infrared at the spatial resolution of ground based observations. While the main data were acquired in 1988, small changes between 1986 and 1989 were determined also. An atmospheric model is given which fits all observations within estimated errors. It has clear gas at the top of the atmosphere, an extended haze layer and a reflective cloud at the bottom. Pressure levels and the haze optical depth were determined as a function of latitude. The single scattering albedo spectrum of the particles (most likely ammonia ice crystals) is also given for each latitude. The methane mixing ratio is (3.0 ± 0.6) x 10⁻³, the ammonia mixing ratio is (1.2 + 0.8/-0.6) x 10⁻³ below the ammonia condensation level. Room temperature methane absorption spectra do not fit the observed spectra for any cloud structure. A cold temperature methane absorption spectrum is determined under the assumption that methane band strengths are temperature invariant, but not necessarily the absorption coefficients at each location across the band. It indicates that the absorption coefficients are typically 20-30 per cent stronger in the center of a band and up to a factor of two weaker in the wings. This spectrum should be useful in the interpretation of methane observations of all the giant planets and Titan.

Cette thèse est axée sur le domaine de la communication optique sans fil en intérieur pour la surveillance de la santé basée sur des capteurs corporels. L’état de l'art des communications optique sans fil dans les domaines infrarouge, visible et UV ainsi que l'analyse des systèmes liés à la santé utilisant cette technologie ont été fournis. Cela a permis de définir les objectifs et l'orientation de cette thèse. Nous avons étudié l'utilisation de la technologie infrarouge pour la transmission de données entre un capteur porté par un patient et des récepteurs situés aux coins d'un panneau d'éclairage central au plafond de l'environnement. Un lien en visible a été utilisé pour la transmission de données du luminaire vers le patient portant un smartphone équipé d'un décodeur. Les principaux défis étaient la robustesse des liens infrarouge et visible en ce qui concerne la mobilité du patient et l'impact du corps de l'utilisateur en raison de l'emplacement du capteur. Les simulations de canaux réalisées grâce à la technique de Ray-Tracing associée à la méthode de Monte-Carlo ont permis de déterminer le gain de canal qui est le paramètre principal représentant la performance. En raison de la mobilité du patient, l'analyse a été réalisée de manière statistique et en tenant compte de différents emplacements du capteur sur le corps, de la cheville à l'épaule. Les paramètres physiques et géométriques optimaux relatifs aux émetteurs et aux récepteurs afin de garantir les meilleures performances ont été déduites. Il a été démontré qu’il est essentiel de modéliser la présence du corps pour les deux liaisons montante et descendante. Les performances globales du système ont mis en évidence le potentiel des transmissions sans fil entièrement optiques pour la surveillance médicale basée sur des capteurs corporels. Cela a été en partie confirmé par des expérimentations menées à partir de prototypes de capteur communicant en infrarouge et de produits commerciaux pour la liaison en visible
This thesis is focused on the field of indoor optical wireless communication for health monitoring based on body sensors. The state of the art of optical wireless in the infrared, visible and UV domains as well as the analysis of health related systems using this technology have been provided. This helped to define the objectives and orientations of this thesis. We have studied the use of infrared technology for data transmission between a sensor worn by a patient and receivers located at the corners of a central lighting panel at the ceiling of the environment. A link in visible was used for the transmission of data from the luminaire to the patient carrying a smartphone equipped with a decoder. The main challenges were the robustness of the infrared and visible links with regard to patient mobility and the impact of the user's body due to the location of the sensor. The channel simulations performed using the Ray-Tracing technique associated with the Monte-Carlo method allowed determining the channel gain, which is the main parameter representing the performance. Due to the patient mobility, the analysis was performed statistically and taking into account different locations of the sensor on the body, from the ankle to the shoulder. The optimal physical and geometrical parameters for transmitters and receivers to ensure the best performance have been deduced. It has been shown that it is essential to model the presence of the body for both uplink and downlink. The overall performance of the system has highlighted the potential of fully optical wireless transmissions for medical surveillance based on body sensors. This has been partly confirmed by experiments carried out from infrared communicating sensor prototypes and commercial products for the visible link

L' ATP es una molecula clau en el metabolisme cel.lular, actuant com a donador d'energia lliure i acoplant reaccions endergoniques i exergoniques. L'ATP es sintetitzat a la mitocondria en un proces anomenat fosforil.lacio oxidativa despres d'una serie de reaccions a la cadena de citocroms que es troba en la membrana interna de l'organel.la. La font d'energia necessaria per aquesta sintesi s'obte en les cel.lules animals dels nutrients de l'ingestio, i de la llum solar en les plantes. Existeix una via alternativa de sintesi d'ATP extramitocondrial, la glicolisi, que s'inicia amb la fosforilacio de la glucosa per l'enzim hexokinasa.
Interaccio llum-materia
L'energia electromagnetica l'ona de la qual oscil.la en una longitud d'ona de nanometres es anomenada llum. En aquestes frequencies, l'energia promou excitacio electronica de certs atoms i molecules. Existeix una interaccio diferent de la llum amb molecules, produida per el camp electromagnetic que per definicio la llum provoca en qualsevol medi. El camp electric resultant desplaca els electrons dels enllacos quimics produint una polaritzacio del medi sense que existeixi absorcio de l'energia. Aquest es un mecanisme interactiu que existeix sempre, i es l'unic que es dona en molecules que son transparents (no absorbeixen) per a una determinada frequencia de la llum, com es el cas de l'ATP per l'energia visible i infravermella propera.
Experiments, resultats i discussio
Quan l'ATP es excitat amb fotons ultraviolats, es produiex una fluorescencia en longituts d'ona visibles. L'io magnesi s'ha utilitzat per estudiar com la llum visible i infravermella propera produiex un desplacament de carregues electriques a la molecula d'ATP.
La construccio d'un interferometre de Michelson ha servit per observar l'interaccio no absortiva de la llum i l'ATP. La mesura directa de l'index de refraccio d'una solucio d'ATP dona informacio sobre les caracteristiques electriques del medi. L'observacio de que aquest index canvia despres d'irradiar la solucio amb longituds d'ona visibles i infravermelles properes, confirmen que la llum provoca canvis electrics significatius en l'ATP.
En aquest treball tambe s'ha estudiat el comportament bioquimic de l'ATP irradiat quant forma part de dues reaccions quimiques diferents: la de la luciferina-luciferasa i la de la hexoquinasa. En tots dos casos, l'us d'aquest ATP irradiat ha produit una alteracio dels parametres cinetics estudiats, V0 i k en la reaccio de la luciferina-luciferasa, i km i vmax en la reaccio de l'hexoquinasa.
Conclusions
Aquesta interaccio no absortiva de la llum amb l'ATP es la primera descrita per a una biomolecula. El mecanisme aporta noves dades per explicar els efectes observats en el metabolisme cel.lular despres de l'irradiacio d'organismes, teixits i cultius cel.lulars amb llum visible i infravermella propera.
ATP is a key molecule in cellular metabolism. In this thesis, I examined the effects of visible (635 and 655 nm) and near-infrared (810 and 830 nm) light on ATP in solution. I also examined were the biochemical behavior of light-exposed ATP in the luciferine-luciferase reaction and hexokinase reaction, the initial step in glycolysis that begins extra mithocondrial ATP synthesis. Irradiated groups in the luciferine-luciferase reaction showed an improvement in the kinetic parameters V0 and k, and more ATP molecules reacted with the enzyme when they were excited by light. When irradiated ATP was added to the hexokinase reaction, the experimental groups showed significant differences in the Michaelis-Menten kinetic parameters (km for ATP and vmax) and the rate of product synthesis was greater. Changes in both reactions were wavelength and dose dependant.
When ATP was excited with UV photons, it fluoresced. This fluorescence decreased when Mg2+ was added, probably because the ion binds the phosphates, which are the part of the molecule responsible for light emission. Irradiating the ATP-Mg2+ solution with 655 nm and 830 nm light increased the fluorescence resulting from a displacement of charges in the phosphor-oxygen bond that repels Mg2+.
The refraction of light in an ATP solution was observed by the Michelson interferometer and by directly measuring the refractive index. The refractive index changed after red and near-infrared light interaction due to a change in the electrical permittivity of the medium.
Since ATP in water is transparent to visible and near-infrared light, and is therefore not a chromophore for those wavelengths, I conclude that the observed light interaction with ATP is not due to photon absorption but to the electromagnetic disturbance produced by the light, which leads to a polarization of the dielectric molecule that is ATP.
This interaction of visible and near-infrared electromagnetic energy with ATP offers new perspectives for explaining light interaction at subcellular level.

