Les transitions intersousbandes dans les hétérostructures de nitrure d’éléments III ont été intensément étudiées dans le proche infrarouge pour des applications télécoms. L’accordabilité dans le proche infrarouge est rendu possible grâce à la discontinuité de potentiel en bande de conduction qui peut atteindre 1.75 eV pour le système GaN/AlN. Les matériaux nitrures suscitent actuellement un grand intérêt à plus grande longueur d'onde infrarouge. C'est par exemple le développement de détecteurs et d'imageurs rapides à cascade quantique dans la gamme 2-5 µm. C'est aussi l'extension des dispositifs intersousbandes dans le domaine de fréquences THz. Ce travail de thèse porte sur l’étude des transitions intersousbandes dans les puits quantiques GaN/Al(Ga)N épitaxiés par jets moléculaires. Le but est d’accorder ces transitions dans une gamme spectrale très large allant du proche au lointain infrarouge. Je montre que les transitions ISB peuvent être accordées dans la gamme 1-12 µm dans les puits quantiques GaN/AlGaN en phase hexagonale synthétisés selon l'axe polaire c [0001]. Ceci impose l'ingénierie du champ électrique interne, dont la valeur peut atteindre dans le GaN 10 MV/cm. Une solution alternative consiste à utiliser une orientation particulière, dite semipolaire, qui conduit à une réduction du champ électrique interne le long de l'axe de croissance [11-22]. J’ai montré que cette réduction du champ interne permet d’accorder les résonances intersousbandes des puits quantiques GaN/AlN dans le proche infrarouge et j’ai pu estimer le champ en comparant les résultats de spectroscopie et simulations. J’ai d’autre part étudié les propriétés interbandes et intersousbandes des puits quantiques de symétrie cubique, qui par raison de symétrie, ne présentent pas de champ électrique interne. Finalement j’ai mis en évidence les premières transitions intersousbandes aux fréquences THz dans les puits quantiques GaN/AlGaN polaires mais aussi cubiques. / Most of the research on GaN-based intersubband transitions has been focused on near-infrared applications, benefiting from the large conduction band offset between GaN and AlN1.75 eV. Devices such as all-optical switches, electro-optical modulators, quantum cascadedetectors, or light emitters have been demonstrated at short infrared wavelengths. Nitridematerials are currently attracting a great interest at longer infrared wavelengths, for example, forthe development of high-speed quantum cascade detectors and imagers in the range 2-5 µm. Inaddition, there is a great interest to extend the operation of nitride intersubband devices to theTHz frequency range especially for the development of quantum cascade lasers operating at non-cryogenic temperature.This work is focused on the study of intersubband transitions in GaN/Al(Ga)N quantumwells grown by molecular beam epitaxy. The goal is to tune these transitions in a broad spectralrange, from near to far infrared. I show that intersubband transitions may be tuned withinthe range 1-12 µm in the polar GaN/AlGaN quantum wells. This requires the engineering of theinternal electric fields, which can be as high as 10 MV/cm in GaN/AlN quantum wells. Analternative approach is to use a particular orientation, known as semipolar, which leads toa reduction of the internal electric field along the growth axis [11-22]. I show that this reductionof the internal field induces a redshift of the intersubband energy allowing to reach the mid-infrared domain. I was able to estimate the electric field in semi-polar structures by comparingthe results of spectroscopy and simulations. I also investigate interband andintersubband optical properties of cubic GaN/AlN quantum wells, for which the internal field isabsent due to the high symmetry of the cubic crystal. Finally, I report the first observation of theintersubband absorption at terahertz frequencies in polar GaN/AlGaN step quantum wells andin cubic quantum wells.

