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In this study, we fabricated an electrically wavelength-tunable resonant-cavity light emitting diode (RCLED). It was achieved by the combination of an AlGaInAs quantum well structure with an intra-cavity liquid crystal material. In the phase modulator layer, we used nematic liquid crystal (NLC) and cholesteric liquid crystal (CLC), respectively, comparing their difference in the infrared-spectrum. When inserting NLC, the anisotropic properties of liquid crystal enable continuous tuning of mode emission along the extraordinary direction and provide a 58 nm tuning range. The optical characteristics of this device are polarization dependent. On the contrary, the CLC-based device is polarization independent because any polarization of incident light experiences the same averaged refractive index. However, the phase difference of CLC is less than NLC, only a 41 nm tuning range of this sample. We also simulated and discussed experimental results of NLC-based RCLED. The optical pumping of the active region is realized by a CW laser at 1064 nm wavelength and observed at room temperature.

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Techniques for adapting metamaterials for the improvement of RF energy harvesting and infrared photodetection are demonstrated using experimental and computer simulation methods. Two methods for RF energy harvesting are experimentally demonstrated and supported by computer simulation. In the first method, a metamaterial perfect absorber (MPA) is made into a rectenna capable of harvesting RF energy and delivering power to a load by soldering Schottky diodes onto connected split ring resonator (SRR) structures composing the planar metasurface of the perfect absorber. The metamaterial rectenna is accompanied by a ground plane placed parallel to it, which forms a Fabry-Perot cavity between the metasurface and the ground plane. The Fabry-Perot cavity stores energy in the form of standing waves which is transferred to the SRR structures of the metasurface as AC currents that are rectified by the diodes to create DC power. This type of design enables highly efficient energy harvesting for low input power, creates a large antenna capture area, and uses elements with small electrical size, such that 100 uW of power (enough to operate simple devices) can be captured at ambient intensities ~ 1 - 2 uW/cm2. Two designs using this method are presented, one that operates for linear polarizations at 0.9 GHz and a smaller polarization-independent design that operates around 1.5 GHz. In the second method, the energy stored in the standing waves of an MPA Fabry-Perot cavity is instead harvested by placing a separate energy harvesting antenna within the cavity. The cavity shapes and enhances the incident electric field, and then the separate energy harvesting antenna is designed to be inserted into the cavity so that its shape and/or radiation pattern matches the electric field lines within the cavity and maximally extracts the stored energy. This method allows for great customization of antenna design parameters, such as operating frequency, polarization dependence, and directionality, by swapping out different metasurface and antenna designs. Using this method, the amount of power harvested by a simple dipole rectenna placed within a cavity is improved by a factor of 18 as compared to what it would harvest by itself at an ambient intensity of 35 nW/cm2. Lastly, the addition of plasmonic structures to DWELL (quantum dot-in-a-well) infrared photodetectors is investigated by computer simulation. DWELL photodetectors have the potential to one day replace standard mercury cadmium telluride detectors by being cheaper alternatives with a higher operating temperature. The inclusion of gold plasmonic structure arrays into DWELL detectors enables excitation of surface plasmon polariton modes that increase the responsivity of the detector to incident infrared radiation. The peak responsivity of a DWELL detector is demonstrated to improve by a factor of 8 for a 1 um thick layer of plasmonic structures and by a factor of 15 for a 2 um thick layer. These works are steps forward in making RF energy harvesting practically useful and for improving infrared photodetector performance.

