Les nonlinéarités dans les systèmes nanomécaniques peuvent provenir d’effets dispersif ou dissipatif et ce dans divers systèmes (résistifs, inductifs et capacitifs). Au-delà de l’intérêt fondamental pour tester la réponse dynamique d’un système non-linéaire à plusieurs dégrées de libertés, les nonlinéarités de tels systèmes ouvre la voie vers des capteurs nanomécanique et le traitement du signal. Le résonateur nanomécanique dont la réponse nonlinéaire est étudié, est une membrane suspendue à cristal photonique bidimensionnel utilisée comme miroir déformable. Sa faible masse et sa haute réflectivité en font un candidat idéal pour l’électro-opto-mécanique. L’actuation d’une telle membrane dans le domaine fréquentiel du MHz est rendu possible par des électrodes inter-digitées en dessous de la membrane assurant ainsi l’uniformité de la force d’actuation sur cette dernière. La fabrication de telles structures est basée sur l’intégration hétérogène 3D.La force électrostatique qui s’applique sur la membrane induit des non-linéarités mécaniques avec notamment un effet bistable, des résonances superharmoniques et des résonances stochastiques.La membrane est mise en mouvement par un potentiel électrique V(t) = Vdc + Vac cos(w.t), où Vdc est l’amplitude du courant continu, Vac l’amplitude du courant alternatif à la fréquence d’excitation w;. Le système se comporte alors comme une capacité de sorte que la force qui s’applique sur la membrane varie de manière quadratique avec la tension appliquée. Selon la tension DC ou AC, le comportement de la structure est différent. L’augmentation de la tension DC induit une augmentation de la tension de polarisation sur le matériau qui par conséquent modifie la fréquence propre de la membrane. Tandis que l’augmentation de la tension AC cause l’augmentation de l’amplitude des oscillations de la membrane pouvant aller jusqu’à atteindre le régime non-linéaire.Dans une première série de mesure, la membrane est excitée à la résonance avec une fréquence w; égale à la fréquence du mode mécanique fondamental wm. A partir de la réponse fréquentielle du système, il est possible d’identifier différents modes mécaniques de la membrane sondé optiquement. Pour une excitation plus importante, il est possible d’observer des effets de bistabilité mécanique. Ces non-linéarités sont dues à l’élongation au niveau des points d’ancrage de la membrane.La méthode la plus commune pour agir sur la membrane est l’excitation proche de la résonance fondamentale. Cependant la technique de la résonance superharmonique peut également être utilisée. Cela consiste à appliquer la fréquence d’excitation w; à une fréquence égale à wm/n où n est un entier. La possibilité d’utiliser cette technique est fortement dépendante des nonlinéarités présentes dans le système. Ainsi, l’existence d’une résonance super harmonique à wm/n résulte de la présence d’une nonlinéarité d’ordre n. Dans une seconde série de mesure, un balayage des résonances superharmoniques en fonction de la fréquence et de la puissance a été réalisé en modulant la tension à la fréquence wm/n et en enregistrant la réponse de la membrane autour de wm. Il a été ainsi possible d’observer des résonances superharmoniques allant de n=2 jusqu’à 8. Il a également été possible d’obtenir l’évolution de la phase le long des résonances et ce pour toutes celles observées.Dans une dernière série de mesure, nous utilisons la nonlinéarité présente pour observer des effets de résonance stochastique. L’idée est d’amplifier un signal de faible amplitude (basse fréquence) en injectant du bruit (haute fréquence) dans le système nonlinéaire. Dans le cas de notre système, nous avons été capables d’observer des résonances stochastiques à la fois en amplitude et en phase. Une étude comparative de ces deux régimes est détaillée. Le fait de pouvoir observer la résonance stochastique en phase peut permettre d’envisager la réalisation de communications codées en phase. / Nonlinearities in nanomechanical systems can arise from various sources such as spring and damping mechanisms and resistive, inductive, and capacitive circuit elements. Beyond fundamental interests for testing the dynamical response of discrete nonlinear systems with many degrees of freedom, non-linearities in nanomechanical devices, open new routes for nanomechanical sensing, and signal processing.The nonlinear response of a nanomechanical resonator consisting in a suspended photonic crystal membrane acting as a deformable mirror has been investigated. The low-mass and high reflectivity of suspended membranes pierced by a two-dimensional photonic crystal, makes them good candidates as electro-optomechanical resonator. Actuation of the membrane motion in the MHz frequency range is achieved via interdigitated electrodes placed underneath the membrane. The choice of these electrodes is due to the fact they are able to uniformly actuate these membranes. The processing of such platforms relies on 3D-heterogenous integration process.The applied electrostatic force induces mechanical non-linearities, in particular bistability, superharmonic resonances and stochastic resonance.The membrane is actuated by an electric load V(t) = Vdc + Vac cos(w.t), where Vdc is the DC polarization voltage, Vac the amplitude of the applied AC voltage, and w; the excitation frequency. The system acts as a capacitive system and thus the force applied on the membrane varies as a quadratic function of the applied voltage. Application of either DC or AC voltages can have different implications. Increasing the DC voltage increases the polarizing voltage on the material which in turn causes modulation of the eigenfrequency of the membranes. While an increase in the periodic AC voltage causes the membrane to oscillate more, pushing the system towards non-linear regime.In a first series of experiments, the membrane is actuated resonantly, with an excitation frequency w; equal to the fundamental mechanical modes frequency wm. From the frequency response spectra of the system it was possible to identify different mechanical modes of these membranes via optical measurements. For increased actuation voltages, bistability effects are observed with two different behaviors (spring hardening or softening). The mechanical nonlinearities due to stretching at the clamping point dominate the resonator dynamics.The most commonly used method to act upon the membrane is the primary-resonance excitation, in which the frequency of the excitation is tuned closed to the fundamental natural frequency of the nanostructure. Superharmonic resonance can also be implemented. It consists in applying an excitation frequency w; equal to wm/n, with n being integer. Existence of these superharmonic resonances is highly dependent on the non-linearity of the system. For example existence of n-th order non-linearity results in presence wm/n superharmonic resonance. In a second series of experiments, frequency-power sweep for superharmonic resonance has been performed, by modulating the electric load at a frequency wm/n and recording the response of the membrane at the fundamental frequency wm. High-order superharmonic resonances are observed with n=2 up to 8. Under superharmonic excitation, the control of the phase across the resonance has been shown for every observed resonance.In the next set of experiments, we used the nonlinearity existing in the system to perform stochastic resonance. The idea of stochastic resonance is amplification of a weak signal (with low frequency) by means of noise injected (higher frequency) in a nonlinear system. For our system we were able to achieve stochastic resonance with both amplitude and phase noise. A comparative study between these two schemes was also done in details. The idea of observing stochastic resonance in phase is very interesting as it opens doors to realize phase encoded communications.