In this thesis, improvement of face recognition performance with the use of images from the visible (VIS) and near-infrared (NIR) spectrum is attempted. Face recog- nition systems can be adversely affected by scenarios which encounter a significant amount of illumination variation across images of the same subject. Cross-spectral face recognition systems using images collected across the VIS and NIR spectrum can counter the ill-effects of illumination variation by standardising both sets of images. A novel preprocessing technique is proposed, which attempts the transformation of faces across both modalities to a feature space with enhanced correlation. Direct matching across the modalities is not possible due to the inherent spectral dif- ferences between NIR and VIS face images. Compared to a VIS light source, NIR radiation has a greater penetrative depth when incident on human skin. This fact, in addition to the greater number of scattering interactions within the skin by rays . from the NIR spectrum can alter the morphology of the human face enough to dis- able a direct match with the corresponding VIS face. Several ways to bridge the gap between NIR-VIS faces have been proposed previously. Mostly of a data-driven ap- proach, these techniques include standardised photometric normalisation techniques and subspace projections. A generative approach driven by a true physical model has not been investigated till now. In this thesis, it is proposed that a large proportion of the scattering interactions present in the NIR spectrum can be accounted for using a model for subsurface scattering. A novel subsurface scattering inversion (SSI) algorithm is developed that implements an inversion approach based on translucent surface rendering by the computer graph- ics field, whereby the reversal of the first order effects of subsurface scattering is attempted. The SSI algorithm is then evaluated against several preprocessing tech- niques, and using various permutations of feature extraction and subspace projection algorithms. The results of this evaluation show an improvement in cross spectral face recognition performance using SSI over existing Retinex-based approaches. The top performing combination of an existing photometric normalisation technique, Sequential Chain, is seen to be the best performing with a Rank 1 recognition rate of 92.5%. In addition, the improvement in performance using non-linear projection models shows an element of non-linearity exists in the relationship between NIR and VIS.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 137-160).
We investigate how the external quantum efficiency (EQE) of colloidal quantum-dot light emitting devices (QD-LEDs) can be enhanced by addressing in situ QD photoluminescence (PL) quenching mechanisms occurring with and without applied bias. QD-LEDs promise efficient, high colour-quality solid-state lighting and displays, and our cost analysis of industrial-scale QD synthesis suggests they can be cost competitive. Efficiency 'roll-off' at high biases is among the most enduring challenges facing all LED technologies today. It stands in the way of high efficiencies at high brightness, yet it has not previously been studied in QD-LEDs. Simultaneous measurements of QD electroluminescence (EL) and PL in an operating device allow us to show for the first time that EQE roll-off in QD-LEDs derives from the QD layer itself, and that it is entirely due to a bias-driven reduction in QD PL quantum yield. Using the quantum confined Stark Effect as a signature of local electric fields in our devices, the bias-dependence of EQE is predicted and found to be in excellent agreement with the roll-off observed. We therefore conclude that electric field-induced QD PL quenching fully accounts for roll-off in our QD-LEDs. To investigate zero-bias PL quenching, we fabricate a novel near-infrared (NIR)-emitting device based on core-shell PbS-CdS QDs synthesised via cation exchange. QDs boast high PL quantum yield at wavelengths beyond 1 [mu]m, making them uniquely suited to NIR applications such as optical telecommunications and computing, bio-medical imaging, and on-chip bio(sensing) and spectroscopy. Core-shell PbS-CdS QDs enhance the peak EQE of core-only PbS control devices by 50- to 100-fold, up to 4.3 %. This is more than double the efficiency of previous NIR QD-LEDs, making it the most efficient thin-film NIR light source reported. PL measurements reveal that the efficiency enhancement is due to passivation of the PbS core by the CdS shell against a non-radiative recombination pathway caused by a neighboring conductive layer within the device architecture.
by Geoffrey James Sasajima Supran.
Ph. D.

Soil analysis for agriculture, pollution assessment/remediation or resource exploration requires rapid procedures that are reliable, fast and cheap. This study examined the potential of visible near infrared diffuse reflectance spectroscopy (VNIR DRS) for soil analysis with emphasis on soil organic carbon (SOC) and extractible total petroleum hydrocarbon (ETPH). Preliminary laboratory studies were conducted to determine if visible near infrared diffuse reflectance spectral data contain adequate information for characterising SOC and ETPH and to identify sensitive wavelength regions best suited for quantitative modeling. It was concluded that VNIR DR spectra contained adequate information to quantify both SOC and ETPH in soils. Modelling with the whole spectrum was also found to give better predictions compared to modelling with portions of the spectrum. A 76/24 dataset split pattern was identified as an optimal split, ensuring that significant proportions of datasets are used for both model calibration and testing. Soil is inherently heterogeneous varying in space. The prediction performances of VNIR DRS models were observed to reduce with an increase in the geographical size of soil collection sites indicating that the best calibration models will likely be generated from spectral data derived from local soils with similar geology. Performance of VNIR DRS for characterizing ETPH was affected by SOC content. Higher model performances were observed at low organic carbon content, though all models developed for the SOC range studied (0.94 – 26.5%) had good prediction qualities (RPD > 2). Similarly, model performances were also affected by the type of petroleum hydrocarbon product that had been used to contaminate soils. This study provides evidence that VNIR DRS can be an important analytical approach to soil analysis particularly when and where costs and time are limiting conditions.

L'exoplanètologie commence à s’intéresser aux naines M afin de détecter et caractériser des planètes. Ces étoiles sont les plus communes; leur petite taille facilite la détection de petites planètes; et les planètes dans la zone habitable sont plus faciles à détecter grâce à leur proximité à l'étoile. La population émergente de planètes de naines M montre des caractéristiques intrigantes par rapport à celle des étoiles FGK. Cette thèse a pour but explorer la détection de planètes de naines M par vitesses radiales visibles et proche infrarouges. J'ai aussi analysé la population de planètes de naines M au début et fin de la thèse. Dans le visible, j'ai travaillé avec le spectrographe SOPHIE (OHP), en tant que membre du consortium SOPHIE exoplanètes qui mène des programmes de recherche d'exoplanètes, dont l'un d'eux cherche des planètes autour de naines M. J'ai adapté un algorithme de calcul des vitesses radiales à ses cibles et analysé les données résultantes. J'ai confirmé la présence de signaux périodiques qui, bien que présents dans l'analyse standard, étaient partiellement noyés dans le bruit. Quatre nouvelles planètes ont été publiées. J'ai étudié des indices d'activité stellaire en identifiant les plus adaptés pour SOPHIE. Dans le proche infrarouge, j'ai travaillé avec le spectropolarimètre SPIRou (CFHT). Ce nouvel instrument est conçu pour observer des naines M, qu'irradient principalement dans l'infrarouge. J'ai travaillé sur le système de réduction des données, particulièrement sur la solution en longueur d'onde, crucial pour mesurer des vitesses radiales précises. J'ai développé et testé plusieurs méthodes pour combiner les différentes sources de calibration
Exoplanet science has begun to focus on M-dwarf stars for exoplanet detection and characterisation. They are the most common stars in the galaxy; their small size means smaller exoplanets can be detected; habitable zone planets are easier to detect as it is closer to the star. The emerging population of M dwarf planets shows intriguing characteristics compared to those hosted by FGK stars. The aim of this thesis is to explore the detection of exoplanets around M dwarfs via the radial velocity method, in both the near infra-red and visible domains. I also performed analyses of the known population of planets around M dwarfs at the start of the thesis and at its conclusion. In the visible, I worked with the SOPHIE spectrograph at the OHP, as part of the SOPHIE exoplanets consortium. This group leads several exoplanet surveys, one of which searches for planets around M dwarfs. I adapted a template-matching algorithm to its targets, and analysed the resulting radial velocities. I confirmed the significance of periodic signals that, while apparent in the standard analysis, were partially hidden by noise. Four new exoplanets have been published. I studied stellar activity indicators, identifying those most suited to SOPHIE spectra. In the near infrared, I worked with the SPIRou spectropolarimeter at the CFHT. This new instrument was conceived for observing M dwarfs, which emit most of their radiation in the infrared. I worked on the data reduction pipeline, specifically on the wavelength solution (pixel position-wavelength correspondence), crucial for measuring precise radial velocities. I developed and tested ways to combine different wavelength calibrators

