[pt] Optomecânica, o estudo de forças induzidas pela luz sobre a matéria, teve grandes avanços nos últimos anos com diversas implicações sobre todas as ciências naturais. Pinças ópticas, por exemplo, são amplamente usadas na física, química e biologia para aprisionar nano e micropartículas com índice de refração maior do que o meio que a cerca usando, em geral, feixes Gaussianos. Generalizando essa técnica, trabalhos recentes começaram a explorar estados de ordem maior dos feixes eletromagnéticos e suas superposições para aprisionamento óptico, criando feixes com fase, modo e amplitude ajustáveis. Esses novos graus de liberdade permitem o uso de potenciais arbitrários e até mesmo forças dependentes do tempo capazes de induzir movimento controlado no objeto aprisionado. Nesse contexto de feixes estruturados, nós podemos explorar não apenas as forças atrativas entre luz e matéria, mas também as forças repulsivas que ocorrem quando o índice de refração da partícula é menor que o do meio circundante. Neste trabalho vamos explorar ambos cenários a partir da criação de feixes holográficos com um Modulador Espacial de Luz (SLM). Mais especificamente, vamos focar na implementação do feixe de foco escuro, ou feixe de garrafa, onde as partículas encontram equilíbrio em uma região sem incidência de luz. Resultados experimentais são apresentados e comparados com simulações numéricas baseadas na teoria de Lorentz-Mie e possíveis aplicações dessas pinças óticas inversas são discutidas em optomecânica e biologia. / [en] Optomechanics, the study of light-induced forces upon matter, has seen tremendous advances in recent years with broad implications to all natural sciences. Optical tweezers, for instance, are now widely used in physics, chemistry and biology to trap nano- and micro-objects with a refractive index greater than of its surrounding medium using typically Gaussian laser beams. Generalizing these techniques, recent works began to explore higher-order states of the electromagnetic field and its superpositions for optical trapping, creating beams with customized phase, mode and amplitude. These new degrees of freedom allows for optical potentials beyond the harmonic approximation, enabling virtually arbitrary potential forms and even time-dependent forces capable of inducing controlled motion on the trapped object. Within this context of structured light beams, we can explore not only the attractive forces between light and matter but the repulsive ones that arise when the particle s refractive index is smaller than that of its medium. In this work we explore both scenarios by creating holographic beams with a Spatial Light Modulator (SLM). Specifically, we focus on the implementation of the dark focus beam, or optical bottle beam, where particles may find equilibrium in a region with no incidence of light. Experimental results are presented and compared to Lorentz-Mie numerical simulations and possible applications of these inverted optical tweezers in optomechanics and biology are discussed.

No description available.

The main objective of this thesis is to present a simple and robust hands-on technology for the fabrication of a microfluidic chip in a laboratory. The purpose of this new technology is to replace the existing PDMS based microfluidic chip used for optical trapping of diverse single nano particles. It also lists the different fabrication methods attempted and the successful integration of this chip to the optical trap system which is used to study binding at the single molecular level. Microfluidics is a quickly growing field which deals with manipulating the fluids in channels whose dimensions are few tens of micrometers. Its potential has a major impact on fields like chemical analysis and synthesis techniques, biological analysis and separation techniques, and optics and information technology. One of the main application of these microfluidic chips is in optofluidics, which is the emerging field of integrated photonics with fluidics. This provides freedom to both fields and permits the realization of optical and fluidic property. It requires small volumes of fluids and connections and eventually performs better than conventional methods of robotic fluid handling. Here, the microfluidic chip is targeted for optical trapping with double nano-hole aperture to trap a single protein. The double nanoholes integrated with this microfluidic chip show that stable trapping can be achieved below flow rates of few μL/min. This has provided many possibilities of co-trapping of proteins and study their interactions. / Graduate

Dans le cadre de l’étude expérimentale des états quantiques intriqués de particules uniques, il est nécessaire de développer des systèmes compacts, robustes et polyvalents. Motivés par la miniaturisation, la stabilité et la flexibilité apportées par les fibres optiques, nous présentons deux expériences où les fibres optiques servent d’interfaces pour piéger des atomes uniques et collecter les photons uniques émis. Dans un premier temps, en combinant une fibre optique monomode avec une lentille asphérique, un faisceau dipolaire permet de piéger un atome de rubidium unique par blocage collisionnel. Le refroidissement et le taux de pertes par collisions assistées par la lumière dans le piège dipolaire sont augmentés via une modulation de l’intensité du faisceau dipolaire dont l’effet sur la durée de vie de l’atome est expliqué. Une source fibrée de photons uniques à la demande est obtenue avec ce dispositif, produisant des photons dans un mode spatial et temporel à priori bien défini. Dans un second temps, nous présentons la conception d’une expérience couplant optimalement une chaîne d’atomes uniques piégés à une cavité Fabry-Pérot fibrée combinée avec une lentille à forte ouverture numérique pour imager et adresser les atomes individuellement. Un dispositif d’ablation laser de précision submicrométrique est alors construit pour réaliser et analyser in situ les formes de miroirs voulues à l’extrémité des fibres optiques. Nous présentons ensuite les cavités fibrées doublement résonantes avec une biréfringence contrôlée réalisées. Nous décrivons également le système expérimental construit pour la production rapide d’un nuage d’atomes froids et leur transport vers la cavité. / The experimental study of entangled quantum states of single particle ensembles requires development of compact, robust and versatile systems. Motivated by miniaturization, stability and flexibility provided by optical fibers as light wave-guides, we present two experiments where optical fibers are used as interfaces for single atoms trapping and single photons collection into their guided modes. The first experiment combines a single mode fiber with an aspherical lens to produce a dipolar beam in which we trap a single rubidium atom by collisional blockade. This fiber-pigtailed optical tweezer is a simple, compact and versatile tool for single cold atom production. Cooling and light-assisted collisional loss rate in the dipole trap are increased by modulating the dipole beam intensity. The modulation and beam polarization effects on atom lifetime are presented and explained. With this setup, we realized a triggered single photon source, whose photons have a priori well defined spatial and spectral mode due to the optical fiber and the atomic transition.In a second part, we present the design of an experiment which optimally couples a trapped single atom register to a fiber Fabry-Pérot cavity and where a high numerical aperture lens allows for individual imaging and addressing. A sub-micron precision laser ablation setup is built to create and to analyze in situ desired mirror shapes on optical fiberend faces. Then, we present the produced double resonant fiber cavities with controlled birefringence. Eventually, we describe the created experimental setup for fast cold atom cloud production and transport towards the cavity.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-09-12T14:28:27Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese _Diógenes Soares Moura_final.pdf: 4560976 bytes, checksum: efbc9854c7666e2a40de8b98b027e62d (MD5) / Made available in DSpace on 2016-09-12T14:28:27Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese _Diógenes Soares Moura_final.pdf: 4560976 bytes, checksum: efbc9854c7666e2a40de8b98b027e62d (MD5) Previous issue date: 2016-02-25 / CAPEs / O presente trabalho explora a utilização de lasers na região do infravermelho do espectro eletromagnético em aplicações biomédicas. O uso dos lasers na indústria, para processamento de materiais e em aplicações médicas, como a realização de cirurgias, têm atraído grande interesse nas últimas décadas. Neste trabalho, laser infravermelho foi explorado no corte de bolsas de sangue e no desenvolvimento de sistema de avaliação de elasticidade de hemácias baseado em técnica de aprisionamento óptico. No corte de bolsas de sangue foram determinados os parâmetros da ablação como tempo de perfuração, taxa de ablação e diâmetro dos furos para diferentes fluências e taxas de repetição do laser. Neste trabalho foram utilizados laser pulsados no regime de femtossegundos, com comprimento de onda de 800 nm, com taxa de repetição de 10 Hz e 1 KHz. Os resultados mostraram uma dependência do processo de ablação com o aumento da fluência e da taxa de repetição do laser. Além disso, foram avaliados os resíduos gasosos emitidos durante o processo de ablação das bolsas. A avaliação dos parâmetros de ablação à laser de bolsas de sangue consiste em um estudo pioneiro e introduz um novo direcionamento no processo de corte das mesmas. No desenvolvimento de um sistema para avaliação automática de elasticidade de hemácias aprisionadas opticamente foram utilizados lasers contínuos nos comprimentos de onda de 785 nm e 1064 nm. O sistema permite obter o valor da elasticidade de uma célula em 20 segundos, o que imprime uma redução significativa do tempo do processo de avaliação (60 ×) comparada ao método convencional. O sistema automático pode ajudar a expandir as aplicações de pinças ópticas em Hematologia e Hemoterapia. Além disto, o sistema construído foi utilizado para avaliar danos em hemácias aprisionadas opticamente. Foi verificada uma dependência da elasticidade das células com o comprimento de onda, potência do laser incidente e com tempo de aprisionamento da hemácia. Observou-se que as hemácias, após 2 minutos de exposição ao laser de 785 nm tornaram-se até ~ 104% menos deformáveis que as hemácias controle. A exposição ao laser de 1064 nm de 2 minutos a 10 mW induziu um aumento de até ~ 20% na rigidez celular. Atribuiu-se a dependência do comprimento de onda dos danos ópticos à absorção do laser pela hemoglobina. As modificações observadas nas propriedades elásticas das células estudadas estabelecem novos limites para aplicações utilizando lasers em hemácias. / This work explores the use of lasers in the infrared region of the electromagnetic spectrum in biomedical applications. The use of lasers in industry for materials processing and in medical applications, such as in surgeries, have attracted great interest in recent decades. In this work, infrared lasers were explored in blood bags cutting and in the development of a red blood cells elasticity evaluation system based on optical trapping