Le tellurure de mercure et de cadmium (HgCdTe ou MCT) est un matériau reconnu pour la physique de la matière condensée, dont l'histoire, datant aujourd'hui de plus de cinquante ans, constitue un excellent exemple des progrès remarquables réalisés dans la recherche sur les semi-conducteurs et les semi-métaux. Notre travail est principalement motivé par l’intérêt fondamental que suscitent ces systèmes, mais notre recherche peut également avoir un impact pratique (indirect) sur la médecine, la surveillance ou la détection de l’environnement ainsi que sur les systèmes de sécurité. Cela peut aider à améliorer les performances des photodétecteurs dans la limite des grandes longueurs d'onde ou à faciliter la fabrication de dispositifs émettant de la lumière.La présente thèse de doctorat vise principalement à combler certaines des lacunes de notre compréhension de la structure de bande électronique des hétérostructures 2D et quasi-2D basées sur les matériaux HgTe/HgCdTe et InAs/InSb, qui peuvent être transformés en phase topologiquement isolante à l'aide des paramètres de croissance. Pour explorer leurs propriétés, la technique expérimentale de base, la magnéto-spectroscopie infrarouge et THz fonctionnant dans un large éventail de champs magnétiques, est combinée à des mesures complémentaires de magnéto-transport. Cette combinaison de méthodes expérimentales nous permet d’obtenir de précieuses informations sur les états électroniques non seulement à l’énergie de Fermi, mais également dans son voisinage relativement large. Diverses hétérostructures ont été étudiées avec des caractéristiques globales et/ou spécifiques déterminées principalement par les paramètres de croissance.La réponse magnéto-optique observée, due aux excitations intra-bande (résonance cyclotron) et interbandes (entre les niveaux de Landau) peut être interprétée dans le contexte d'études antérieures sur des échantillons 3D, des puits quantiques et des super-réseaux, mais également en rapport aux attentes théoriques. Ici, nous visons à obtenir une explication quantitative des données expérimentales recueillies, mais également à développer un modèle théorique fiable. Ce dernier comprend le réglage précis des paramètres de structure de bande présents dans le modèle établi de Kane, mais surtout, l'identification de termes supplémentaires pertinents (d'ordre élevé) nécessaires pour parvenir à un accord quantitatif avec nos expériences. On peut s’attendre à ce que les corrections dues à ces termes supplémentaires affectent davantage les sous-bandes de valence, généralement caractérisées par des masses effectives relativement importantes et, par conséquent, par une grande densité d’états ou, lorsque le champ magnétique est appliqué, par un espacement assez étroit (et mélange important) des niveaux de Landau. / Mercury cadmium telluride (HgCdTe or MCT) is a time-honored material for condensed matter physics, whose history  nowadays more than fifty years long  may serve as an excellent example of remarkable progress made in research on semiconductors and semimetals. The ternary compound HgCdTe implies two important aspects, which largely contributed to its undoubted success in solid-states physics.The present PhD thesis primarily aims at filling some of existing gaps in our understanding of the electronic band structure in 2D and quasi-2D heterostructures based on HgTe/HgCdTe and InAs/InSb materials, which both may be tuned into topologically insulating phase using particular structural parameter. To explore their properties, the primal experimental technique, infrared and THz magneto-spectroscopy operating in a broad of magnetic fields, is combined with complementary magneto-transport measurements. This combination of experimental methods allows us to get valuable insights into electronic states not only at the Fermi energy, but also in relatively broad vicinity.The observed magneto-optical response - due to intraband (cyclotron resonance) and interband inter-Landau level excitations - may be interpreted in the context of previous studies performed on bulk samples , quantum wells and superlattices, but also compared with theoretical expectations. Here we aim at achieving the quantitative explanation of the collected experimental data, but also further developing a reliable theoretical model. The latter includes the fine-tuning of the band structure parameters present in the established Kane model, but even more importantly, identifying additional relevant (high-order) terms and finding their particular strengths, needed to achieve quantitative agreement with our experiments. One may expect that corrections due to these additional terms will more affect the valence subbands, which are in general characterized by relatively large effective masses. Consequently, valence subbands have larger density of states compared to conduction band or, when the magnetic field is applied, rather narrow spacing (and possibly large mixing) of Landau levels.