A new technique for detecting solar oscillations in the visible to near infrared continuum has been developed and tested at the Santa Catalina Laboratory for Experimental Relativity by Astrometry (SCLERA). In 1985, measurements of the solar radiation intensity near disk center were made by Oglesby (1986, 1987). The results of these observations have been compared to the reported detections and classifications by Hill (1984, 1985) and Rabaey and Hill (1987) of the low-order, low-degree acoustic modes; the intermediate degree f-modes; and the low-order g-modes. For the low-order, low-degree, acoustic modes and the intermediate degree f-modes, a total of 40 multiplets were used in the analysis. The coincidence rates between the peaks in the power spectrum of the 1985 observations and the classified frequency spectrum for multiplets taken in subgroups of ≈5 (same n and contiguous in ℓ) are typically 4-5 σ above the accidental coincidence rate. The maximum coincidence rates for these same subgroups of multiplets were found to occur for frequency shifts of the classified spectrum ranging from -0.27 μHz for modes that are sensitive to the internal properties near the bottom of the convection zone to 0.06 μHz for modes that are sensitive to internal properties near the top of the convection zone. Also included in this work is a comparison of diameter measurements obtained at SCLERA in 1978 (Caudell 1980) with the classified modes mentioned above. Agreement in this case is at the 3.1 σ level for both the f-mode (n = 0) multiplets with 21 ≤ ℓ ≤ 36 and the n = 1, 6 ≤ ℓ ≤ 12 acoustic modes. The confirmation of the detection and classification of the low-order g-modes of oscillation was found to be at the 3.3 σ level. Additionally, the m dependence of the 1985 power spectrum was found to behave in the manner expected for the proper classifications in m for the g-modes.

Hydrovolcanic basaltic tephras from tuff rings and tuff cones were studied in order to better understand their origin and alteration processes. The visual and near infrared reflectance of tephras collected from Basin and Range tuff rings and tuff cones was measured in the laboratory. Further mineralogic and chemical information was gained through petrographic microscopy, X-ray diffraction, electron microprobe analysis and iron Mossbauer spectrometry. In addition, remotely sensed data from several airborne sensors was obtained for the Lunar Crater Volcanic Field in Nye County, Nevada and the Pavant Butte tuff cone in Millard County, Utah. Fresh tuff rings, resulting from dry pyroclastic surges, are composed of a variable mix of country rock fragments and unaltered sideromelane which has a dark reflectance spectrum dominated by Fe²⁺ crystal field bands near 1 and 2 μm. If water condenses on the sideromelane, a process of nearly syn-depositional hydration can occur. With increasing hydration, water and OH vibrational absorptions develop at 1.4 and 1.9 μm. Smectite clay minerals were recognized within thinly bedded tuff rings by the presence of a 2.2 μm absorption and by XRD results. These minerals have developed without extensive palgonitization. Tuff ring tephras can also become oxidized to the extent that a well developed Fe³⁺-O²⁻ charge transfer edge develops with weak Fe³⁺ crystal field features shortwards of 0.8 μm. The poorly inflated pyroclastic “flow”, that characterizes tuff cone formation, produces hot, wet, cohesive ash deposits that can alter relatively rapidly to palagonite. The reflectance of these highly palagonitized tephras is twice as high as that of tuff ring deposits, H₂O and OH vibrational absorption bands are also stronger and a 2.3 μm Mg-OH band is generally present. Increasing oxidation causes spectral features resulting from Fe³⁺ to become more pronounced. These include a shortwards shift in position and shallowing of the “1-μm” crystal field band and steepening of the Fe³⁺-O²⁻ charge transfer edge. Differences in spectral reflectance are ascribed primarily to differences in the degree of alteration which in turn is influenced by the water/magma ratio extant at the time of eruption. Remotely sensed data of hydrovolcanic vents acquired by several different air- and spaceborne sensors was also examined. These data sets were analyzed using a linear spectral mixture model. It was found that palagonite tuff constitutes an easily mapped spectral endmember, while the hydrated tuff typical of tuff rings is difficult to distinguish from other dark materials. The best mapping was performed with the systems with high spatial resolution such as the NSOO1 Thematic Mapper Simulator and the Geoscan Mk II advanced multispectral scanner. Airborne Visible/lnfrared Imaging Spectrometer (AVIRIS) data, calibrated to reflectance through reference endmember modelling, revealed previously undetected 2.2 μm absorption features in the palagonite tuff at Pavant Butte. The 1-μm feature in Pavant Butte palagonite tuff was mapped from the AVIRIS data using a band depth mapping routine although the resulting discrimination of palagonite tuffs was not as good as was obtained with the spectral mixture model.

This work presents recent advances in photorefractive polymer composites towards improved efficiency, speed, persistence of holograms and sensitivity at both visible and near infrared wavelengths. Besides the pure performance characteristics, a thin-device approach is presented to reduce operating voltage of these devices to practical levels and these materials are analyzed in both reflection and transmission geometries.The thin device operating at 1.3kV holds erasable, Bragg holograms with 80% efficiency in addition to its video-rate response time. The transition of hologram state from 'thick' to 'thin' is analyzed in detail. On the near IR portion of spectrum, new photorefractive polymer composites have been developed that enable high performance operation at 845nm and 975nm. Utilizing our novel photorefractive materials we demonstrate large diffraction efficiency in four-wave mixing experiments and video-rate response times. A major step towards achieving submillisecond response times is obtained through recording photorefractive gratings with individual nanosecond pulses at 532nm. At 4 mJ/cm2 illumination, a maximum diffraction efficiency of 56% has been obtained with a build-up time of only 300 microseconds (t1). This fast response enables applications in optical processing requiring frame rates of 100Hz or more. Due to the short duration of the writing pulses, the recording is insensitive to vibrations. Combining molecules that have different frontier orbital energies in a copolymer system and utilizing thermal fixing approach has led to long grating lifetimes of more than several hours. Later, in this dissertation, two low-glass-transition photorefractive polymer composites are investigated in reflection geometry. 60% is diffraction efficiency is observed in 105 micron thick devices of a PVK based composite. The reflection holograms are more sensitive to reading angle and slight birefringence due to the poling of chromophores has proven to cause a Bragg mismatch.