In this thesis, we report the development of two types of optical sensors, one for high temperature pressure measurements and the other for real-time particle detection. With a high melting temperature (over 2000°C), low optical loss, and excellent corrosion resistance, sapphire (α-Al₂O₃) is ideal for high temperature sensing applications. Fabry-Perot (FP) cavity with optical interrogation of pressure response. The prototype is based on an extrinsic FP interferometer design and is constructed by combining reactive ion etching (RIE) with direct wafer bonding. Long-term testing proves that the adhesive-free wafer bond is sufficient to create a sealed Fabry-Perot cavity as a pressure transducer. Pressure measurement over a range of 6 to 200 psi has been demonstrated at room temperature using white-light interferometry. For the other sensor, the goal is to detect the presence of micro- and nanoparticles in real time. The sensor is based on a silica fiber taper, and we aim to detect particle presence by measuring optical scattering and absorption induced by particles attached to the taper surface. To establish the relationship between particle density and optical transmission loss, we first consider a model where Au nanospheres are self-assembled on taper surface through electrostatic interaction. An analytical model is established to describe the adsorption of gold nanospheres onto cylindrical and spherical silica surfaces from quiescent aqueous particle suspensions. The curved surfaces of the fiber taper and microspheres are coated with nm-thick layer of a polycation, enabling irreversible adsorption of the negatively charged spheres. Our results fit well with theory, which predicts that the rates of particle adsorption will depend strongly on the surface geometry. In particular, adsorption is significantly faster on curved than on planar surfaces at times long enough that the particle diffusion length is large compared to the surface curvature. This is of particular importance for plasmonic sensors and other devices where particles are deposited from a suspension onto surfaces which may have non-trivial geometries. We have established a theoretical model that can describe optical loss generated by particles on taper surface. This theory is validated by measuring, in real time, optical loss during the self-assembly of gold nanoparticles. We find that the measured optical loss can be quantitatively explained by the presence of multiple guided modes within the fiber taper region. Based on this work, we incorporate a fiber taper into a cascade impactor and show that welding aerosols attached to the fiber taper surface can induce measurable transmission loss during the welding process. / Ph. D.

Ce travail de recherche a été mené afin d'introduire une nouvelle classe de résonateurs Fabry-Pérot (FP) : les cavités FP incurvées basées sur des miroirs de Bragg sans revêtement, de forme cylindrique sont obtenues par micro-usinage du silicium. Une autre spécificité est la longueur de la cavité relativement grande (L> 200 µm) combinée à un haut facteur de qualité Q (jusqu'à 10^4 ), pour répondre aux applications de type spectroscopie d'absorption améliorée par résonance optique, dans lesquelles le produit Q.L est une figure de mérite. Dans ce contexte, l'architecture de base a été modélisée analytiquement pour déterminer les modes transverses d'ordre élevé supportés par de telles cavités. Par conséquent, les conditions expérimentales qui conduisent à une excitation préférentielle (ou rejet) de ces modes ont été testées menant à la validation de notre modèle théorique et à une meilleure compréhension du comportement de la cavité. Une seconde architecture,basée sur la cavité FP incurvée avec une lentille cylindrique a été développée dans le but de fournir une architecture plus stable. Cette dernière a été également modélisée, fabriquée et caractérisée, menant à l'amélioration attendue en termes de performances. D'un autre côté, un point surlignant l'une des applications potentielles que nous avons identifiées pour les cavités incurvées est présentée en insérant la cavité dans un système électromécanique. Ceci consiste à exciter et mesurer les vibrations d'amplitude nanométrique par couplage opto-mécanique dans un résonateur mécanique MEMS intégrant une cavité optique FP. Enfin, comme complément à notre étude sur les résonateurs, nous avons commencé à explorer les applications des interféromètres optiques à base de miroirs de Bragg en silicium. À cette fin, un microsystème de mesure optique a été conçu, fabriqué et caractérisé, il consiste en une sonde optique pour la profilométrie de surface dans des milieux confinés, basé sur un interféromètre de Michelson monolithique en silicium / This research work has been conducted to introduce a novel class of Fabry-Perot (FP) resonators : curved FP cavity based on coating-free Bragg mirrors of cylindrical shape, obtained by silicon micromachining. Another specificity is the rather large cavity lengths (L>200 µm) combined with high quality factor Q (up to 104), for the purpose of applications requiring cavity enhanced absorption spectroscopy, in which the product Q.L is a figure of merit. In this contest, the basic architecture has been modeled analytically to know the high order transverse modes supported by such cavities. Hence, the experimental conditions which lead to preferential excitation (or rejection) of these modes have been tested experimentally leading to the validation of our theoretical model and to a better understanding of the cavity behaviour. A second architecture, based on the curved FP together with a fiber rod lens has been developed for the purpose of providing stable designs. It was also modeled, fabricated and characterized leading to the expected performance improvements. On another side, a highlight on one of the potential applications that we identified for the curved cavities is presented by inserting the cavity into an electro-mechanical system. It consists of exciting and measuring tiny vibration through opto-mechanical coupling in a MEMS mechanical resonator embedding an FP cavity.Finally, as a complement to our study on resonators, we started exploring applications of optical interferometers based on similar micromachined silicon Bragg mirrors. For this purpose, an optical measurement microsystem was designed, fabricated and characterized ; it consists of an optical probe for surface profilometry in confined environments, based on an all-silicon Michelson interferometer

