Quantum Well Infrared Photodetector (QWIP) technology is promising for the development of large format low cost single and dual/multi color infrared sensor arrays. Thanks to the mature III-V semiconductor technology, QWIP focal plane arrays (FPAs) provide high uniformity and excellent noise equivalent temperature difference (NETD) in both long wavelength infrared (LWIR 8-12 &amp / #61549 / m) and mid wavelength infrared (MWIR 3-5 &amp / #61549 / m) bands. This thesis work focuses on the development of large format single and dual color MWIR QWIP FPAs. For single band MWIR detection, we report QWIP FPAs on InP substrate as an alternative to the GaAs based MWIR QWIPs suffering from the degrading effects of lattice mismatched epitaxy. In the course of this work, epitaxial growth conditions of the device structure were optimized and 640&times / 512 AlInAs/InGaAs QWIP FPAs on InP substrate have been fabricated yielding NETD of 22 mK (f/1.5) and background limited performance (BLIP) temperature as high as 115 K In the second part, we report the first voltage tunable 640&times / 512 dual color MWIR QWIP FPA. After optimizing epitaxial growth of AlGaAs/InGaAs material system, we have designed and implemented the device structure to yield voltage tunable spectral response in two different windows in the MWIR band. The FPA provides NETDs of 60 and 30 mK (f/1.5) in colors 1 and 2. The results are very encouraging for the development of low cost dual/multi color FPAs since our approach utilizes one In bump per pixel allowing fabrication of dual color FPAs with the same process steps for single color FPAs.

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Spatial and temporal dynamics of polymer chains play critical roles in their rheological properties, which have a significant influence on polymer processing and fabrication of polymer-based (nano) materials. Many theoretical and experimental studies have aimed at understanding polymer dynamics at the molecular level that give rise to its bulk phase properties. While much progress has been made in the field over the past ~60 years, many aspects of polymers are still not understood, especially in complicated systems such as entangled fluids and polymers of different topologies. In addition, the physical properties of biological macromolecules, i.e. DNA, are expected to affect the spatial organization of chromosome in a cell, which has the potential impact on a broad epigenetics research. Here, we propose new methods for simultaneous visualization of diffusive motion and conformational dynamics of individual polymer chains, two most important factors that characterize polymer dynamics, based on a new single-molecule tracking technique, cumulative-area (CA) tracking method. We demonstrate the applicability of the CA tracking to the quantitative characterization of the motion and relaxation of individual topological polymer molecules under entangled conditions, which is possible only by using the newly-developed CA tracking, using fluorescently-labeled linear and cyclic dsDNA as model systems. We further extend the technique to multi-color CA tracking that allows for the direct visualization and characterization of motion and conformation of interacting molecules. We also develop a new imaging method based on recently developed 3D super-resolution fluorescence microscopy technique, which allows direct visualization of nanoscale motion and conformation of the single molecules that is not possible by any other methods. Using these techniques, we investigate spatial and temporal dynamics of polymers at the single-molecule level, with special emphasis on the effect of topological forms of the molecules and the confined geometry on their spatiotemporal dynamics. Our results demonstrate that the new methods developed in this thesis provide an experimental platform to address key questions in the entangled topological polymer dynamics. The research will provide a platform for developing new polymer-based materials and open the possibility of studying spatial organization of DNA in a confined geometry from physics point of view.