Cette thèse présente l'étude théorique et expérimentale de la génération et de la mise en forme d'impulsions térahertz (THz). Dans un premier temps, nous avons étudié la génération d'impulsions THz par redressement optique d'impulsions laser femtosecondes intenses dans des cristaux semiconducteurs de ZnTe. Nous avons mis en évidence une forte dépendance de l'efficacité de ce processus de génération avec l'intensité de l'impulsion laser génératrice. Ceci se traduit en particulier par un décalage progressif du spectre vers les basses fréquences et par une évolution anormale de l'énergie THz avec l'intensité laser. Ces comportements résultent d'une combinaison de trois phénomènes : la déplétion de l'impulsion laser au cours de sa propagation dans le cristal, l'absorption de l'onde THz par les porteurs libres créés par absorption à deux photons et une modification de la condition d'accord de phase induite par les porteurs chauds. Dans un deuxième temps, nous avons développé une approche analytique permettant de générer des impulsions THz de formes particulièrement intéressantes pour les expériences de spectroscopie cohérente ou de contrôle cohérent. Nous avons notamment généré des paires d'impulsions verrouillées en phase, des trains d'impulsions, ainsi que des impulsions THz accordables de grande finesse spectrale. Cette technique repose sur le redressement optique d'impulsions laser femtosecondes mises en forme à l'aide d'un masque à cristaux liquides placé dans le plan de Fourier d'une ligne à dispersion nulle. Afin de démontrer la validité de notre approche, nous avons également développé un programme de simulation qui donne des résultats en très bon accord avec l'expérience.

Until recently, there had been a gap between the output frequencies of electronic and optical sources, which included waves of frequencies around 300 GHz to 3 THz and was known as the Terahertz gap. After the development of sources and detectors that operated at these frequencies, Terahertz radiation began to find its way through a variety of applications such as surveillance, spectroscopy and medical imaging. Terahertz radiation has been used in medical imaging experiments on different in-vitro and some in-vivo biological tissues and has shown promising results in differentiating certain features in those tissues. Moreover, it has demonstrated well in detecting certain polar molecules due to these molecules’ fingerprint in Terahertz range of frequencies. Considering these facts, Terahertz has been proved to have the potential for being a perspective medical imaging method, which can be used as a complement to other imaging techniques such as MRI or X-ray or even as a separate method. Due to the capacity of Terahertz radiation, much research is being done on using Terahertz generation-detection set-ups for medical imaging and improving the imaging parameters of these set-ups to capture more precise and meaningful images. In this thesis, the imaging parameters of two different THz imaging set-ups have been studied and compared. One of these imaging set-ups is a THz pulse set-up with photoconductive dipole antennas as source and detector and the other one is a continuous-wave set-up with a backward wave oscillator as the source and a Golay cell as the detector. To the best of our knowledge, a comparative analysis of the imaging parameters of these two types of THz imaging set-ups has not been performed previously. In this thesis, parameters such as modulation transfer function (MTF), resolution and beam profile have been measured through the experiments, for both the THz pulse and THz CW imaging set-ups. These results are compared to the results obtained by theoretical formulas and the reason for any differences occurred between these two results has been explained. Moreover, the imaging parameters found from the experiments for the two set-ups have been compared together and similarities and differences have been discussed. In this thesis, a set of experiments has also been done to verify the capability of the two imaging set-ups for in-vitro tooth imaging, towards developing THz imaging systems suitable for clinical imaging application. These experiments have been performed on a tooth crown sample with the pulse set-up and on a tooth cross-section sample with the continuous-wave set-up. The capability of our THz pulse imaging system to distinguish thickness variations in a tooth crown sample by time-of-flight imaging has been shown and discussed.