Abstract The present thesis exposes methods and results obtained exploiting information provided by visible and near-infrared spectra over Mercury and Venus. We use information from different datasets to perform a geologically supervised investigation, in order to identify the presence of compositional heterogeneities and reconstruct the stratigraphy in the shallow crust of the two Terrestrial planets. We name these procedures “Datasets Fusion Techniques” (DFTs). We combine the MASCS dataset with the MDIS dataset from the MESSENGER mission to analyze the local and global crustal properties of Mercury. We select all MASCS observations contained within geologic units previously mapped using high-resolution MDIS NAC images. Similarly, we combine the Venus Express VIRTIS dataset with Magellan SAR imaging dataset for identifying location and extent of the recently active lava flows possibly responsible for the relatively high 1 μm emissivity anomalies observed by the VIRTIS instrument on Idunn Mons on Venus. Using a forward modeling-like procedure, we mapped a number of lava flows on Magellan SAR images, then assigning them a different value of simulated emissivity at each iteration. We found one non-unique solution which well approximates VIRTIS observations. This thesis is a comprehensive study which embraces three main research works performed during the current PhD project. The results show the occurrence of vertical and horizontal heterogeneities in the composition of the shallow crust of Mercury, providing as well important indications for the presence of N-S dichotomy. We also found that the recently active lava flows on Idunn Mons are most likely flank flows located on the eastern flank of the volcanic structure. We could finally reconstruct the stratigraphy beneath the local scale study areas of Mercury and Venus. This PhD thesis demonstrates that DFTs can be used as a powerful expedient for improving the quality of information we can achieve from remote sensing analyses
Original papers Piero D’Incecco, Jörn Helbert, Mario D’Amore, Alessandro Maturilli, James W. Head, Rachel L. Klima, Noam R. Izenberg, William E. McClintock, Harald Hiesinger, Sabrina Ferrari, Shallow crustal composition of Mercury as revealed by spectral properties and geological units of two impact craters, Planetary and Space Science, Volume 119, 15 December 2015, Pages 250-263, ISSN 0032-0633, http://dx.doi.org/10.1016/j.pss.2015.10.007. (http://www.sciencedirect.com/science/article/pii/S0032063315003062) Keywords: Mercury; MESSENGER; MASCS; MDIS; Impact craters; Stratigraphy Piero D’Incecco, Jörn Helbert, Mario D’Amore, Sabrina Ferrari, James W. Head, Alessandro Maturilli, Harald Hiesinger, A geologically supervised spectral analysis of 121 globally distributed impact craters as a tool for identifying vertical and horizontal heterogeneities in the composition of the shallow crust of Mercury, Planetary and Space Science, Volume 132, 1 November 2016, Pages 32-56, ISSN 0032-0633, http://dx.doi.org/10.1016/j.pss.2016.08.004. (http://www.sciencedirect.com/science/article/pii/S0032063315301094) Keywords: Mercury; MESSENGER; MASCS; MDIS; Impact craters; Datasets Fusion Techniques (DFTs) Piero D'Incecco, Nils Müller, Jörn Helbert, Mario D'Amore, Idunn Mons on Venus: Location and extent of recently active lava flows, Planetary and Space Science, Volume 136, February 2017, Pages 25-33, ISSN 0032-0633, http://dx.doi.org/10.1016/j.pss.2016.12.002. (http://www.sciencedirect.com/science/article/pii/S003206331630112X) Keywords: Venus; VIRTIS; Magellan; Volcanism; Idunn Mons; Stratigraphy

Image fusion is a method in which all the relevant information is collected from the input source images and included in few/single output image. Image fusion techniques are divided into two broad categories: spatial domain and transform domain. Principal component analysis (PCA) is a spatial domain technique which is computationally simpler and reduces redundant information but has the demerit of spectral degradation. Lifting wavelet transform (LWT) is a transform domain technique which has an adaptive design and demands less memory. In this project, a novel hybrid fusion algorithm has been introduced which combines the LWT and PCA in a parallel manner. These two fusion methods are applied on Infrared and Visible image data set. Infrared and visible images contain complementary information and their fusion gives us an output image which is more informative than the individual source images. The hybrid method is also compared with conventional fusion techniques like PCA, LWT and DWT. It has been shown that the proposed method outperforms the conventional methods. The results are analyzed using performance parameters standard deviation, average value, the average difference, and normalized cross- correlation.

This thesis presents the development of a new class of high-power, continuous-wave (cw) optical parametric oscillators (OPOs) with extended tunability from visible to near-infrared (near-IR). While lasers have been in use for nearly 50 years, it is still difficult to develop laser systems that can cover many regions of the optical spectrum, from ultraviolet (UV) and visible to the near and mid-infrared wavelength range, with potential applications in the fields such as spectroscopy, remote sensing, trace gas detection, and many more. Development of cw OPOs in singly-resonant oscillator (SRO) configurations, the focus of this thesis, is challenging due to the high threshold pump power (several watts). In addition, with visible pumping, photorefractive effect and thermal lensing effects become important issues to overcome. Therefore, the realization of practical cw SROs requires optimal cavity design, suitable nonlinear materials, and high-power laser with high spectral and spatial quality. High-power, single-frequency, cw SROs based on 30-mm-long MgO-doped, stoichiometrically grown, periodically-poled LiTaO3 (MgO:sPPLT) have been developed. The oscillators were pumped in the green by a frequency-doubled cw diode-pumped Nd:YVO4 laser at 532 nm. With a single grating period of 7.97 µm, continuous signal and idler coverage over 848-1430 nm is obtained by temperature tuning between 52 oC and 248 oC. In a linear cavity configuration and double-pass pumping, an oscillation threshold of 2.88 W has been obtained, and single-pass idler powers in excess of 1.51 W have been generated over 1104-1430 nm for 6 W of pump power at an extraction efficiency of 25.2% and photon conversion efficiency of 56.7%. For single-frequency performance of the cw SRO across 848-1430 nm, we have used a compact ring cavity configuration along with a frequency selecting element (etalon). Using the same MgO:sPPLT crystal, the SRO oscillation threshold of 2.84 W has been obtained, and single-pass idler powers in excess of 1.59 W have been generated over 1104-1430 nm with a maximum SRO extraction efficiency of 25.2% and pump depletions as much as 67%. The single-frequency idler output has a linewidth of ~7 MHz. Under free-running conditions and in the absence of thermal isolation, the idler power exhibits a peak-to-peak stability of 16% over 5 hours. Although the cw SRO can provide optical radiation across 848-1430 nm, the high output power was only available over 1104-1430 nm, due to the high reflectivity of the cavity mirrors for SRO operation. Using finite output coupling of the resonant wave, we have extended the available practical output power across the entire tuning range. The cw out-coupled SRO (OC-SRO) can deliver total power of up to 3.6 W at 40% extraction efficiency with a linewidth of 3 MHz across 848-1430 nm. The signal power shows a peak-to-peak power stability <10.7% over 40 minutes in a TEM00 spatial mode with M2 <1.52. Without any active stabilization, the resonant signal exhibits a natural long-term frequency stability <75 MHz over 15 minutes and short-term frequency stability <10 MHz over 10 seconds, demonstrating the potential of the system for spectroscopic applications. Using internal second-harmonic-generation of the resonant near-infrared signal radiation of the MgO:sPPLT cw SRO in a 5-mm-long BiB3O6 crystal, we have generated 1.27 W of cw, single-frequency blue power over a tunable range of 425-489 nm with a linewidth of 8.5 MHz and a Gaussian spatial beam profile. The blue source is frequency-stable to better than 280 MHz, limited by the resolution of the wavemeter. We have also developed cw green sources, in a simple single-pass experimental configuration by frequency-doubling a fiber laser using MgO:sPPLT and periodically-poled KTiOPO4 (PPKTP) crystals, generating as much as 9.6 W of green radiation in TEM00 spatial beam profile (M2 <1.33) with a single-pass efficiency of 32.7% in MgO:sPPLT. This green source has also successfully been used to pump cw SROs and will be used to pump Ti:sapphire lasers. Using this frequency-doubled green source, we have demonstrated cw OC-SRO providing a stable single-frequency output power up to 2 W across the tuning range of 855-1408 nm, with peak-to-peak power stability <11.7%, frequency-stability <10 MHz over 10 seconds, in TEM00 (M2 <1.26) spatial beam profile.
Esta tesis presenta el desarrollo de una nueva clase de osciladores ópticos paramétricos (OPOs) de onda continua (cw) y alta potencia con extendida sintonización desde el visible al infrarrojo (IR) cercano. A pesar de que los láseres están en uso desde hace casi 50 años, todavía es difícil desarrollar sistemas láser que puedan cubrir muchas regiones del espectro óptico en los rangos de longitud de onda desde el ultravioleta (UV) y visible hasta el infrarrojo cercano y medio, con potenciales aplicaciones en campos como la espectroscopia, sensores remotos, detección de trazas de gases, entre muchas otras. El desarrollo de cw OPOs en configuraciones de oscilador simplemente resonante (SRO), objetivo principal de esta tesis, es un gran desafío debido al alto umbral de potencia de bombeo (varios watts). Además, cuando se emplea bombeo visible, los efectos fotorrefractivo y de lente térmica adquieren especial relevancia y son difíciles de superar. Por lo tanto, la realización de cw SROs prácticos requiere de un óptimo diseño de cavidad, adecuados materiales no lineales y láseres de alta potencia con excelente calidad tanto espectral como espacial. Se han desarrollado cw SROs de alta potencia y frecuencia única basados en cristales de LiTaO3 de 30 mm de longitud, de crecido estequiométrico, con dopado de MgO y periódicamente pulidos (MgO:sPPLT). Los osciladores fueron bombeados en el verde mediante el láser de cw Nd:YVO4 bombeado por diodos y doblado en frecuencia. Utilizando un único periodo de red de 7.97 m, se ha obtenido cobertura continua de los campos señal y pivote en el rango 848-1430 nm por sintonización de temperatura entre 52ºC y 248ºC. Empleando una configuración de cavidad lineal y bombeo de doble paso, se ha logrado un umbral de oscilación de 2.88 W y se han generado potencias superiores a 1.51 W para el campo pivote en simple paso dentro del rango 1104-1430 nm para 6 W de potencia de bombeo, eficiencia de extracción del 25.2% y eficiencia de conversión de fotón del 56.7%. Con el objetivo de operar el cw SRO en frecuencia única a través del rango 848-1430 nm, hemos utilizado una configuración compacta de cavidad en anillo junto a un elemento para la selección de frecuencia (etalon). Utilizando el mismo cristal de MgO:sPPLT, se ha obtenido un umbral de oscilación del SRO de 2.84 W y se han generado potencias superiores a 1.59 W para el campo pivote en paso único dentro del rango 1104-1430 nm con una eficiencia máxima de extracción del 25.2 % y agotamiento del bombeo tan alto como el 67%. La salida del campo pivote en frecuencia única tiene un ancho de línea de ~ 7 MHz. Bajo condiciones de sistema libre y en ausencia de aislamiento térmico, la potencia del campo pivote exhibe estabilidad de pico a pico de 16% durante 5 horas. A pesar de que el cw SRO puede proveer radiación óptica en el rango 848-1430 nm, la alta potencia de salida solo se consiguió obtener en el rango 1104-1430 nm a causa de la alta reflectividad de los espejos de la cavidad para operar en SRO. Utilizando un acoplamiento de salida finito de la onda resonante, hemos extendido la disponibilidad de prácticas potencias de salida a través de todo el rango de sintonía. El cw SRO con acoplador de salida (OC-SRO) puede entregar un apotencia total de hasta 3.6 W con una eficiencia de extracción del 40% y con un ancho de línea de 3 MHz en el rango 848-1430 nm. La potencia del campo señal muestra fluctuaciones en potencia de pico a pico <10.7% durante 40 minutos y modo espacial TEM00 con M2<1.52. En ausencia de estabilización activa, el campo señal resonante exhibe una estabilidad en frecuencia natural a largo término con fluctuaciones <75 MHz durante 15 minutos, así como a corto término con fluctuaciones<10MHz durante 10 segundos, demostrando el potencial del sistema para aplicaciones en espectroscopia. Utilizando generación interna de segundo harmónico del campo señal resonante en el rango del infrarrojo cercano del MgO:sPPLT cw SRO mediante un cristal de BiB3O6 de 5 mm de longitud, hemos logrado generar 1.27 W de potencia cw y frecuencia única en el azul dentro del rango de sintonía 425-489 nm y con un ancho de línea de 8.5 MHz y un perfil espacial del haz de tipo Gaussiano. La estabilidad en frecuencia de la fuente azul es mejor que 280 MHz, donde la limitación viene impuesta por la resolución del medidor de longitud de onda empleado. Adicionalmente, hemos desarrollado fuentes verdes en cw en una sencilla configuración experimental de único paso, mediante el doblado en frecuencia de un láser de fibra con cristales de MgO:sPPLT y KTiOPO4 pulido periódicamente (PPKTP), generando hasta 9.6 W de radiación verde en modo espacial TEM00 (M2<1.33) con una eficiencia de paso único de 32.7% en MgO:sPPLT. Esta fuente verde has sido también empleada exitosamente para bombear cw SROs y será utilizada para bombear láseres de Ti:sapphire. Mediante esta fuente verde doblada en frecuencia, hemos demostrado que el cw OC-SRO proporciona una salida estable en frecuencia única con potencia de hasta 2 W a través del rango de sintonía 855-1408 nm, con estabilidad en potencia de pico a pico <11.7%, estabilidad en frecuencia <10 MHZ durante 10 segundos y modo espacial TEM00 (M2<1.26).