This research work has been conducted to introduce a novel class of Fabry-Perot (FP) resonators : curved FP cavity based on coating-free Bragg mirrors of cylindrical shape, obtained by silicon micromachining. Another specificity is the rather large cavity lengths (L>200 µm) combined with high quality factor Q (up to 104), for the purpose of applications requiring cavity enhanced absorption spectroscopy, in which the product Q.L is a figure of merit. In this contest, the basic architecture has been modeled analytically to know the high order transverse modes supported by such cavities. Hence, the experimental conditions which lead to preferential excitation (or rejection) of these modes have been tested experimentally leading to the validation of our theoretical model and to a better understanding of the cavity behaviour. A second architecture, based on the curved FP together with a fiber rod lens has been developed for the purpose of providing stable designs. It was also modeled, fabricated and characterized leading to the expected performance improvements. On another side, a highlight on one of the potential applications that we identified for the curved cavities is presented by inserting the cavity into an electro-mechanical system. It consists of exciting and measuring tiny vibration through opto-mechanical coupling in a MEMS mechanical resonator embedding an FP cavity.Finally, as a complement to our study on resonators, we started exploring applications of optical interferometers based on similar micromachined silicon Bragg mirrors. For this purpose, an optical measurement microsystem was designed, fabricated and characterized ; it consists of an optical probe for surface profilometry in confined environments, based on an all-silicon Michelson interferometer

Gravitational waves have been predicted by Einstein in his General Relativity theory. Theyare perturbation of the space-time metric and we try to reveal them by laser interferometry. More precisely,gravitational wave detectors are km long Michelson interferometers combined with Fabry-Perot cavities.The network of first generation detectors (Virgo, LIGO, GEO) did not permit a direct detection afterseveral observational runs in coincidence at the nominal sensitivity. A second generation of detectors is inpreparation with in particular the European project Advanced Virgo. This detector should have a sensitivityincreased by an order of magnitude compared to Virgo. The interferometer mirrors play a crucial role inthe Advanced Virgo sensitivity as it is limited by the mirror thermal noise in the mid-frequency regionand by the amount of photons collected in the interferometer cavities at high frequencies. The high powercirculating in the Fabry-Perot cavities induces important thermal lensing effect. This thesis is interestedfirst in the thermal lensing effect in the interferometer for different optical configurations. Then we areinterested in the mirrors composing the Fabry-Perot arm cavity from the calculation of the requirements interms of flatness to the realization of the mirrors flatness and its measurement. The mirror flatness shouldbe sub-nanometric in order to limit the optical losses in the Fabry-Perot cavities to reduce the effect of theshot noise and of the diffused light. We will see the correction of the substrates flatness by the so-calledcorrective coating technique. Finally, we study the uniformity of the dielectric multilayer coating depositionnecessary to obtained high-reflective mirrors. We study in particular the planetary motion of the substratesin the coating machine.