technique. For the blood bags cutting process, ablation parameters such as drilling time, ablation rate and ablation diameter for different laser fluence and repetition rates were determined. In this work we used pulsed laser in femtosecond regime, with a wavelength of 800 nm, with repetition rate of 10 Hz and 1 KHz. The results showed a dependence of the ablation process with laser fluence and repetition rate. In addition, the waste gases emitted during the blood bags ablation process were evaluated. The evaluation of the blood bag laser ablation parameters consists of a pioneering study and introduces a new direction in the blood bag cutting process. In the development of a system for automatic evaluation elasticity of optically trapped red blood cells (RBCs), continuous laser at a wavelength of 785 nm and 1064 nm were used. The system allows to obtain the value of cell elasticity in 20 seconds, establishing a significant reduction in the assessment process time (× 60) compared to the conventional method. The automated system can help expand the applications of optical tweezers in Hematology and Hemotherapy. In addition, the constructed system was used to evaluate damage to red blood cells optically trapped. A dependence of the cells elasticity with the wavelength and power laser and with cell time trapping was observed. The results shows that the red blood cells was up to ~104% less deformable after 2 minutes of 785 nm laser exposition. The 2 minutes exposure to 10 mW of 1064 nm laser induced an increase up to ~ 20% on cell rigidity. We ascribed the wavelength dependence of the optical damages to the laser absorption by the hemoglobin. Moreover, the increase of RBCs rigidity could be associated to initial changes optically caused in the hemoglobin after irradiation. The results establish new limits for laser applications in RBCs, by identifying considerable modifications on their elastic properties.

Motivé par leur implication dans le centre réactionnel de l’appareil photosynthétique, puis plus tard, par les défis de la catalyse par transfert multi–électronique, des exemples d'édifices composés de deux porphyrines maintenues face–à–face apparaissent dans les années 70. Les premiers exemples font appel à l’utilisation d’espaceurs rigides qui maintiennent les porphyrines selon une géométrie bien définie permettant d’établir des relations précises entre la structure et les propriétés de ces dérivés. Ce projet de recherche a consisté à synthétiser une « nouvelle génération » de systèmes Pacman, plus flexibles et présentant deux types de conformations : une ouverte et une fermée. En ce sens, ces dérivés peuvent être décrits comme des pinces moléculaires. Le passage d’une conformation à l’autre serait contrôlé par la coordination d’un cation métallique au sein d’un espaceur–ligand. La conformation du système ne dépendrait alors plus de l’espaceur mais serait imposée par la géométrie de coordination du métal. Outre le contrôle conformationnel en fonction de la nature du cation métallique, l’avantage de cette approche est de pouvoir moduler, ou réguler dans le cas d’une coordination réversible, les propriétés physico–chimiques du système par simples interactions de type hôte/invité. Alors que les porphyrines sont supposées se comporter indépendamment dans la forme ouverte, la fermeture de la pince devrait se traduire par un rapprochement des macrocycles selon une disposition cofaciale impliquant des interactions entre les porphyrines. Ainsi, une modification des propriétés physico–chimiques de l’espèce et de son activité est attendue de par la communication électronique et/ou la coopérativité intermétallique établie. Nous nous sommes attachés également à présenter les études physico–chimiques entreprises sur certains systèmes bi– et trimétalliques afin de valider ces différents concepts. / Motivated by their involvement in the reaction center of the photosynthetic apparatus, and later, by the challenges of the multi–electron transfer catalysis, some examples of porphyrin dimer maintained in a face–to–face arrangement, appeared in the seventies. The first examples consisted in rigid spacers, which maintain the porphyrins in a well–defined geometry in order to establish a precise relationship between the structure and the properties of these derivatives. This research project consists in the synthesis of a “new generation” of Pacman systems, more flexible and presenting two types of conformations: one open, the other closed. In this way, these derivatives can be described as molecular tweezers. The way to go from one conformation to the other would be controlled by the coordination of a metal cation within a spacer–ligand. Thus, the conformation of the system will not depend on the spacer (like in the previous Pacman systems) but would be determined by the metal coordination geometry. In addition to the conformational control as a function of the nature of the metal cation, the advantage of this appraoch is to modulate, or regulate in the case of a reversible coordination, the physico–chemical properties of the system by simple host/guest interactions. Although the porphyrins are supposed to act independantly in the open form, the closure of the tweezer would bring the macrocycles closer according to a cofacial arrangement involving interporphyrinic interactions. Thus, a modification of the physico–chemical properties and the activity of the species is expected by the electronic communication between both macrocycles and/or the established bimetallic cooperativity. In order to validate these concepts, physico–chemical studies performed on some bis– and tris–metal systems are described.

With the unique advantage of great isolation from the thermal environment, levitated optomechanics has emerged as a powerful platform for various fields of physics including microscopic thermodynamics, precision measurements, and quantum mechanics. Experiments with optically levitated micro- and nanoparticles have already obtained remarkable feats of zeptonewton force sensing and ground-state cooling. The novel system has also been proposed to assess various theories including the objective collapse models and macroscopic quantum mechanics. <br><div><br></div><div>This thesis reports experimental results on a levitated Cavendish torsion balance, a GHz nanomechanical rotor, and a torque sensor with unprecedented sensitivity realized with optically levitated nanoparticles in a vacuum environment. The system at room temperature achieves a sensitivity of (4.2±1.2)×10−27Nm/ √ Hz surpassing the sensitivity of most advanced nanofabricated torque sensors at cryogenic environments. Calculations suggest potential detection of Casimir torque and vacuum friction under realistic conditions. Moreover, the nanoparticles are driven into ultrafast rotations exceeding 5 GHz, which achieves the fastest humanmade nanomechanical rotor. Such fast rotations allow studies on the ultimate tensile strength of the nanoparticles as well. <br></div><div><br></div><div>Subsequently, the electron spin control of nitrogen vacancies (NV) in optically trapped diamond naoparticles is demonstrated in low vacuum. The configuration is analogous to trapped atoms and ions which serve as a quantum system with internal states. The effect of the air pressure, surrounding gas, and laser power on the electron spin resonance (ESR) are studied, and the temperature of the diamond is also measured with the ESR. The levitated nanodiamonds will provide the means to implement a hybrid spin-optomechanical system.<br></div>

[pt] As pinças ópticas tornaram-se uma ferramenta importante na pesquisa multidisciplinar, permitindo a manipulação e estudo de partículas em micro e nanoescala. Aqui, descrevemos o desenvolvimento de dois experimentos de pinça óptica no cerne da optomecânica levitada: uma pinça óptica a vácuo Gaussiana e uma pinça óptica a vácuo com luz estruturada. No experimento Gaussiano, descrevemos em detalhes sua construção e seu uso para testar características de movimento estocástico sujeito a forças efetivas não-lineares geradas através de feedback elétrico. Em seguida, passamos para a configuração de luz estruturada. Utilizando um Modulador Espacial de Luz, desenvolvemos uma pinça óptica a vácuo com a capacidade de gerar potenciais ópticos arbitrários, incluindo não-linearidades e armadilhas para múltiplas partículas. Os experimentos desenvolvidos neste trabalho abrem caminho para novos métodos de controle de movimento de partículas, forças e interações, expandindo ainda mais a caixa de ferramentas da optomecânica levitada. / [en] Optical tweezers have become an important tool in multidisciplinary research, allowing for the manipulation and study of micro- and nano-scale particles. Here, we describe the development of two optical tweezer experiments at the heart of levitated optomechanics: a Gaussian and a structured light vacuum optical tweezer. In the Gaussian experiment, we describe in detail its construction and its use to test features of stochastic motion subject to nonlinear effective forces generated via electric feedback. Next, we move to the structured light setup. Using a Spatial Light Modulator, we develop a vacuum optical tweezer with the capability of engineering arbitrary optical landscapes, including non-linearities and multi-particle traps. The experiments developed in this work pave the way to novel methods for controlling particle motion, forces and interactions, further extending the levitated optomechanics toolbox.