Després del descobriment dels primers exoplanetes fa unes tres dècades, la detecció i caracterització de companys planetaris s’ha convertit en un tema de recerca prominent, especialment la cerca de planetes semblants a la Terra, cossos rocosos que orbiten a la zona habitable (HZ) de les seves estrelles hostes. Un dels principals mètodes utilitzats per trobar i caracteritzar exoplanetes és la tècnica de l’espectroscòpia Doppler o velocitat radial (RV), basada en l’ús d’espectres estel·lars per mesurar canvis periòdics en la RV d’una estrella causats per l’atracció gravitatòria d’un exoplaneta en òrbita. Actualment, la variabilitat intrínseca de les estrelles hostes és el principal repte en l’estudi d’exoplanetes. Les estrelles no són cossos invariables i homogenis, sinó que presenten variabilitat en diferents escales de temps. La més rellevant és l’activitat magnètica estel·lar, que inclou fenòmens com ara taques o fàcules que apareixen a la superfície de l’estrella i estan modulades per la seva rotació. Aquests fenòmens distorsionen els espectres estel·lars, introduint biaixos en les RVs prou grans com per amagar o fins i tot imitar el senyal causat per un planeta. Per tant, per continuar detectant i estudiant exoplanetes de baixa massa, és clau aconseguir una millor comprensió d’aquests fenòmens estel·lars i els seus efectes en les nostres observacions. Aquesta tesi se centra en l’estudi dels efectes de l’activitat estel·lar en observacions espectroscòpiques d’estrelles fredes obtingudes amb l’instrument CARMENES. CARMENES és un espectrògraf d’alta resolució capaç d’observar el rang de longitud d’ona visible i infraroig proper. Està realitzant un estudi de més de 300 nanes M, les estrelles amb menor massa de la seqüència principal, amb l’objectiu primordial de detectar exoplanetes petits. En primer lloc, hem desenvolupat un codi que implementa el mètode de la funció de correlació creuada (CCF) per mesurar RVs i indicadors d’activitat estel·lar en observacions d’alta resolució, i l’hem aplicat a les dades de CARMENES. Aquest mètode utilitza màscares binàries ponderades, un template estel·lar simplificat construït mitjançant la selecció de línies espectrals. Hem creat diverses màscares en funció del subtipus espectral i de la velocitat de rotació de l’estrella a analitzar. A continuació, hem utilitzat els indicadors d’activitat derivats de la CCF, juntament amb altres indicadors d’activitat espectroscòpics, per analitzar les seves variacions temporals en una mostra de quasi 100 nanes M de diverses masses i nivells d’activitat. Aproximadament la meitat de les estrelles analitzades mostren RVs amb senyals d’activitat clars. Diferents indicadors són sensibles a l’activitat de manera diferent segons les característiques de l’estrella: indicadors cromosfèrics són més útils per a estrelles de baixa activitat, indicadors relacionats amb el canvi de RV amb longitud d’ona funcionen millor per a les estrelles més actives, i altres indicadors relacionats amb el canvi d’amplada de les línies fotosfèriques proporcionen resultats similars en tot tipus d’estrelles, però són especialment útils per a les més actives i de menor massa. Finalment, hem analitzat els efectes de l’activitat sobre línies d’absorció individuals presents en l’espectre d’estrelles actives. Estudiant les correlacions entre les RVs de línies individuals i els indicadors d’activitat, podem classificar les línies observades segons la seva sensibilitat a l’activitat. Això ens permet seleccionar línies afectades de forma diferent per l’activitat i utilitzar-les per tornar a calcular RVs. Així obtenim RVs per a les quals mitiguem o incrementem el senyal d’activitat en diversos graus. També observem que les mateixes línies en diferents estrelles mostren diferent sensibilitat a l’activitat.
Después del descubrimiento de los primeros exoplanetas hace unas tres décadas, la detección y caracterización de compañeros planetarios se ha convertido en un tema de investigación prominente, especialmente la búsqueda de planetas parecidos a la Tierra, cuerpos rocosos que orbitan en la zona habitable (HZ) de sus estrellas huéspedes. Uno de los principales métodos utilizados para encontrar y caracterizar exoplanetas es la técnica de la espectroscopía Doppler o velocidad radial (RV), basada en el uso de espectros estelares para medir cambios periódicos en la RV de una estrella causados por la atracción gravitatoria de un exoplaneta en órbita. Actualmente, la variabilidad intrínseca de las estrellas huéspedes es el principal reto en el estudio de exoplanetas. Las estrellas no son cuerpos invariables ni homogéneos, sino que presentan variabilidad en distintas escalas de tiempo. La más relevante es la actividad magnética estelar, que incluye fenómenos como manchas o fáculas que aparecen en la superficie de la estrella y están moduladas por su rotación. Estos fenómenos distorsionan los espectros estelares, introduciendo sesgos en las RVs suficientemente grandes como para esconder o hasta imitar la señal causada por un planeta. Por lo tanto, para continuar detectando y estudiando exoplanetas de baja masa, una mejor comprensión de estos fenómenos estelares y sus efectos en nuestras observaciones es clave. Esta tesis se centra en el estudio de los efectos de la actividad estelar en observaciones espectroscópicas de estrellas frías obtenidas con el instrumento CARMENES. CARMENES es un espectrógrafo de alta resolución capaz de observar en el rango de longitudes de onda visible e infrarojo cercano. Está realizando un estudio de más de 300 enanas M, las estrellas con menor masa de la secuencia principal, con el objetivo primordial de detectar exoplanetas pequeños. En primer lugar, hemos desarrollado un código que implementa el método de la función de correlación cruzada (CCF) para medir RVs e indicadores de actividad estelar en observaciones de alta resolución, y lo hemos aplicado a los datos de CARMENES. Este método usa máscaras binarias ponderadas, un template estelar simplificado construido seleccionando líneas espectrales. Hemos creado varias máscaras en función del subtipo espectral y de la velocidad de rotación de la estrella a analizar. A continuación, hemos utilizado los indicadores de actividad derivados de la CCF, juntamente con otros indicadores de actividad espectroscópicos, para analizar sus variaciones temporales en una muestra de casi 100 enanas M de varias masas y niveles de actividad. Aproximadamente la mitad de las estrellas analizadas muestran RVs con señales de actividad claros. Distintos indicadores son sensibles a la actividad de forma diferente según las características de la estrella: indicadores cromosféricos son más útiles para estrellas de baja actividad, indicadores relacionados con el cambio de RV con la longitud de onda funcionan mejor para estrellas más activas, y otros indicadores relacionados con el cambio de anchura de las líneas fotosféricas proporcionan resultados similares en todo tipo de estrellas, pero son especialmente útiles para las más activas y de menor masa. Finalmente, hemos analizado los efectos de la actividad sobre líneas de absorción individuales presentes en el espectro de estrellas activas. Estudiando las correlaciones entre las RVs de líneas individuales y los indicadores de actividad, podemos clasificar las líneas observadas según su sensibilidad a la actividad. Esto nos permite seleccionar líneas afectadas de forma distinta por la actividad y usarlas para volver a calcular RVs. De esta forma obtenemos RVs para las cuales mitigamos o incrementamos la señal de actividad en diversos grados. También observamos que las mismas líneas en distintas estrellas muestran diferente sensibilidad a la actividad.
After the discovery of the first exoplanets about three decades ago, the detection and characterization of planetary companions has become a prominent research topic, especially the search for Earth-like planets, rocky bodies orbiting in the habitable zone (HZ) of their host stars. One of the main methods used to find and characterise exoplanets is the Doppler spectroscopy or radial velocity (RV) technique, based on using stellar spectra to measure periodic changes in the RV of a star caused by the gravitational pull of an orbiting exoplanet. Currently, the intrinsic variability of the host stars is the major challenge faced in the study of exoplanets. Stars are not quiet, homogeneous bodies, but display variability on different timescales, the most concerning being stellar magnetic activity, phenomena such as spots or faculae appearing on the stellar surface and modulated by the stellar rotation. These features distort the stellar spectra, introducing biases in our RVs that can be large enough to hide or even mimic the signal caused by a planet. Therefore, to continue detecting and studying low-mass exoplanets, a better understanding of these stellar phenomena and their effects on our observations is key. This thesis is focused on the study of stellar activity effects on spectroscopic observations of cool stars obtained with the CARMENES instrument. CARMENES is a high-resolution spectrograph capable of observing on the visible and near-infrared wavelength ranges. It is performing a survey of over 300 M dwarfs, stars at the low-mass end of the main sequence, with the main goal of detecting small exoplanets. Firstly, we developed a pipeline that implements the cross-correlation function (CCF) method to measure RVs and indicators of stellar activity on high-resolution observations, and applied it to the CARMENES survey data. This method uses weighted binary masks, a simplified stellar template built by selecting sharp spectral lines, of which we created different kinds depending on the spectral subtype and the rotational velocity of the target star. We then used the activity indicators derived from the CCF, together with other spectroscopic activity proxies, to analyse their temporal variations in a sample of almost 100 M dwarfs with a range of masses and activity levels. We found that about half of the stars analysed show RVs with clear signals of activity. Different indicators trace activity differently depending on the characteristics of the star: chromospheric indicators are the most useful for low-activity stars, indicators related to the change in RV with wavelength work better for the most active stars, and other indicators related to the change in width of the photospheric lines provide similar results in all types of stars, but are especially useful for the most active and lowest-mass ones. Finally, we analysed the effects of activity on individual absorption features present on the spectra of active stars. By studying the correlations between the individual line RVs and activity indicators, we are able to classify the observed lines according to their sensitivity to activity. This allow us to select differently affected lines and use them to recompute RVs for which we mitigate or enhance the activity signal to varying degrees. We also observe that the same lines on different stars show different sensitivities to activity.