[pt] Dispositivos opto-eletrônicos são elementos semicondutores que convertem radiações eletromagnéticas em corrente elétrica, e vice e versa. Os fotodetectores são dispositivos desse tipo, os quais possuem grande relevância na atualidade, devido a suas diversas aplicações. As pesquisas atuais se concentram no estudo de fotodetectores à base de poços quânticos para operar no infravermelho médio (2-20 m), mais especificamente em super-redes. No presente trabalho foi desenvolvido um fotodetector de duas cores baseado em super-redes assimétricas. O fotodetector construído possui uma rede com duas sessões. A primeira sessão tem cinco poços quânticos e cinco barreiras com 2 nm e 3.5 nm de espessura, respectivamente. A segunda sessão possui cinco poços quânticos e cinco barreiras de 2 nm e 7 nm de espessura, respectivamente. Entre as seções existe um poço quântico de 2.5 nm. O material que forma os poços quânticos é de InGaAs e o material das barreiras é de AlInAs. Esse dispositivo foi capaz de operar como um fotodetector de duas cores operando no modo fotovoltaico detectando radiações de 309 meV e 415 meV. O dispositivo foi capaz de operar em altas temperaturas. A temperatura máxima de operação foi de 245 K. Além disso, ao se aplicar tensões no dispositivo, é possível selecionar a radiação a ser detectada pelo fotodetector. Sendo elas 309 meV ou 415 meV. / [en] Opto-electronic devices are semiconductor elements that convert electromagnetic radiation in electric current. Photodetectors are devices of this type, which are the main relevant ones today due to their diverse applications. Current research focuses on the study of photodetectors based on quantum wells for operation in the medium infrared (2-20 m), more specifically with superlattices. In the present work a photodetector of two cores based on asymmetric superlattice was developed. The built-in photodetector had a superlattice with two sessions The first session had five quantum wells and five barriers with 2 nm and 3.5 nm of thickness, respectively. The second session had five quantum wells and five barriers of 2 nm and 7 nm thick, respectively. Between the sessions there is a 2.5 nm quantum well. The material that formed the quantum wells was InGaAs and the material of the barriers was AlInAs. This device was able to operate as a dual color photodetector operating in the photovoltaic mode detecting radiation of 309 meV and 415 meV. The device was able to operate at high temperatures. The maximum operating temperature was 245 K. In addition, when applying voltages to the device, it is possible to select the detection energy of the photodetector :309 meV or 415 meV.

Le cerveau est un organe complexe composé de neurones et des cellules non-neuronales. La communication entre les neurones a lieu via les synapses, dont le remodelage morphologique est considéré essentiel pour le traitement et le stockage des informations dans le cerveau des mammifères. Récemment, ce point de vue neuro-centré de la fonction synaptique a évolué, en prenant également en compte les processus gliaux à proximité immédiate de la synapse. Cependant, comme leur structure est bien en deçà de la résolution spatiale de la microscopie optique conventionnelle, les progrès dans les enquêtes dans leur environnement physiologique, le cerveau intact, ont été entravés. En effet, on sait peu sur les variations nanométriques de la morphologie des épines dendritiques et l'interaction avec les processus gliaux, et, finalement, comment elles affectent la transmission synaptique in vivo. Dans cette thèse, nous cherchons à visualiser la dynamique de la nano-morphologie des épines dendritiques et les processus gliaux dans le cortex à tonneaux de souris in vivo. Nous avons donc mis en place l’imagerie super-résolution 2P-STED en temps réel, ce qui permet une haute résolution spatiale et la pénétration profonde des tissus, chez la souris anesthésiée in vivo. Nous montrons que la nano-morphologie des épines est diversifiée, variable, mais globalement stable, et que les différences dans la morphologie des épines peut avoir un effet sur leur compartimentation in vivo. En outre, la mise en œuvre de l’imagerie super-résolution en double couleur in vivo et le développement d'une approche de marquage astrocytaire, nous ont permis de fournir la caractérisation à l'échelle nanométrique des interactions neurone-glie. Ces résultats apportent un aperçu sans précédent dans la dynamique de la synapse à l'échelle nanométrique in vivo, et ouvrent la voie à une meilleure compréhension de la façon dont les réarrangements morphologiques des synapses contribuent à la physiologie du cerveau. / The brain is a complex organ consisting of neurons and non-neuronal cells. Communication between neurons takes place via synapses, whose morphological remodeling is thought to be crucial for information processing and storage in the mammalian brain. Recently, this neuro-centric view of synaptic function has evolved, also taking into account the glial processes in close vicinity of the synapse. However, as their structure is well below the spatial resolution of conventional light microscopy, progress in investigating them in a physiological environment, the intact brain, has been impeded. Indeed, little is known on the nanoscale morphological variations of dendritic spines, the interaction with glial processes, and how these affect synaptic transmission in vivo. Here, we aim to visualize the dynamic nano-morphology of dendritic spines in mouse somatosensory cortex in vivo. We implemented super-resolution 2P-STED time-lapse imaging, which allows for high spatial resolution and deep tissue penetration, in anesthetized mice, and show that the nano-morphology of spines is diverse, variable, but on average stable, and that differences in spine morphology can have an effect on spine biochemical compartmentalization in vivo. Moreover, implementation of dual color in vivo super-resolution imaging and a novel astrocytic labeling approach provided the first steps towards nanoscale characterization of neuron-glia interactions in vivo. These findings bring new insights in synapse dynamics at the nanoscale in vivo, and our methodological endeavors help pave the way for a better understanding of how nanoscale aspects of spine morphology and their dynamics might contribute to brain physiology and animal behavior.