Until recently, there had been a gap between the output frequencies of electronic and optical sources, which included waves of frequencies around 300 GHz to 3 THz and was known as the Terahertz gap. After the development of sources and detectors that operated at these frequencies, Terahertz radiation began to find its way through a variety of applications such as surveillance, spectroscopy and medical imaging. Terahertz radiation has been used in medical imaging experiments on different in-vitro and some in-vivo biological tissues and has shown promising results in differentiating certain features in those tissues. Moreover, it has demonstrated well in detecting certain polar molecules due to these molecules’ fingerprint in Terahertz range of frequencies. Considering these facts, Terahertz has been proved to have the potential for being a perspective medical imaging method, which can be used as a complement to other imaging techniques such as MRI or X-ray or even as a separate method. Due to the capacity of Terahertz radiation, much research is being done on using Terahertz generation-detection set-ups for medical imaging and improving the imaging parameters of these set-ups to capture more precise and meaningful images. In this thesis, the imaging parameters of two different THz imaging set-ups have been studied and compared. One of these imaging set-ups is a THz pulse set-up with photoconductive dipole antennas as source and detector and the other one is a continuous-wave set-up with a backward wave oscillator as the source and a Golay cell as the detector. To the best of our knowledge, a comparative analysis of the imaging parameters of these two types of THz imaging set-ups has not been performed previously. In this thesis, parameters such as modulation transfer function (MTF), resolution and beam profile have been measured through the experiments, for both the THz pulse and THz CW imaging set-ups. These results are compared to the results obtained by theoretical formulas and the reason for any differences occurred between these two results has been explained. Moreover, the imaging parameters found from the experiments for the two set-ups have been compared together and similarities and differences have been discussed. In this thesis, a set of experiments has also been done to verify the capability of the two imaging set-ups for in-vitro tooth imaging, towards developing THz imaging systems suitable for clinical imaging application. These experiments have been performed on a tooth crown sample with the pulse set-up and on a tooth cross-section sample with the continuous-wave set-up. The capability of our THz pulse imaging system to distinguish thickness variations in a tooth crown sample by time-of-flight imaging has been shown and discussed.

The photoconductive method is one of the oldest methods for the generation of THz room temperature operated THz electromagnetic waves. The THz photoconductive source has operated at a lower power level in the order of hundreds of nW. In addition, the energy conversion of optical to THz efficiency has remained extremely low. One of the most efficient THz photoconductive sources is a trap-enhanced field (TEF) effect source. The field is measured to contain more than 90% of the total DC bias within the first 5 µm of an 80 µm gap between the electrodes reaching kV/cm with only a modest bias. The overall THz power, however, has remained low, due to its rapid saturation. To date, there has been a limited understanding of the TEF effect. In this thesis, a more detailed experimental investigation of TEF effect current transport and field distribution based on annealing is presented to explain some of the underlining physics of TEF effect. A spatially extended line excitation is introduced to effectively reduce the screening effect while still exploiting the TEF region to maintain high efficiency and reach the µW regime. The record efficiency reached by this method is demonstrated. An experimental demonstration with a numerical analysis of the line excitation is presented. The spectral analysis of both a point and a line excitation demonstrate that the line excitation spectrum is not only comparable to that of the point excitation, but also extends the range of useful lower frequency content. To further improve the THz efficiency, the line excitation THz array is investigated.