In this thesis, the electromagnetic spectra of both conducting and non-conducting particles are studied. The relationship between particle shape and spectra is explored through both modeling and experiments. Depending on the situation, spectra are modeled using techniques such as the discrete dipole approximation, the vibrational exciton model, various electrostatic methods, or density functional theory. These results are used to not only characterize the particles in the system of interest, but also understand how particle architecture influences its spectrum. Furthermore, it is demonstrated how the consideration of a particle's symmetry, and when appropriate the symmetry of the crystal structure that forms a particle, can greatly simplify the interpretation of spectra. The main systems studied in this work are Au nanoparticles and molecular aerosol particles composed of either pure C₂H₂, pure CO₂, mixtures of pure C₂H₂ and pure CO₂ or co-crystalline CO₂·C₂H₂. The molecular aerosol particles that are studied here were chosen due to their relevance to many planetary atmospheres. Several questions concerning the phase and shape of these molecular particles are addressed and answered. Finally, the similarities between the electromagnetic response of conducting and non-conducting particles are discussed at several points in this thesis. Hybridization schemes are shown to be a powerful tool for understanding the spectra of complex nanostructures. These schemes involve decomposing complex structures into primitive components. Spectra can then be understood as mixtures of the spectra of these primitive components. For the first time a formalism is developed that allows for such hybridization methods to be extended to non-conducting particles.

The UV-visible absorption spectrum of carbon vapor trapped in solid argon at low temperature contains many intense features, but only those of C₂ and C₃ have been identified. For this work, graphite vapor was produced under high vacuum conditions and condensed with argon onto a cold (∼10K) substrate. The resulting matrix-isolated carbon molecules were analyzed with both UV-visible and infrared absorption spectroscopy. Slight warming of the sample allowed formation of larger molecules and subsequent spectra traced the growth of their absorption features. The experiment associated infrared features to particular UV-visible features via their growth curves. The most reliable correlations are listed below. Theoretical calculations of equilibrium geometries and IR vibrational frequencies were performed on linear and nearly linear carbon chain molecules from C₃ to C₉ at the HF/SCF level of theory and from C₃ to C₇ at the MP2 level of theory, both using the 6-31G* basis set. Tentative assignment of the UV-visible features to molecules was made based on these considerations and on the following: the experimental IR/UV-visible correlations, previous experimental IR work, and modeling of the growth of the UV-visible features during matrix annealing. (UNFORMATTED TABLE FOLLOWS:) Molecule, UV-visible Feature (Å), IR Feature (cm⁻¹), Correlation Coefficient. C₃ (linear), 4100, 2040, .98. C₈ (linear), 3075, 1998, .97. C₈ (cyclic), 3900, 1804, .90. C₆ (linear), 2465, 1952, .86. C₇, 3480. C₉, 4480.