Depuis les premiers travaux d’Ashkin sur les pinces optiques classiques, beaucoup d’efforts ont été fait pour piéger des nano particules. Néanmoins, elles peuvent difficilement piéger des particules inférieures à 200 nm à cause des limites imposées par la diffraction. Cette limite peut être dépassée grâce aux forces optiques de gradient provenant du champ évanescent généré et amplifié par des nano cavités photoniques. Cependant, cette approche est confrontée à deux verrous importants pour les applications : La surface de piégeage est très faible ce qui rend peu probable la capture d’une nanoparticule animée d’un mouvement brownien et pour les pinces « ultimes » de type nanoantenne où le mode est confiné dans des régions nanométriques, leur excitation en espace libre n’est pas très efficace. L’objectif de ce travail vise à lever ces deux verrous. Pour augmenter la surface de piégeage, nous présenterons d’abord une approche utilisant le mode de Bloch d’une cavité étendue à double période dans un cristal photonique fabriqué sur SOI. Nous montrerons que cette approche permet le piégeage de particules de 200, 100 et 75 nm sur une surface étendue de 5x5 µm² en utilisant un faisceau laser d’excitation en espace libre. Dans un deuxième temps, nous nous intéresserons à l’excitation optique en espace libre de structures nanométriques. Nous présenterons une structure hybride nano antenne – cristal photonique, où le cristal photonique joue le rôle de réservoir à photons pour la nano antenne. Cela permet ainsi un effet « entonnoir à photon» où la lumière issu d’un faisceau large (5µm) est concentrée dans la nanoantenne. Nous démontrerons la pertinence de cette approche par le piégeage particules de 100 nm. / Since the first work on optical tweezers by Ashkin, a lot of efforts have been made to trap nanoparticles. However, optical tweezers are diffraction limited and can hardly trap particles below 200 nm. This limit can be overstepped using the optical gradient forces of an evanescent field generated and amplified by a photonic nano cavity. Nonetheless, this approach faces two major issues for applications: the trapping section is very small, making the capture of a Brownian motion animated particle very unlikely, and for the “ultimate” nano antennas with nanometric optical modes, their excitation from free space is not effective. The goal of this work is to overcome these two difficulties. To increase the trapping surface, we will first present a device using slow Bloch modes within a double period extended cavity designed in a photonic crystal made out of SOI. We will show that this approach allow for the trapping of 200, 100 and 75 nm particles on an extended surface of 5x5 µm² using a free space laser beam excitation. Secondly, we will investigate the free space excitation of nanometric structures. A photonic crystal – nano antenna mixed structure will be presented, where the photonic crystal is used as a photon pool for the nano antenna. This lead to a funnel effect where the light coming from a large free space laser beam (5µm wide) is focused into the nano antenna. The trapping of 100 nm particles will demonstrate the relevance of this approach.

Cette thèse présente la réalisation d’un piège optique dans une configuration originale, le piston optique, où le contrôle sur la phase de l’interférence d’un faisceau incident avec sa réflexion sur un miroir permet de réaliser différents types d’expériences. Nous avons d’abord étudié les propriétés thermodynamiques d’une compression progressive du piston qui fait passer la dynamique de la particule piégée d’une région de stabilité vers une région de bistabilité mécanique. Dans le contexte de la résonance stochastique où une force extérieure périodique est appliquée sur cette dynamique bistable, une approche exploitant le facteur de Mandel ainsi qu’une analyse des délais entre les transitions d’états métastables se révèle efficace pour interpréter nos mesures dans différents régimes de forçage. Nous montrons également comment des nanoparticules métalliques peuvent être piégées aisément dans un tel piston optique et nous exploitons notre configuration pour mesurer de faibles effets de forces optiques. Enfin, nous piégeons des nano-objets chiraux uniques et nous montrons comment la configuration de notre piston permet de réaliser des expériences de reconnaissance chirale par polarimétrie différentielle. / This thesis describes the experimental realization of an original optical trap, the optical piston, where controlling the phase of the interference of an incident beam with its reflection on a mirror allows achieving various experiments. We have first looked into the thermodynamics associated with a progressive compression of the piston leading the dynamics of a trapped particle from a region of stability to a region of mechanical bistability. In the context of stochastic resonance where a periodic external force is applied on this bistable dynamics, an approach exploiting the Mandel factor and a time-delay analysis on the hopping events between metastable states have proven efficient in interpreting the different results acquired in different regimes of drive. We have also shown how metallic nanoparticles can be trapped fairly easily in this kind of optical piston and we exploit our configuration to measure weak optical forces. Finally, we trap unique chiral nano-objects and we show how the configuration of our piston allows the realization of chiral recognition experiments by differential polarimetry.