Les ondes gravitationnelles ont été prédites par Einstein dans sa théorie de laRelativité Générale. Elles sont des perturbations de l’espace-temps que lon essaie de mettre en évidence parinterférométrie laser. Plus précisément les détecteurs sont des interféromètres de Michelson de plusieurs kmde long combinés avec des cavités Fabry-Perot afin d'augmenter la sensibilité de linstrument. La premièregénération de détecteurs (Virgo, LIGO, GEO) n’a pas permis d’obtenir une détection directe malgré plusieursphases d’observations en coïncidence à la sensibilité prévue. Une seconde g´enération de détecteurs estactuellement en préparation avec notamment le projet européen Advanced Virgo. Ce détecteur devraitavoir une sensibilité améliorée d’un ordre de grandeur par rapport à linterféromètre Virgo. Les miroirs del’interféromètre jouent un rôle primordial dans la sensibilité d’Advanced Virgo puisque celle-ci est limitéeà dans les fréquences médianes par le bruit thermique des miroirs et aux hautes fréquences par la quantitéde photons que lon arrive à collecter dans les cavités de linterféromètre. La haute puissance contenue dansles cavités Fabry-Perot induit des effets de lentille thermique importants. Cette thèse s’intéresse dans unpremier temps aux effets de lentille thermique dans linterféromètre pour différentes configurations optiques.Par la suite, nous nous intéresserons aux miroirs qui composent les cavités Fabry-Perot depuis la définitiondes besoins en termes de planéité à la réalisation de cette planéité et à sa mesure. La planéité de ces miroirsdoit être sub-nanométrique de faon à limiter les pertes optiques dans les cavités Fabry-Perot et ainsi r´eduireles effets du bruit de photons et de la lumière diffusée. Nous verrons la réalisation de la correction de laplanéité des substrats par la technique dite du traitement correctif. Nous étudierons aussi l’uniformité dudépôt des couches minces diélectriques nécessaires à l’obtention de surface hautement réfléchissante avec enparticulier l’étude du mouvement planétaire des substrats dans la machine de dépôts. / Gravitational waves have been predicted by Einstein in his General Relativity theory. Theyare perturbation of the space-time metric and we try to reveal them by laser interferometry. More precisely,gravitational wave detectors are km long Michelson interferometers combined with Fabry-Perot cavities.The network of first generation detectors (Virgo, LIGO, GEO) did not permit a direct detection afterseveral observational runs in coincidence at the nominal sensitivity. A second generation of detectors is inpreparation with in particular the European project Advanced Virgo. This detector should have a sensitivityincreased by an order of magnitude compared to Virgo. The interferometer mirrors play a crucial role inthe Advanced Virgo sensitivity as it is limited by the mirror thermal noise in the mid-frequency regionand by the amount of photons collected in the interferometer cavities at high frequencies. The high powercirculating in the Fabry-Perot cavities induces important thermal lensing effect. This thesis is interestedfirst in the thermal lensing effect in the interferometer for different optical configurations. Then we areinterested in the mirrors composing the Fabry-Perot arm cavity from the calculation of the requirements interms of flatness to the realization of the mirrors flatness and its measurement. The mirror flatness shouldbe sub-nanometric in order to limit the optical losses in the Fabry-Perot cavities to reduce the effect of theshot noise and of the diffused light. We will see the correction of the substrates flatness by the so-calledcorrective coating technique. Finally, we study the uniformity of the dielectric multilayer coating depositionnecessary to obtained high-reflective mirrors. We study in particular the planetary motion of the substratesin the coating machine.

La technologie RFID (Radio Frequency Identification) prend une place de plus en plus importante dans la société d'aujourd'hui notamment dans des domaines aussi variés que la santé, la sécurité, la logistique... Le développement de cette technologie met en évidence de nouvelles contraintes comme la réduction des zones de lecture et la géo-localisation pour le stockage et le suivi de marchandises. Dans ce contexte, la thèse s'est focalisée sur le développement d'antennes pour lecteur RFID dans le cadre du projet SPINNAKER piloté par TAGSYS RFID et soutenu par OSEO. L'objectif de cette étude est de concevoir des antennes compactes et directives à polarisation circulaire en bande UHF et SHF. L'antenne hélice présente toutes ces caractéristiques à l'exception de la hauteur, très importante dès que l'on souhaite obtenir des performances élevées surtout en gain. Dans ce manuscrit, trois solutions sont proposées pour réduire la hauteur de l'antenne hélice tout en répondant aux cahiers des charges. La première solution consiste à utiliser un réflecteur de forme cylindrique ou conique qui permet de réduire la hauteur d'une antenne hélice classique d'un facteur quatre pour atteindre 0,9λ. La réduction de la hauteur se traduit par une augmentation de la surface autour de l'antenne avec une dimension latérale de 2,3λ. La seconde solution consiste à utiliser l'antenne hélice avec une cavité Fabry-pérot. La hauteur du système antennaire obtenue est de 0,5λ avec un diamètre de 2λ. La dernière solution développée dans la thèse introduit une surface CMA à la solution précédente qui permet de réduire la hauteur à 0,25λ. Toutes les solutions proposées ont été validées expérimentalement. / Over the past 20 years, the RFID (Radio Frequency Identification) technology is having a huge expansion. Nowadays, it is frequently used in different areas as the health, the security and the logistic. A lot of researches are ongoing on this topic, especially in order to reduce the reading zone of the readers and to locate the tags. This thesis focuses on the development of new antennas for Readers RFID devices and is part of the SPINNAKER project supported by OSEO. The antennas requirements are circular polarization, high directivity and gain with low profile. The helix antennas meet all these requirements except the axial length. In this manuscript, we propose three solutions to reduce the helix antenna axial length. The first one uses a cylindrical or conical optimal reflector to reduce the length by four. This reduction affects directly the surface witch increases up to 2.3λ. The second solution uses the helix antenna as a circular polarization feed for a Fabry-Perot (FP) cavity. The final antenna presents a cavity height of 0.5λ and a 2λ diameter. The last solution conserves the FP cavity in which we include an Artificial Magnetic Conductor (AMC) to reduce the cavity height to 0.25λ. All these solutions are validated by measurements.