[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.

The focus of this dissertation is the study of measuring light not by energy transfer as is done with a standard photodetector such as a photographic film or charged coupled device, but rather by the forces which the light exerts on matter. In this manner we are able to replace or complement standard photodetector-based light detection techniques. One key attribute of force detection is that it permits the measurement of light over a very large range of frequencies including those which are difficult to access with standard photodetectors, such as the far IR and THz. The dissertation addresses the specific phenomena associated with optically induced force (OIF) detection in the near-field where light can be detected with high spatial resolution close to material interfaces. This is accomplished using a scanning probe microscope (SPM), which has the advantage of already having a sensitive force detector integrated into the system. The two microscopies we focus on here are atomic force microscopy (AFM) and nearfield scanning optical microscopy (NSOM). By detecting surface-induced forces or force gradients applied to a very small size probe (~ 20 nm diameter), AFM measures the force acting on the probe as a function of the tip-sample separation or extracts topography information. Typical NSOM utilizes either a small aperture (~ 50 150  nm diameter) to collect and/or radiate light in a small volume or a small scatterer (~ 20 nm diameter) in order to scatter light in a very small volume. This light is then measured with an avalanche photodiode or a photomultiplier tube. These two modalities may be combined in order to simultaneously map the local intensity distribution and topography of a sample of interest. A critical assumption made when performing iv such a measurement is that the distance regulation, which is based on surface induced forces, and the intensity distribution are independent. In other words, it is assumed that the presence of optical fields does not influence the AFM operation. However, it is well known that light exerts forces on the matter with which it interacts. This light-induced force may affect the atomic force microscope tip-sample distance regulation mechanism or, by modifying the tip, it may also indirectly influence the distance between the probe and the surface. This dissertation will present evidence that the effect of optically induced forces is strong enough to be observed when performing typical NSOM measurements. This effect is first studied on common experimental situations to show where and how these forces manifest themselves. Afterward, several new measurement approaches are demonstrated, which take advantage of this additional information to either complement or replace standard NSOM detection. For example, the force acting on the probe can be detected while simultaneously extracting the tip-sample separation, a measurement characteristic which is typically difficult to obtain. Moreover, the standard field collection with an aperture NSOM and the measurement of optically induced forces can be operated simultaneously. Thus, complementary information about the field intensity and its gradient can be, for the first time, collected with a single probe. Finally, a new scanning probe modality, multi-frequency NSOM (MF-NSOM), will be demonstrated. In this approach, the tuning fork is driven electrically at one frequency to perform a standard tip-sample distance regulation to follow the sample topography and optically driven at another frequency to measure the optically induced force. This novel technique provides a viable alternative to standard NSOM scanning and should be of particular interest in the long wavelength regime, e.g. far IR and THz.

No description available.

<p dir="ltr">As the design of computer chips heavily relies on computer simulations, it is envisioned that numerical modeling will play an increasingly important role in the development of unconventional computing technologies. This thesis studies the computational frameworks related to the development of unconventional computing, including probabilistic computing and quantum computing. The capability of probabilistic computing in solving NP-complete number theory problems is demonstrated. Generalized Helmholtz decomposition is shown as a theoretical basis for quantization of electromagnetic fields via numerical mode decomposition. A 2D demonstration of numerical quantization with finite difference method is presented. A computational framework amenable to integral equation solver is proposed to investigate the scattering effect on momentum-entangled photons from spontaneous parametric downconversion. A generic model to investigate field-matter interaction with nonlinearity is presented.</p>

<p>One of the fundamental predictions of quantum mechanics is the occurrence of random fluctuations which can induce a measurable force between neutral objects, known as the Casimir effect. Casimir effect has attracted a lot of interest in both theoretical and practical work since the first prediction in 1948 because it is the most accessible evidence of quantum electromagnetic fluctuations in vacuum. Besides, it has prospective applications for nanotechnology and for studying fundamental physical theories beyond the standard model. In this dissertation, we report the experimental and theoretical progress towards realizing Casimir-based devices and long sought-after vacuum friction. </p> <p><br></p> <p>First, we propose and experimentally realize the first Casimir diode system that can regulate energy transfer along one direction through quantum vacuum fluctuations. This is the first experimental demonstration of non-reciprocal energy transfer by Casimir effects. We develop a dual-cantilever vacuum system which can be used to measure the Casimir force at separations from 50 nm to 1000 nm.  Parametric coupling scheme is applied to the system to couple two cantilevers with different resonant frequencies by Casimir interaction. By controlling the system near the exceptional point, we are able to break the time reversal symmetry and observe the non-reciprocal energy transfer. </p> <p><br></p> <p>The description of the Casimir diode system is followed by an experimental demonstration of the Casimir transistor system where we achieve the first measurement of Casimir interaction between three macroscopic objects. Three cantilevers can be coupled through quantum vacuum fluctuations by the parametric coupling scheme. Moreover, we have realized the first three-terminal Casimir transistor system that can switch and amplify quantum vacuum mediated energy transfer. These two Casimir-based devices will have potential applications in sensing and information processing.  </p> <p><br></p> <p>Subsequently, the first observation of Casimir mediated non-contact friction is demonstrated experimentally. When two parallel surfaces are moving with a relative velocity, they will experience quantum vacuum friction force which tries to slow down the relative motion because of quantum vacuum fluctuations. The quantum vacuum friction comes from the exchange of virtual photons between two moving bodies.  We have designed a novel method to detect the Casimir force mediated non-contact friction force between two harmonic oscillators. The non-contact friction comes from the interaction of virtual photons and phonons. We have experimentally detected the effect of non-contact friction and successfully measured the friction force at different velocities. </p> <p><br></p> <p>In the latter part of this thesis, two theoretical proposals about detecting the Casimir torque and rotational quantum vacuum friction torque by a levitated optomechanical system are discussed. The optically levitated nanoparticle system is a good candidate for precision measurements because it can achieve an ultrahigh mechanical quality factor due to the well isolation from the thermal environment. The calculation of the Casimir torque on a levitated nanorod near a birefringent plate is demonstrated. The calculation of the rotational quantum vacuum friction torque on a rotating nanosphere near a plate is also presented. By comparing these small torques to the sensitivity of our levitation system, we show that it is feasible to detect the Casimir torque and the rotational quantum vacuum friction torque under realistic conditions in the near future. </p> <p><br></p>

The Giant Magellan Telescope (GMT) will be featured with two Gregorian secondary mirrors, an adaptive secondary mirror (ASM) and a fast-steering secondary mirror (FSM). The FSM has an effective diameter of 3.2 m and built as seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope subapertures and fast guiding to attenuate telescope wind shake and mount control jitter. This tip-tilt capability thus enhances performance of the telescope in the seeing limited observation mode. As the first stage of the FSM development, Phase 0 study was conducted to develop a program plan detailing the design and manufacturing process for the seven FSM segments. The FSM development plan has been matured through an internal review by the GMTO-KASI team in May 2016 and fully assessed by an external review in June 2016. In this paper, we present the technical aspects of the FSM development plan.