The performance of existing and planned millimeter and submillimeter astronomical arrays is limited by fluctuations in the amount of atmosperic water vapor along the atenna's line of sight. Correcting the resulting phase distortion of the received signals is seen as a significant technological challenge. Measurements of the variation in the line-of-sight water vapor abundance at the level of 1 micron precipitable water vapor on a time scale of 1 second and at arbitrary antenna positions are required. This thesis describes the design of, and preliminary results obtained with, a water vapor monior operating at abundance at the level 1 micron precipitable water vapor on a time scale of 1 second and at arbitrary antenna positions are required. This thesis describes the design of, and preliminary results obtained with, a water vapor monitor operating at infrared wavelengths which shows considerable promise for this application. Improvements in, and future plans for, the second generation water vapor monitor currently under development are also discussed.
xiii, 167 leaves : ill. ; 28 cm.

Diffuse reflectance spectroscopy (DRS) is a rapid proximal-sensing method that is being used more and more in laboratory settings to measure soil properties. Diffuse reflectance spectroscopy research that has been completed in laboratories shows promising results, but very little has been reported on how DRS will work in a field setting on soils scanned in situ. Seventy-two soil cores were obtained from six fields in Erath and Comanche County, Texas. Each soil core was scanned with a visible near-infrared (VNIR) spectrometer with a spectral range of 350-2500 nm in four different combinations of moisture content and pre-treatment: field-moist in situ, air-dried in situ, field-moist smeared in situ, and air-dried ground. Water potential was measured for the field-moist in situ scans. The VNIR spectra were used to predict total and fine clay content, water potential, organic C, and inorganic C of the soil using partial least squares (PLS) regression. The PLS model was validated with data 30% of the original soil cores that were randomly selected and not used in the calibration model. The root mean squared deviation (RMSD) of the air-dry ground samples were within the in situ RMSD and comparable to literature values for each soil property. The validation data set had a total clay content root mean squared deviation (RMSD) of 61 g kg-1 and 41 g kg-1 for the field-moist and air-dried in situ cores, respectively. The organic C validation data set had a RMSD of 5.8 g kg-1 and 4.6 g kg-1 for the field-moist and air-dried in situ cores, respectively. The RMSD values for inorganic C were 10.1 g kg-1 and 8.3 g kg-1 for the field moist and air-dried in situ scans, respectively. Smearing the samples increased the uncertainty of the predictions for clay content, organic C, and inorganic C. Water potential did not improve model predictions, nor did it correlate with the VNIR spectra; r2-values were below 0.31. These results show that DRS is an acceptable technique to measure selected soil properties in-situ at varying water contents and from different parent materials.

Experiments were conducted to assess the feasibility of determining the quality attributes of tomato (Lycopersicon esculentum Mill cv 'DRK 453' and 'Trust') based upon visible/near-infrared reflectance (VIS/NIR) spectroscopy. A partial least squares regression (PLS) method was used to build prediction models. Excellent prediction performance was achieved for lycopene content (LC), colour value a*/b* ratio, tomato colour index (TCI), and firmness. Coefficient of determination (R2) for each of the parameters was respectively 0.96, 0.99, 0.99, and 0.97. All these R2 were significant at 1% level. The root mean square errors of prediction (RMSEP) for all the parameters were low indicating the high quality of the fit of the prediction models. The values were 2.15, 0.06, 1.52, and 1.44 for LC, a*/b* ratio, TCI, and firmness, respectively. However, the models for prediction of titratable acidity, soluble solids content (SSC) and acid-Brix ratio showed relatively poor reliability, with R2 value of 0.49, 0.03 and 0.65, and RMSEP of 0.43, 0.15 and 0.08, respectively. Further, a model built by the PLS2 method showed good performance in simultaneously predicting a*/b* ratio, TCI, firmness, and LC of tomato, with R2 values of 0.99, 0.99, 0.97, and 0.92, and RMSEP of 0.06, 1.75, 1.44, and 3.03, respectively. Once again here all the R2 values were significant at 1% level.
Des essais visant à évaluer la faisabilité d'utiliser la spectroscopie de réflectance dans le visible et le proche infrarouge (VIS/PIR) pour déterminer certaines caractéristiques contribuant à la qualité de la tomate (Lycopersicon esculentum Mill. cv. 'DRK 453' et 'Trust') ont été menés. Une analyse de régression partielle par les moindres carrés a servi à bâtir des modèles de prédiction. D'excellentes prédictions ont été obtenues pour la teneur en lycopène (TL), la valeur chromatique a*/b*, l'indice de couleur de la tomate (ICT), et la fermeté. Les coefficients de détermination (R2) pour chacun de ces paramètres ont été de 0.96, 0.99, 0.99 et 0.97. Tous ces R2 ont été significatifs à un niveau de 1%. L'erreur-type de prédiction (ETP) a été petite pour tous ces paramètres, indiquant un très bon degré d'ajustement des modèles. Des valeurs d'ETP de 2.15, 0.06, 1.52 et 1.44 ont respectivement été obtenues pour le TL, le rapport a*/b*, l'ICT, et la fermeté. Cependant, les modèles visant à prédire l'acidité totale, la teneur en solides solubles et le rapport acide-Brix se sont montrés peu fiables avec des valeurs respectives de R2 de 0.49, 0.03 et 0.65 et de ETP de 0.43, 0.15 et 0.08. De plus, un modèle multivariable bâti par une méthode de régression partielle par des moindres carrés (PLS2) s'est montrée très performant pour la prédiction simultanée du rapport a*/b*, de l'ICT, de la fermeté et de la TL avec des valeurs respectives de R2 de 0.99, 0.99, 0.97 et 0.92 et de ETP de 0.06, 1.75, 1.44 et 3.03. Comme auparavant toutes les valeurs de R2 ont été significatives à un niveau de 1%.

Visible and near infrared (NIR) reflectance and transmission spectra (400 - 2500 nm) of various flesh foods in various presentations were examined for qualitative and quantitative analysis. Discriminant functions for muscle types and animal species were included. Lamb muscles (n: 306), chicken breast and thigh muscles (n: 48), bull and steer muscles (n: 103), raw fish (n: 80), fish meal (n: 700) and fish oil (n: 160) samples were examined in the experiments. INTACT and MINCED presentation to the instrument were compared, as well as type of muscle (longissimus dorsi, infra spinatus, supra spinatus, semimembranosus, semitendinosus, rectus femoris), effect of sex and both longitudinal (LS) and transverse section (TS) of the muscle on the optical properties and Partial Least Squares (PLS) calibrations for gross composition. MINCED presentation to the instrument gave the best results for the NIRS calibrations in all the muscle tissues utilized, while, INTACT presentation showed poorer calibrations. Muscle type and sex affect the calibrations. Raw fish and fish by-products, both fish meal and oil had good NIRS calibrations for the twelve parameters analyzed. The results show that NIRS is acceptable as a method for determining gross composition in a wide variety of flesh foods in MINCED presentation. Principal component analyses (PCA) and Soft Independent Modelling of Class Analogy (SIMCA) were used for the authentication and classification between muscles and among animal species. The conclusions of this work are that NIRS can successfully predict chemical composition in different muscles in MINCED rather than INTACT presentation. Classifications using PCA and SIMCA were excellent tools to authenticate flesh foods.

This Dissertation presents the magneto-optical properties of monolayer (ML) transition metal dichalcogenide (TMDC) materials using our several magneto-optical setups that were developed at UB. In this Dissertation, we discuss a magneto-photoluminescence (PL) setup, a broadband magneto-FTIR setup, and a two-color spectroscopy setup in detail. We also discuss the double modulation technique, which we use in two-color spectroscopy.

The primary results of this work include magneto-PL measurements of ML WSe₂ on YIG. We pump these materials with circularly polarized light and analyze with a circular polarizer. We reported a 30% polarization and 10 nm peak shift in a localized state with an applied magnetic field. We see a polarization up to T = 80 K. By changing the magnetic field from –7 Tesla to +7 Tesla, localized impurity-bound exciton states show strong polarization under optical excitation of opposite helicity. Right circularly polarized PL peaks are shifted to lower energies and their PL become stronger than left circularly polarized PL peaks. This is opposite for left circularly polarized peaks. They shift to higher energies (shorter wavelengths) and become weaker than right circularly polarized peaks. We also found that localized states show more polarization than free exciton and trion peaks on YIG substrate.