Les protéines qui ne possèdent pas de structure unique dans leur forme fonctionnelle constituent la classe des protéines intrinsèquement dépliées (IDPs). Ces dernières sont ubiquitaires dans une cellule et sont connues pour former des agrégats impliqués dans une large variété de maladies. Malgré leurs conformations étendues qui résultent en une large interface avec l'eau environnante, très peu d'informations sont connues sur l'interaction des IDPs avec l'eau. L'eau est parfois appelée la matrice de la vie car elle est indispensable à la plupart des processus biologiques, tels que le repliement, la stabilité ou l'activité des protéines. La protéine tau est une IDP qui régule la dynamique de croissance des microtubules dans les neurones, et dont la fibrillation en fibres de type amyloïde est l'une des marques caractéristiques de la maladie d'Alzheimer. Ce projet de thèse se propose d'explorer l'importance biologique de la dynamique de l'eau autour des IDPs. Nous combinons des méthodes expérimentales et computationnelles, incluant la diffusion incohérente de neutrons, la spectroscopie terahertz, la diffusion de rayons X aux petits angles, et les simulations de dynamique moléculaire, dans le but d'étudier la dynamique de l'eau d'hydratation de la protéine tau, dans ses formes native et fibrillaire. Pour les IDPs comme pour les protéines globulaires, il est montré que la diffusion translationnelle de l'eau d'hydratation permet l'existence des mouvements de larges amplitudes de la protéine, indispensables à la fonction biologique de cette dernière. En comparant avec la forme native, nous mettons aussi en évidence une augmentation de la mobilité de l'eau d'hydratation de la forme fibrillaire de tau. Nous proposons que cette augmentation joue un rôle dans la formation des fibres. De plus, l'étude de la dynamique collective de l'eau d'hydratation montre que la protéine tau influence un volume d'eau deux fois moindre qu'une protéine globulaire équivalente, ce qui pourrait être impliqué dans son mécanisme de liaison avec un partenaire. En conclusion, en étudiant les propriétés dynamiques de l'eau autour des IDPs, ces travaux de thèse suggèrent que la dynamique de l'eau d'hydratation pourrait jouer un rôle fondamental dans les mécanismes de liaison et de fibrillation des IDPs. / Proteins that do not have a well-defined structure in their functional state are referred to as intrinsically disordered proteins (IDPs). IDPs are ubiquitous in biological cells and their aggregation is involved in many diseases. The extended conformations of IDPs result in a large water interface, yet, interactions between IDPs and water are only scarcely documented. Water has been termed the matrix of life because it is essential for a variety of molecular processes, including protein folding, stability, and activity. The IDP tau regulates microtubule activity in neurons and is known to form amyloid fibers that are one of the hallmarks of Alzheimer disease. In this PhD thesis, the biological relevance of water dynamics around IDPs is addressed. We combine computational and experimental approaches, including all-atom MD simulations, incoherent neutron scattering, terahertz spectroscopy and small angle X-ray scattering, to study the hydration water dynamics of the tau protein in its native and fibrillated states. Firstly, a translational diffusion of hydration water molecules is found to be essential for biologically relevant dynamics of both IDPs and globular proteins. Secondly, compared to monomers, we find an enhancement of hydration water mobility around tau amyloid fibers that is suggested to play a role in fiber formation. Finally, the investigation of collective water dynamics reveals that the tau protein influences about two times less water molecules than a globular protein, which might be involved in tau's binding mechanisms. In conclusion, this piece of work investigated the dynamical properties of water around IDPs and suggests that the hydration water dynamics might play fundamental roles in binding and aggregation of IDPs.

