Search

Abstract: When a photon experiences a change in momentum of any form, be it being absorbed or reflected from a surface, the photon will exert a force upon that material. This force is called the radiation pressure force. One way that we can harness this radiation pressure force is to couple optical and mechanical systems together to form optomechanical systems. One such optomechanical system is the optomechanical crystal (OMC), which consists of an optical waveguide patterned periodically with holes. By placing a defect, in other words by modifying the shape of the holes, in the center of the pattern we can form an optical cavity between the two end regions of the waveguide. This optical mode within the OMC can then excite a mechanical breathing mode in the center of the waveguide through the radiation pressure force. Optical fiber networks typically use light with wavelengths in the range of 1260 to 1625 nm (184 to 238 THz) since these wavelengths minimize optical loss within the fiber. In order for the OMC to be resonant with light of this wavelength the OMC must be of similar size, limiting our geometry to the micrometer scale. Fortunately there exist many different techniques, such as electron beam lithography and reactive ion etching, which allow for fabrication of devices this small. In this work, we describe our methods for designing, fabricating, and measuring an OMC made from silicon nitride. Designing the OMC was done through simulation of the optical and mechanical modes using COMSOL Multiphysics. The OMCs were then fabricated at the NanoFAB Fabrication and Characterization Center at the University of Alberta. Light was coupled into the OMC using a dimpled-tapered fiber setup, then measurements of the optical and mechanical properties were done using either a direct detection scheme or a balanced homodyne phase detection scheme. The final device supported an optical mode at 1482.55 nm and a mechanical mode at 2.62 GHz with an optomechanical coupling rate of 98.66 kHz.

This thesis presents experimental work on using cavity optomechanics techniques to control the motion of levitated nanoparticles in high vacuum. The motivation behind this work was to develop quantum mechanics experiments at room temperature with increasingly large masses. Research on levitated nanoparticles started with the development of optical tweezers by Arthur Ashkin in the 1970s. Ashkin himself highlighted the outstanding mechanical isolation of levitated nanoparticles in vacuum. Cavity optomechanics, on the other hand, concerns itself with the coupling of an optical resonator (a cavity), and mechanical motion. Among the applications of cavity optomechanics are the use light to measure and control mechanical motion. In the experiments presented here, we couple the motion of a nanoparticle to the field of a deeply resolved-sideband cavity (Ω ≈ 10 · κ) using optomechanical interaction, by either actively driving the cavity or using the coherent scattering configuration. In a first experiment, we show that laser phase noise heating poses an important technical obstacle in cooling the motion of levitated nanoparticles through optomechanical interaction if the cavity field is driven through one of the cavity mirrors. With the demonstration of the coherent scattering technique, and its more favorable performance to phase noise, we performed experiments using this technique and show optomechanical strong coupling of the motion of levitated nanoparticles. Finally, we discuss the use of narrow linewidth cavities for similar experiments and find that they hinder both cooling, by means of strong coupling, and detection, by means of optical filtering, of the mechanical motion.

Over the past decades, levitated nanoparticles have emerged as a versatile platform for scientific research, offering a high degree of control over the motional degrees-of-freedom of these comparably massive objects. Their properties make them outstanding force sensors, thanks to which they have found uses in many research applications, from studies of statistical mechanics to ultrafast rotation experiments. For these same reasons, they are excellent candidates for studying macroscopic quantum mechanics. In fact, levitated nanoparticles have already been brought to their quantum mechanical ground state of motion. However, optical traps are not well-suited for studying these quantum states, since they continuously measure the particle's position, collapsing the wave function in the process. We can address this shortcoming by introducing a secondary trapping mechanism that doesn't suffer from the same limitations. One obvious candidate are Paul traps, which have a proven track record in ion trapping. These rely on electric forces to maintain a particle in levitation. While less suited for initializing a particle in a quantum state, they are better suited for letting a quantum state evolve without destroying it. In this Thesis, we take the first steps towards this goal by implementing a hybrid Paul-optical trap. We describe the setup, its capabilities and its use cases. We then use the setup to do a proof-of-concept experiment, where we rapidly transfer the particle between traps, expanding the particle's (classical) position variance. With this research, we lay the groundwork for future, genuine macroscopic quantum mechanical experiments.

Feedback control allows a wide range of systems to be stabilized to out-of-equilibrium states. In quantum systems, feedback control takes two forms: incoherent control, in which projective measurements are made of the system state and the measurement results are used to inform changes to the system Hamiltonian, bringing the system towards its desired state; and coherent control, in which the system is allowed to interact coherently with an auxiliary quantum system, such that Hamiltonian dynamics coherently drive the system of interest into its desired state.An ultracold atomic gas coupled to a high-finesse optical cavity offers a convenient testbed for both of these forms of quantum feedback. Light escaping from the cavity mode carries information about the state of the atomic sample; this information can be processed externally and used to inform changes to external magnetic fields, to trapping parameters, and to the amplitude or frequency of light used to pump the cavity, effecting changes to the system's Hamiltonian and driving the atoms towards a desired state. Meanwhile, the atomic sample continually exchanges information with the cavity field through coherent interactions; by treating the atomic sample as the system of interest and the light field as an auxiliary controller, a Hamiltonian can be engineered such that these coherent interactions drive the atomic sample towards a desired state without the need for any external control.In this dissertation, I will re-introduce the elder of the two atom–cavity experiments currently active in the Stamper-Kurn group at Berkeley—dubbed the E3 apparatus—and will describe how it can be used to examine quantum feedback. I will discuss two instances of this, in particular: a coherent quantum feedback system, in which the energy of the collective atomic spin is autonomously stabilized to a set point conditioned on the detuning of the pump light from cavity resonance; and an incoherent feedback system, in which light escaping from the cavity offers a real-time measurement of the number of atoms present in the cavity during evaporative cooling, which is then used to stabilize to a desired atom number. Along the way, I will discuss other interesting findings that have been made along the way, as well as techniques that we've found particularly useful.

Abstract: This thesis describes the theory, fabrication, and characterization of monolithic integrated membrane-in-the-middle (MIM) optomechanical Fabry-Perot resonators and elliptical birefringent Fabry-Perot optical resonators. Both types of devices were fabricated on a silicon wafer using a thin-film buckling self-assembly technique. The MIM optomechanical cavity work follows that of a previous student, who had developed a method for releasing a free-standing silicon nitride (SiN) membrane embedded in a buckled dome microcavity, by using a surface micromachining (sacrificial etching) approach. In the present work, an improved photolithography method and an improved PECVD recipe for SiN deposition were developed. Concurrently, a vacuum system was designed and constructed, enabling optical measurements to be performed under a vacuum environment. Finally, in-situ vacuum-sealing of the optical cavities was attempted by deposition of various ‘sealing’ layers such as parylene deposition, sputtering of Si/SiO2, and plasma enhance chemical vapor deposition (PECVD) of SiO2. While these attempts were not entirely successful, they did provide an important basis for future work. The fabricated optical cavities exhibited a finesse of ~ 500 at 1550 nm wavelength range. Furthermore, mechanical vibrational modes were observed with mechanical quality factor ~200 for fundamental resonant frequencies in the ~ 5MHz-15MHz range for different devices. For the elliptical cavities, buckled domes with a large difference in radius of curvature along the major and minor axis were realized through appropriate patterning of a low-adhesion layer. These birefringent optical cavities exhibit astigmatism (two nested sets of Hermite- Gaussian modes reflecting the two radii of curvature) and birefringence (slightly non-degenerate iii resonant wavelengths for polarization along the major and minor axes of the ellipse). The observed astigmatism and birefringence are in good agreement with the predictions of a vector- modified paraxial wave theory. The cavities exhibited finesse of ~ 250 at 1550 nm wavelength range and polarization-mode splitting of the fundamental mode by ~25 GHz.

Abstract: Magnetic spin waves (magnons) are promising building blocks in developing classical and quantum hybrid systems. Magnons can couple to numerous sub-systems, such as microwave and optical photons, superconducting qubits and phonons. However, the parametric interaction between magnons and low-frequency phonons has not been widely studied experimentally. To elucidate this, we examined theoretically and experimentally the interaction between gigahertz magnons and megahertz frequency mechanical modes hosted within small spheres of yttrium iron garnet.We developed a linear theory describing the complete magnomechanical interaction using standard quantum optics techniques. From this analysis, we predicted two dynamical backaction effects: the magnon-spring effect, a shift in the phonon frequency and magnomechanical damping of the phonon mode due to the radiation-pressure-like force imparted by the magnon. We also describe the critical triple-resonance condition, where particular interactions are resonantly enhanced by ensuring the phonon frequency matches the magnon-photon normal-mode splitting. Next, we designed and built a cavity magnomechanical system to test our theoretical predictions. As a result, we observe the magnon-spring effect for the first time and magnomechical damping and anti-damping of the phonon mode. Finally, we moved the experiment onto the baseplate of a dilution refrigerator, where we aim to continue to study the behaviour of magnomechanical systems in cryogenic environments.

Opto-mechanics is the convergence of optics and mechanics towards the understanding of novel physical phenomenon and the achievement of cutting edge applications. From the effects of radiation pressure on the study of gravitational waves in a LIGO to the study of the quantum mechanical ground state of a simple harmonic oscillator, opto-mechanics spans a very wide range of the physical world. Optical systems with their capability of high sensitivity have been evaluated for applications as sensors like heart rate monitors, gas sensors and LIDARs. There has also been a growing demand for more robust, sensitive, low cost and easy to integrate gyroscopes for applications ranging from defense to autonomous driving. While there are existing technologies for high performance gyroscopes like the ring laser gyroscope and the machined hemispherical resonator gyroscope, these can be large, expensive and unwieldy rendering them unsuitable for a wide variety of applications. MEMS based gyroscopes are low-cost, come in smaller packages and are easy to integrate into systems but they might not have the high performance desired in these new demanding applications. Opto-mechanics has the potential to bridge the gap by combining MEMS and optics to leverage the high sensitivity of optics with the low cost and ease of integration of MEMS devices. The work presented in this thesis showcases some of the fundamental technologies needed for an opto-mechanical gyroscope (OMG). First is the \(\mu m\) scale hemispherical opto-mechanical resonator that is meant to incorporate the highly desirable mechanical properties of the cm scale hemispherical resonator gyroscope. These silicon dioxide resonators were fabricated in a MEMS centric process flow. The mechanical modes were optically sensed with a tapered optical fiber coupled to a toroidal optical cavity fabricated on the lip of the hemispherical resonator. Next is the development of silicon opto-mechanical wineglass mode resonators with on-chip waveguides. The silicon-on-insulator (SOI) platform employed here allows for better integration of the electro-static actuation and opto-mechanical sensing of the wineglass modes. The two orthogonal n=2 wineglass modes can be used for gyroscopy. Here, I first present the path towards closing the loop on the gyroscope drive wineglass mode. The differential electro-static actuation scheme achieved an 18db relative suppression of the undesired radial mode relative to the wineglass mode. The differential opto-mechanical sensing achieved a 5.4db enhancement of the drive wineglass mode detection and a further 11dB attenuation of radial mode. The suppression of the spurious modes relative to the desired wineglass mode allows a path for closing the oscillator loop on the wineglass mode without the need for additional filters. Next, I present the electro-static actuation of the drive wineglass mode and the opto-mechanical sensing of the orthogonal sense wineglass mode around 22MHz. The resonator was specially designed to achieve a controlled frequency mismatch between these two wineglass modes of only 120KHz and the design allows for tuning this further as needed. Measurements in vacuum showed an optical Q of 61,000 for the optical ring cavity mode and a mechanical Q of 11,500 for the drive wineglass mode and 7,670 for the sense wineglass mode. Last is the work with Lithium Niobate (LN) resonators. LN is of interest for its piezoelectric properties where the large piezoelectric coupling coefficient (\(k_t^2\)) allows for efficient electrical actuation of its mechanical modes. There is a potential for leveraging the high efficiency mechanical mode actuation to actuate the drive mode of a gyroscope device. Typically these resonators are actuated with gold but gold has been found to be mechanically lossy. Aluminum was chosen to be the replacement of gold in this work for its lower mechanical losses compared to gold. However, aluminum is very reactive with hydrofluoric acid (HF) which is used as part of the fabrication process of these devices. This necessitated an exploration of passivation methods to protect the aluminum electrodes from HF. Among the various films that I evaluated, a protective film called ProTEK PSB was found to be the most promising in resisting HF while protecting the aluminum electrodes. ProTEK PSB also had a process for its removal after the HF processing. In summary, this work presents some of the fundamental technologies such as a \(\mu m\) scale high mechanical performance device, a chip scale platform for selective transduction of the wineglass modes and a path towards high efficiency actuation of mechanical modes, all of which could contribute towards building an opto-mechanical gyroscope.