We also investigated Kerr rotation and Kerr ellipticity properties of ML MoS₂ and ML WSe₂ on YIG with our new broadband magneto—FTIR optical setup. Samples and substrate do not show any Kerr ellipticity features when exposed to a changing magnetic field. All samples show strong magnetic field dependent Kerr rotation signal but we found that ML MoS₂ by itself does not show any magnetic field dependent Kerr rotation signal. We found that there are two broad peaks in the YIG and ML WSe₂ on YIG Kerr rotation spectrum. YIG’s two broad peak centers are located at around 1800 cm^–1 and 2300 cm^–1 and ML WSe₂ on YIG peak centers are located at around 1900 cm ^–1 and 2500 cm^–1. For both samples, these peak intensities are linear with the magnetic field and they are symmetric with respect to B = 0 T. ML WSe₂ on YIG peaks are shifted to higher energies with respect to YIG peak. We also report that the center of the peaks has no shift with a magnetic field.

With our two-color spectroscopy setup, we have tested Imamoglu’s theory that predicts a splitting of dark 2p states at B = 0 Tesla. A circularly polarized laser and a linearly polarized IR laser were used together to excite electrons to dark states. We used red or green laser and CO or CO₂ IR laser together in our experimental setup. Samples are ML MoS₂ on sapphire and ML WS₂ on Si/SiO₂. Within a sensitivity of 10 µrad, we did not see any splitting at B = 0 Tesla on any samples.

Thesis: Ph. D. in Physical Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references.
The primary focus of this thesis is to synthesize biocompatible luminescent nanocrystals for visible and short-wave infrared (1-2 [mu]m, SWIR) imaging applications. Quantum dots (QDs) have been promising fluorescent probes for biomedical imaging due to their high quantum yield (QY), narrow photoluminescence spectra, and excellent photostability. However, challenges remain to be solved to transfer the as-synthesized hydrophobic QD to aqueous solutions while maintaining the high QY and a compact size. This study involves the design and synthesis of a novel ligand that can be introduced to the established QD synthesis, producing norbornene functionalized QDs that can be readily phase transferred into water via norbornene/tetrazine click chemistry, meanwhile allowing flexible functionalization of the QDs by incorporating a functional group on the hydrophilic chain. This ligand system can be applied to a variety of carboxylic-ligand-stabilized QDs, with emission spectra spanning the visible and the SWIR region. The resulting water-soluble QDs exhibit a high QY, a small hydrodynamic diameter (HD), and excellent colloidal stability and pH stability. Further in vitro cell labeling experiments using azido-functionalized QDs demonstrates their potential for cell targeting applications. As in vivo imaging in the SWIR range has further reduced background noise from tissue scattering compared to traditional visible and near infrared (0.7-1 tm, NIR) imaging, images of higher contrast and better resolution can be readily obtained. The next challenge is to develop SWIR emitters that have high quantum efficiency and minimal toxicity, which is of critical importance in order to promote this technology for clinical applications. Our study found that the emission of luminescent gold nanoclusters can be tuned from the visible to the SWIR region by proper selection of ligands and post ligand modifications. The SWIR-emitting gold nanoclusters have a good QY, a HD that is small enough that they exhibit a rapid renal clearance, and images taken in the SWIR region show better resolution of the blood vessels than in the NIR region.
by Yue Chen.
Ph. D. in Physical Chemistry

The eld of plasmonics studies the interaction of light and free electrons in metals, giving rise to excitation of surface waves, on a metallodielectric interface. One branch of plasmonics is the design of metamaterials in visible and infrared spectral range which are articial structures designed to manipulate the propagation of light in a way not possible with conventional materials. This thesis is categorized in 3 main parts. The rst part examines the effects of waveguided modes in Au nanorod metamaterial waveguides. It shows, both theoretically and experimentally, that these materials can be designed to control the sign and magnitude of modal group velocity depending on the geometry and polarization chosen exhibiting high eective refractive indices (up to 10) and have an unusual cut-o from the high-frequency side, providing deep-subwavelength (0/6 { 0/8 waveguide thickness) single-mode guiding. This allows slow light to exist in such waveguides in a controllable environment which is a critical factor for nonlinear and active nanophotonic devices, quantum information processing, buering and optical data storage components. The second part discusses, analytically and numerically, strategies for biosensing and nonlinearity enhancement with hyperbolic nanorod metamaterials. It shows how the sensitivity of unbound, leaky as well as waveguided modes can be enhanced based on geometrical considerations. Additionally, refractive index variation of the host medium produces 2 orders of magni- tude higher sensitivity compared to nanorod or superstrate refractive index changes. In certain congurations, both TE and TM-modes of the metamaterial transducer have comparable sensitivities opening up opportunities for polarization multiplexing in sensing experiments. The gure of merit of the aforementioned structure is one order of magnitude higher than surface plasmon polariton and localized surface plasmon sensors making it ideal for sensitive-dependant applications such as chemo- and biosensors and nonlinear photonic devices. The third part investigates Strontium Ruthenate thin lms as a new material for near-IR plasmonic applications. It is demonstrated that their plasmonic behavior can be optimized by their deposition conditions leading to a selective and tunable plasma frequency in 324 - 392 nm range and epsilon-near-zero wavelength in 1.11 { 1.47 m range. Applications of these lms range from heat-generating nanostructures in the near-IR spectral range, to metamaterial-based ideal absorbers and epsilon-near-zero components, where the interplay between real and imaginary parts of the permittivity in a given spectral range is needed for optimizing the spectral performance.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2020
Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 139-147).
Fluorescence imaging offers high spatio-temporal resolution, low radiation dosage exposure, and low cost among all the available imaging modalities, for example, magnetic resonance imaging, computerized tomography and positron emission tomography. Imaging probes of high emissivity and photostability are the key to achieving fluorescence imaging with high signal-to-background ratio (SBR). One promising approach to developing highly bright and stable imaging probes is through surface plasmon enhanced fluorescence. In the first part of the thesis, we develop a fluorescent probe with high site-specificity and emission efficiency by exploiting the targeting-specificity of M13 virus and co-assembling plasmonic nanoparticles and visible dye molecules on the viral capsid. Practical factors controlling fluorescence enhancement, such as nanoparticle size and dye-to-nanoparticle distance, are studied in this project. Lastly, the highly fluorescent probe is applied for in vitro staining of E.
coli. The methodology in this work is amendable to developing a wide range of affinity-targeted fluorescent probes using biotemplates. Compared to visible and near infrared spectrum, short-wave infrared (SWIR, 900-1700 nm) spectrum promises high spatial resolution and deep tissue penetration for fluorescence imaging of biological system, owning to low tissue autofluorescence and suppressed tissue scattering at progressively longer wavelengths. In the second part of the thesis, a bright SWIR imaging probe consisting of small SWIR dyes and gold nanorods is developed for in vivo imaging. Fluorescence enhancement is optimized by tuning the dye density on the gold nanorod surface. The SWIR imaging probes are applied for in vivo imaging of ovarian cancer. The effect of targeting modality on intratumor distribution of the imaging probes is studied in two different orthotopic ovarian cancer models.
Lastly, we demonstrate that the plasmon enhanced SWIR imaging probe has great potential for fluorescence imaging-guided surgery by showing its capability to detect submillimeter-sized tumors. Apart from enhancing the SWIR down-conversion emission above, surface plasmon enhanced SWIR up-conversion emission is another promising approach to achieving "autofluorescence-free" imaging with minimal tissue scattering. In the third part of the thesis, we use gold nanorods to enhance the up-conversion emission of small SWIR dyes. The mechanism of surface plasmon enhanced up-conversion emission is studied. The up-conversion fluorescence shows much higher SBR than down-conversion fluorescence in non-scatting biological solution and scatting medium. Lastly, we demonstrate in vivo imaging for the first-time using SWIR up-conversion fluorescence with exceptional image contrast.
by Shengnan Huang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering