Entender os processos em superfície/interface de filmes e seus efeitos sobre as propriedades ópticas e elétricas de materiais orgânicos é de grande importância tecnológica. Esta pesquisa descreve a fabricação e caracterização de filmes poliméricos extremamente finos (espessura <10 nm) e homogêneos compostos por camadas de polímero/polieletrólitos e estruturas com modulação de energia ou poços quânticos. O objetivo principal foi o estudo dos processos de transferência de carga e energia em tais estruturas. Os polímeros luminescentes utilizados foram poli(9,9 dioctilfluoreno) (PFO) poli(p-fenileno vinileno (PPV). O PPV foi obtido a partir do precursor poli(cloreto de tetraidrotiofeno de xililideno) (PTHT). A técnica de deposição denominada deposição camada por camada assistida por spin (SA-LbL) foi utilizada para obtenção dos filmes. Medidas de absorbância confirmaram o crescimento linear das camadas para as interfaces polieletrólito/polieletrólito e polímero/polieletrólito. Com o objetivo de entender a transferência do elétron &pi; do polímero conjugado para o polieletrólito, as configurações das estruturas poliméricas foram alteradas através da deposição de diferentes monocamadas de polieletrólito sobre o filme polimérico. Observamos que os elétrons &pi; foram efetivamente transferidos para os polieletrólitos que possuem alta afinidades eletrônica. Este efeito interfere fortemente na absorção bem como nas características de condução do filme polimérico ultrafino. A absorção é restabelecida após a conversão de PTHT em PPV. Medidas de fotoluminescência (PL) em filmes PFO/PPV resultam em curvas de emissão com picos característicos de ambos os polímeros, o que confirma que a técnica SA-LbL permite a deposição de estruturas poliméricas multicamadas. As várias configurações de filmes obtidas elucidaram os processos de transferência que ocorrem em diferentes interfaces, tais como: mudança da sequencia de deposição do polieletrólito, número de camadas duplas PTHT/DBS e a introdução de camadas separadoras. Além disso, um único poço quântico, ou seja, estruturas formadas por uma camada PPV cercada por barreiras de PFO com 10 nm de espessura foram obtidas. Medidas de absorbâcia, PL e excitação mostraram uma eficiente migração estado excitado da barreira de PFO para o PPV (poço). A homogeneidade da imagem confocal, demonstrou um rigoroso controle da camada de cobertura ao nível de um única monocamada e sem contaminação pelos materiais depositados sequencialmente. A microscopia confocal de fluorescência (CFM) e espectroscopia de fluorescência resolvida no tempo (FLIM) foram utilizadas para caracterizar a dinâmica do exciton e o seu confinamento nos poços quânticos. As medidas de CFM demonstraram que excitons que são gerados na barreira de PFO são eficientemente transferidos para o PPV. Além disso, o tempo de decaimento da emissão PFO residual é fortemente reduzido devido a processos de migração concorrentes no poço. O tempo de decaimento de PPV diminui substancialmente para poços com espessuras abaixo de 5 nm como resultado da auto-aniquilação do exciton. Dessa forma, as estruturas de MQW obtidos pela técnica de SA-LbL podem ser usadas para estudar a transferência de energia, efeitos túneis e para a construção de novos dispositivos optoelectrónicos com maior eficiência. / The understanding of surface/interface processes and their effects on optical/electrical properties of organic materials is of strong technological importance. This research describes the fabrication and characterization of extremely thin (thickness <10 nm) and homogeneous multilayered polymeric structures including polymer/poly-electrolyte layers and structures with energy modulation such as quantum well. Our main purpose was the study of charge and energy transfer processes in such energy modulated structures. The luminescent polymers used were Poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) and poly(p-phenylenevinylene) (PPV). PPV has been obtained from the poly(xylyliden tetrahydrothiophenium chloride) (PTHT) precursor. The so-called Spin Self-Assembly Layer-by-Layer deposition method (SA-LbL) was utilized to obtain the films. Absorption measurements confirmed the linear growth of layers using for polyelectrolyte/polyelectrolyte and polymer/polyelectrolyte interfaces. In order to understand the &pi;-electron transfer from the conjugated polymer to charged states of the polyelectrolyte, the configurations of the polymeric structures were modified by depositing different polyelectrolyte monolayer on the polymer film. We observed that &pi;-electrons were effectively transferred to polyelectrolytes that have high electron affinities. This effect strongly affects both absorption and conduction features of such very thin polymeric film. The absorption is restored after the conversion of PTHT in PPV. Photoluminescence