Submitted by Marta Toyoda (1144061@mackenzie.br) on 2018-02-26T20:41:23Z No. of bitstreams: 2 Luís Olavo de Toledo Fernandes.pdf: 15592142 bytes, checksum: 23803d88659c9d0dbb0c2713d9228601 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Paola Damato (repositorio@mackenzie.br) on 2018-03-08T11:22:45Z (GMT) No. of bitstreams: 2 Luís Olavo de Toledo Fernandes.pdf: 15592142 bytes, checksum: 23803d88659c9d0dbb0c2713d9228601 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-03-08T11:22:45Z (GMT). No. of bitstreams: 2 Luís Olavo de Toledo Fernandes.pdf: 15592142 bytes, checksum: 23803d88659c9d0dbb0c2713d9228601 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-06-22 / Fundação de Amparo a Pesquisa do Estado de São Paulo / Fundo Mackenzie de Pesquisa / Previous sub-THz studies were derived from single event observations. Spectral trends for a larger collection of sub-THz bursts have been analyzed for the first time. It consists of a set of 16 moderate to small impulsive solar radio bursts observed at 0.2 and 0.4 THz by the Solar Submillimeter-wave Telescope (SST) between 2012 and 2014 at El Leoncito, in the Argentinean Andes.The peak burst spectra included data from new solar patrol radio telescopes (45 and 90 GHz),and were complemented with microwave data obtained by the RSTN, when available. We evaluate critically errors and uncertainties in sub- THz flux estimates caused by calibration techniques and the corrections for atmospheric transmission, and introduce a new method to obtain uniform flux scale criterion for all 16 events. The sub-THz bursts were searched during reported GOES soft x-ray events of class C or larger, during periods of the SST observations. Seven out of 16 events exhibit spectral maxima in the range 5-40 GHz with fluxes decaying at sub-THz frequencies (3 of them associated to GOES class X, and 4 to class M). Nine out of 16 events exhibited the sub-THz spectral component. From these, 5 events exhibited the sub-THz emission fluxes increasing with frequency separated from the microwave spectral component (2 classified as X and 3 as M) and 4 events have been detected at sub-THz frequencies only (3 classified as M and 1 as C). The results suggest that the THz component might be always present, with the minimum turn-over frequency increasing as a function of the energy of the emitting electrons. In view of the peculiar nature of many sub-THz bursts events, their better understanding requires further investigations of bursts examined on the standpoint of SST observations alone. / Estudos prévios de explosões solares na faixa sub-THz foram derivados de observações de eventos isolados. Tendências espectrais para uma coleção de eventos sub-THz foram analisadas pela primeira vez. O trabalho consiste no estudo e comparação de um conjunto de 16 explosões solares impulsivas muito bem detectadas, classificadas como fracas ou moderadas, observadas em 0,2 e 0,4 THz pelo Telescópio Solar para Ondas Submilimétricas (SST – 𝑆𝑜𝑙𝑎𝑟 𝑆𝑢𝑏𝑚𝑖𝑙𝑙𝑖𝑚𝑒𝑡𝑒𝑟−𝑤𝑎𝑣𝑒 𝑇𝑒𝑙𝑒𝑠𝑐𝑜𝑝𝑒) entre os anos de 2012 e 2014, no parque de 𝐸𝑙 𝐿𝑒𝑜𝑛𝑐𝑖𝑡𝑜, nos Andes Argentinos. Os espectros destas explosões são complementados com dados dos rádio polarímetros (POEMAS - 𝑃𝑂𝑙𝑎𝑟𝑖𝑧𝑎𝑡𝑖𝑜𝑛 𝐸𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑜𝑓 𝑀𝑖𝑙𝑙𝑖𝑚𝑒𝑡𝑒𝑟 𝐴𝑐𝑡𝑖𝑣𝑖𝑡𝑦 𝑎𝑡 𝑡ℎ𝑒 𝑆𝑢𝑛) em 45 e 90 GHz, e também com dados em microondas, obtidos pela Rede de Telescópios Solar em Rádio (RSTN – 𝑅𝑎𝑑𝑖𝑜 𝑆𝑜𝑙𝑎𝑟 𝑇𝑒𝑙𝑒𝑠𝑐𝑜𝑝𝑒 𝑁𝑒𝑡𝑤𝑜𝑟𝑘), quando disponíveis. Foram avaliados criticamente os erros e incertezas na estimativa de fluxos na faixa sub-THz, causados pelas técnicas de calibração e correções para transmissão atmosférica, e, assim, introduzido um novo método para obtenção de uma escala de fluxo uniforme, com o mesmo critério para todos os 16 eventos. Os eventos detectados na faixa sub-THz foram analisados e comparados com eventos observados em raios X pelo satélite GOES - 𝐺𝑒𝑜𝑒𝑠𝑡𝑎𝑡𝑖𝑜𝑛𝑎𝑟𝑦 𝑂𝑝𝑒𝑟𝑎𝑡𝑖𝑜𝑛𝑎𝑙 𝐸𝑛𝑣𝑖𝑟𝑜𝑛𝑚𝑒𝑛𝑡𝑎𝑙 𝑆𝑎𝑡𝑒𝑙𝑙𝑖𝑡𝑒, classificados como C, M, ou X, para o mesmo período de operação do SST. A análise estatística é referente a este conjunto de explosões solares muito bem detectadas, onde 7 dos 16 eventos exibiram valores de fluxo máximos na faixa entre 5-40 GHz, com fluxos decaindo nas frequências sub-THz (sendo 3 associados à classe X, e 4 à classe M). Nove dos 16 eventos exibiram a componente espectral sub-THz. Destes, 5 eventos apresentaram emissões na faixa sub- THz com fluxos crescentes com a frequência, separadamente da componente espectral em microondas (2 classificados como X e 3 como M) e 4 eventos foram detectados apenas nas frequências sub-THz (3 com classificação M e 1 com C). Os resultados sugerem que a componente THz pode estar sempre presente, com uma frequência mínima de inversão espectral crescente em função da energia dos elétrons de emissão.