<div>Aperiodic structures offer new functionalities for control, manipulation, and sensing that can benefit applications in all frequency ranges. We present a study of the influence of the degrees of freedom from a binary aperiodic nanostructure in free space, where each pixel is either the scatterer or the background, that uses a multivariate statistical analysis to examine the covariance matrix of the output field distributions. The total variance of the output fields and the rank can be evaluated to provide quantitative measurements of control. In addition, the field statistics provide an improved understanding of the scattering properties of aperiodic structures.</div><div><br></div><div><br></div><div><div>It has been proposed that structuring a metal surface can substantially increase the optical pressure over that possible with a planar interface. Based upon the forces on the mirrors of a one-dimensional asymmetric Fabry-Perot cavity, we show that the sum of the pressures on both mirrors increases through asymmetry and with quality factor. Using cavity quality factor as a measure, we present the physical basis of the enhanced pressure on a nanostructured metallic surface as being due to an array of asymmetric resonant cavities.</div></div><div><br></div><div><div>With use of optimized, aperiodic structures, more control and higher pressure should be possible. We present a design method by which the electromagnetic pressure on a nanostructured binary material can be controlled in terms of both the enhancement and the direction. This analysis offers new avenues for optomechanics.</div></div>

Part I of this thesis is concerned with cavity optomechanical systems subject to periodic driving. We develop a Floquet approach to solve time-periodic quantum Langevin equations in the steady state, show that two-time correlation functions of system operators can be expanded in a Fourier series, and derive a generalized Wiener-Khinchin theorem that relates the Fourier transform of the autocorrelator to the noise spectrum. Weapply our framework to optomechanical systems driven with two tones. In a setting used to prepare mechanical resonators in quantum squeezed states, we nd and study the general solution in the rotating-wave approximation. In the following chapter, we show that our technique reveals an exact analytical solution of the explicitly time-periodic quantum Langevin equation describing the dual-tone backaction-evading measurement of a single mechanical oscillator quadrature due to Braginsky, Vorontsov, and Thorne [Science 209, 547 (1980)] beyond the commonly used rotating-wave approximation and show that our solution can be generalized to a wide class of systems, including to dissipatively or parametrically squeezed oscillators, as well as recent two-mode backaction-evading measurements. In Part II, we study nonreciprocal optomechanical systems with several optical and mechanical modes. We show that an optomechanical plaquette with two cavity modes coupled to two mechanical modes is a versatile system in which isolators, quantum-limited phase-preserving, and phase-sensitive directional ampliers for microwave signals can be realized. We discuss the noise added by such devices, and derive isolation bandwidth, gain bandwidth, and gain-bandwidth product, paving the way toward exible, integrated nonreciprocal microwave ampliers. Finally, we show that similar techniques can be exploited for current rectication in double quantum dots, thereby introducing fermionic reservoir engineering. We verify our prediction with a weak-coupling quantum master equation and the exact solution. Directionality is attained through the interference of coherent and dissipative coupling. The relative phase is tuned with an external magnetic eld, such that directionality can be reversed, as well as turned on and off dynamically.

This thesis contains several theoretical studies on optomechanical systems, i.e. physical devices where mechanical degrees of freedom are coupled with optical cavity modes. This optomechanical interaction, mediated by radiation pressure, can be exploited for cooling and controlling mechanical resonators in a quantum regime. The goal of this thesis is to propose several new ideas for preparing meso- scopic mechanical systems (of the order of 10^15 atoms) into highly non-classical states. In particular we have shown new methods for preparing optomechani-cal pure states, squeezed states and entangled states. At the same time, proce-dures for experimentally detecting these quantum effects have been proposed. In particular, a quantitative measure of non classicality has been defined in terms of the negativity of phase space quasi-distributions. An operational al- gorithm for experimentally estimating the non-classicality of quantum states has been proposed and successfully applied in a quantum optics experiment. The research has been performed with relatively advanced mathematical tools related to differential equations with periodic coefficients, classical and quantum Bochner’s theorems and semidefinite programming. Nevertheless the physics of the problems and the experimental feasibility of the results have been the main priorities. / Die vorliegende Arbeit besteht aus verschiedenen theoretischen Untersuchungen von optomechanischen Systemen, das heißt physikalische Bauteile bei denen mechanische Freiheitsgrade mit Lichtmoden in optischen Kavitäten gekoppelt sind. Diese optimechanischen Wechselwirkungen, die über den Strahlungsdruck vermittelt werden, lassen sich zur Kühlung und Kontrolle von mechanischen Resonatoren im Quantenregime verwenden. Das Ziel dieser Arbeit ist es, verschiedene neue Ideen für Methoden vorzuschlagen, mit denen sich mesoskopische mechanische Systeme (bestehend aus etwa 10^15 Atomen) in sehr nicht-klassischen Zuständen präparieren lassen. Außerdem werden Techniken beschrieben, mit denen sich diese Quateneffekte experimentell beobachten lassen. Insbesondere wird ein quantitatives Maß für Nichtklassizität auf der Basis von Quasiwahrscheinlichkeitsverteilungen im Phasenraum definiert und ein operationeller Algorithmus zu dessen experimenteller Beschrieben, der bereits erfolgreich in einem quantenoptischen Experiment eingesetzt wurde.