measurements on PFO/PPV films result in emission curves with characteristic peaks of both polymers, confirming that SA-LbL technique allows deposition of multilayer polymeric structures. The various film configurations elucidates the transfer processes occurring at different interfaces like: change of polyelectrolyte deposition order, number of PTHT/DBS bilayers and introduction of spacers. In addition, Single Quantum Well (SQW), i.e., structures consisted of PPV layer surrounded of 10 nm thick PFO barriers were obtained. Optical absorption, PL and excitation spectroscopy showed an efficient excited state migration from the PFO barrier to the PPV well. The confocal image homogeneity demonstrated the layer coverage control at a monolayer level and without layer intermixing of the sequentially deposited polymeric materials. High resolution Confocal Fluorescence Microscopy (CFM) and Fluorescence Life spectroscopy and Imaging (FLIM) were used to characterize the exciton dynamics and confinement in quantum well. The CFM measurements demonstrated that excitons generated at the PFO barrier are efficiently transferred to the PPV well. Furthermore, the decay time of the residual PFO emission is strongly reduced due to the competing migration process in the well. The decay time of PPV decreases substantially for well thicknesses below 5 nm as a result of exciton self-annihilation. Thus, the MQW structures obtained by SA-LbL technique can be used to study energy transfer, tunneling effects and to build up new optoelectronic devices with greater efficiency.

This PhD thesis is devoted to study electro-optic properties of Gemanium/Silicon-Germanium (Ge/SiGe) multiple quantum wells (MQWs) for light modulation, detection, and emission on Si platform. It reports the first development of high speed, low energy Ge/SiGe electro-absorption modulator in a waveguide configuration based on the quantum-confined Stark effect (QCSE), demonstrates the first Ge/SiGe photodiode with high speed performance compatible with 40 Gb/s data transmission, and realizes the first Ge/SiGe light emitting diode based on Ge direct gap transition at room temperature. Extensive DC and RF measurements were performed on each tested prototype, which was realized using the same epitaxial growth and fabrication process. Simple theoretical models were employed to describe experimental properties of the Ge/SiGe MQWs. The studies show that Ge/SiGe MQWs could potentially be employed as a new photonics platform for the development of a high speed optical link fully compatible with silicon technology.

Cette thèse est consacrée à l’étude des propriétés optiques et optoélectroniques autour de la bande interdite directe des structures à puits quantiques Ge/SiGe pour la modulation, la photodétection et l’émission de lumière sur la plateforme silicium. Les principaux composants réalisés sont : un modulateur optique en guide d’onde, rapide et à faible puissance électrique, basé sur l’Effet Stark Confiné Quantiquement, les premières photodiodes Ge/SiGe dont le comportement fréquentiel est compatible avec les transmissions de données à 40 Gbit/s, et la première diode à électroluminescence à puits quantiques Ge/SiGe, base sur la transition directe de ces structures et fonctionnant à température ambiante. Les caractérisations statiques et fréquentielles ont été réalisées sur l’ensemble des composants, qui ont tous été fabriqués avec la même structure épitaxiée et les mêmes procédés de fabrication. Des modèles théoriques simples ont ensuite été utilisés pour décrire analyser les comportements observés. Finalement les études menées permettent de conclure que les structures à puits quantiques Ge/SiGe sont un candidat de choix pour la réalisation d’une nouvelle plateforme photonique à haut débit, totalement compatible avec les technologies silicium. / This PhD thesis is devoted to study electro-optic properties of Gemanium/Silicon-Germanium (Ge/SiGe) multiple quantum wells (MQWs) for light modulation, detection, and emission on Si platform. It reports the first development of high speed, low energy Ge/SiGe electro-absorption modulator in a waveguide configuration based on the quantum-confined Stark effect (QCSE), demonstrates the first Ge/SiGe photodiode with high speed performance compatible with 40 Gb/s data transmission, and realizes the first Ge/SiGe light emitting diode based on Ge direct gap transition at room temperature. Extensive DC and RF measurements were performed on each tested prototype, which was realized using the same epitaxial growth and fabrication process. Simple theoretical models were employed to describe experimental properties of the Ge/SiGe MQWs. The studies show that Ge/SiGe MQWs could potentially be employed as a new photonics platform for the development of a high speed optical link fully compatible with silicon technology.