In this work, different optical techniques have been explored to study and characterize crude oil and its asphaltene. Crude oil is extremely complex fluid used to produce fuel for a wide range of applications. The characterization of this fluid is key for optimum operations in the oil and gas industry. First, we demonstrate the application of gold nanorods in characterizing a different set of crude oils. We utilize the high sensitivity of the Localized Surface Plasmon Resonance (LSPR) of the nanorods to the surrounding environment to measure the crude oil refractive index. We immobilized the nanorods on a glass substrate and took the measurement in a reflection configuration. The setup and the nanorods were calibrated using different fluids with known refractive index, and a sensitivity of 247 nm/RIU and a resolution of 0.013 RIU have been achieved. In addition to the simplicity of this approach, it has eliminated the absorption issue and made it possible to measure high optical density crude oils with typical Visible-NIR wavelengths. Surface-Enhanced Raman Spectra (SERS) can also be measured. SERS can provide additional useful information, especially to some applications such as downhole fluid analysis, where confirmation of the hydrocarbons presence is necessary. In the second part of this work, we used Terahertz Time-Domain Spectroscopy (THz-TDS) to study the asphaltene in three different crude oils. THz-TDS has a feature of measuring the amplitude and time delay and consequently the refractive index and absorption coefficient spectra simultaneously. Our approach is based on measuring the THz signal from neat crude oil samples and comparing it with the THz signal after removing the asphaltene from the samples (maltene). The results show that the difference in the time delay and the peak amplitude between the neat oil and the maltene have a linear relation with the asphaltene content. The refractive index spectra of different asphaltenes show variation in the low THz frequencies and comparable spectra in the higher frequencies. The absorption of asphaltene was mild and no distinctive absorption feature was observed except for some narrow absorption peaks that we attributed to water molecules adsorbed on the asphaltene. / Graduate

Le contrôle des ondes électromagnétiques joue un rôle fondamental dans les technologies photoniques actuelles. De nos jours, on assiste à une demande croissante de composants agiles capable d'absorber efficacement les ondes électromagnétiques dans divers gamme de fréquences. Habituellement, ces absorbeurs s'appuient sur les résonances plasmoniques qui apparaissent dans les métaux nobles dans la gamme visible. Cependant, l'extension des propriétés plasmoniques aux spectres infrarouge et THz nécessite des matériaux adéquats ayant un comportement métallique à ces fréquences. Dans ce travail, nous étudions numériquement et expérimentalement les structures métal-isolant-métal (MIM) réalisées à partir de semi-conducteur hautement dopé Si: InAsSb qui a un comportement métallique dans la gamme infrarouge. Dans la deuxième partie, nous avons amélioré l'efficacité des résonateurs MIM en utilisant des métamatériaux hyperboliques qui miniaturisent les résonateurs. Dans la dernière partie, nous proposons un design universel ultra-mince qui permet de dépasser les contraintes associées au choix des matériaux et permettant la réalisation d'un absorbeur fonctionnant sur une gamme spectrale allant de l'infrarouge aux micro-onde. / The control of light absorbance plays a fundamental role in today's photonic technologies. And the urge to design and develop flexible structures that can absorb electromagnetic waves is very growing these days. Usually, these absorbers relies on plasmonic resonances that arise in noble metals in the visible range. However, the extension of the plasmonic properties to the infrared and THz spectra requires adequate materials that have a metallic behavior at these frequencies. In this work, we study numerically and experimentally the metal-insulator-metal (MIM) structures realized from highly doped semiconductor Si:InAsSb that has a metallic behavior in the infrared range. In the second, part we improved the efficiency of the MIM resonators by using hyperbolic metamaterials that also miniaturize the resonators. In the last part, we propose an ultra-thin universal design that overcomes the material barrier so that the total absorption can be achieved for different spectral ranges without changing the material.