L’amplification optique large bande à base de SOA est devenue indispensable pour la montée en débit des systèmes de transmissions optiques et pour pouvoir exploiter au mieux la bande optique des fibres optiques. Ce travail présente une étude théorique et expérimentale d’un SOA large bande passante développé par Alcatel Thales III-V Lab dans le cadre des projets ANR AROME et UltraWIDE. Dans cette thèse, nous avons d’abord effectué une modélisation semi-phénoménologique du gain matériau et du coefficient de gain d’une structure à base de multi-puits quantiques avec un nombre réduit de paramètres. L’intégration de notre modèle dans un modèle de SOA déjà développé au laboratoire a montré son efficacité pour restituer quantitativement le comportement statiques (gain, facteur de bruit) des nouvelles structures SOA large bande sur une large plage de longueurs d’onde (> 110 nm), de courants d’alimentation et de puissances optiques. A l’aide de ce modèle, nous avons étudié l’influence de la structure du SOA sur la bande passante pour un gain cible en jouant sur la longueur, le nombre d’électrode et le courant d’alimentation du SOA. Nous avons mis en évidence qu’une structure bi-électrodes n’apportait pas d’amélioration de la bande passante optimisée par rapport au cas mono-électrode. En revanche, la structure bi-électrode permet d’optimiser la puissance de saturation et le facteur de bruit du SOA, sans sacrifier ni le gain maximal ni la bande passante optique. Nous avons aussi montré que, pour ce type de composants, une augmentation de la puissance optique injectée pouvait être compensée par une augmentation du courant d’alimentation pour maintenir une large bande passante optique. Nous avons également mis en place deux techniques d’élargissement de la bande passante optique de SOA à large bande. La première technique est fondée sur le filtrage en réflexion spectralement sélectif (ESOA). Le dispositif expérimental a permis d’amplifier simultanément 8 canaux CWDM dans une bande passante (définie à −1 dB) de 140 nm. La deuxième technique, basée sur un amplificateur hybride Raman-SOA, a fourni une bande passante optique (définie à −1 dB) de 89 nm avec un gain de 17 dB. Nous avons ainsi pu réaliser une transmission simultanée de 5 canaux CWDM allant jusqu’à 10 Gb/s sur 100 km. / SOA-based optical amplification became crucial for increasing optical system capacity and to benefit from the broad bandwidth of optical fibers. In this work we present both theoretical and experimental studies for a new broadband SOA developed by Alcatel Thales III-V lab in the framework of AROME and UltraWIDE ANR projects.We developed firstly a semi-phenomenological model for both the material gain and the gain coefficient of a multi-quantum well -based SOA structure with a reduced set of parameters. This material gain model has been integrated in an existing SOA model and proved its performance in reproducing steady state behavior of this new broadband SOA (gain and noise figure) for a wide range of wavelengths, input powers and bias currents. Thanks to this model, we studied the influence of the SOA geometrical structure on the optical bandwidth for a given target gain, by varying length, number of electrodes and bias current. We showed that two-electrode SOA structures do not provide any improvement of the bandwidth compared to the one-electrode case. However, the two-electrode structure allows the optimization of both the SOA saturation power and the noise figure, without sacrificing neither the maximum gain nor the optical bandwidth. We have also shown that for this kind of component, an increase in the injected optical power could be compensated by an increase in the supply current to maintain a wide optical bandwidth.We have also investigated two techniques to widen the optical bandwidth of our broadband SOA. The first one is based on a modification of the SOA structure by introducing a selective reflection filter (ESOA). Its experimental implementation allowed the amplification of an 8-CWDM-channel comb in a bandwidth (defined at -1 dB) of 140 nm. The second one, based on a hybrid Raman-SOA amplifier, provided an optical bandwidth (defined at -1 dB) of 89 nm with a gain of 17 dB. With this last technique, we were able to achieve a 5-CWDM-channel comb transmission up to 10 Gb/s over 100 km.