Optically levitated nanoparticles exhibit a measurable response to extremely minute forces. Examples include fluctuations introduced by thermal baths, and the stochastic recoil imparted by scattered photons. This high force sensitivity, together with the ability to measure the position with a precision close to the Heisenberg limit, makes this technology an outstanding platform for studying statistical mechanics, and for testing macroscopic quantum mechanics. In the first half of this Thesis, we engineer the stochastic properties of the thermal bath surrounding the particle. In a first experiment, these engineered fluctuations mimic a propulsive force with randomly precessing orientation. We then trap the nanoparticle in a bistable potential, and study the impact of this propulsive force on the transition rate. In a second experiment, we introduce a time dependence in the strength of the fluctuations. This technique mimics sudden changes in the temperature of the surrounding gas, and we use it to demonstrate nontrivial equilibration paths in the potential energy of the position. In the second half of this Thesis, we turn our attention to the role played by quantum fluctuations in our system. In a first experiment, we perform quantum state tomography of a particular optical mode into which the particle scatters. We demonstrate squeezing of this mode below the vacuum level, a consequence of the optomechanical interaction between light and particle. In a second experiment, we implement sudden jumps in the power of the trapping laser. We use these sudden jumps to show preliminary results towards coherent expansion of the motional wavefunction. This expansion represents a step closer towards generating a macroscopic quantum state of the motion of the particle.

Levitated micro- and nanoparticles have taken the stage as rich platforms for developing force sensors, and to study the classical to quantum transition of macroscopic objects. Optimal particle position detection has lead to exceptional control over its translational motion. More recently, researchers have extended the platform of levitated particles by addressing the rotational degrees of freedom. Manipulating rotational motion ranges from rotating a nanoparticle at ultrahigh speeds to feedback cooling its rotation from room temperature down to a few Kelvin. Both extremes show great potential for studying fundamental physics or enabling the development of highly sensitive sensors. In this thesis, we describe the interaction of light with an optically levitated nanodumbbell, formed by two nanospheres. The orientation of nanodumbbell couples to the polarization of the light beam, allowing for optical detection and control, while also interacting with a thermal bath of gas molecules. We initially demonstrate that the translational motion destabilizes the rotational motion, which we negate by feedback cooling the center-of-mass motion. In a circularly polarized beam, the nanodumbbell becomes a free rotor and is driven to high rotation frequencies. We study the fluctuations of the rotation frequency and demonstrate that those fluctuations are dominated by the coupling to the thermal bath. Besides optically driving the nanodumbbell, we also study and manipulate the nanodumbbell whilst constricting its orientation, creating so-called libration motion. More specifically, we feedback cool a libration mode to record-low temperatures and show evidence of its heating rate being dominated by radiation torque shot noise. Finally, we use theoretical insights to improve the optical detection scheme for the particle orientation, leading to a remarkable increase in signal-to-noise ratio.

After pioneering work on optically levitated particles in the 1970s by Ashkin, so called optical tweezers have not only become a popular tool in biology and medicine but also experienced a renaissance in vacuum trapping over the last ten years. While the broader field of optomechanics already gained popularity previously and investigated the classical-to-quantum transition in cryogenic systems at the beginning of the last decade, levitated particle optomechanics opened the door to room temperature quantum experiments. The versatile levitated particle system has been utilized in various applications, such as rotation experiments at world record speeds exceeding 6 GHz, highly sensitive force sensors or to study stochastic effects of thermodynamics. Most intriguing, however, was the transition into the quantum regime by ground-state cooling of the particle's center-of-mass motion in one dimension, setting the first milestone of genuine quantum experiments. Ten years after the first cooling attempt, a technique adopted from the atom and ion cooling community finally led to ground-state cooling of a levitated particle. This technique, called cooling by coherent scattering, is the central scheme of this thesis. In the first part of this thesis we describe the construction of a double vacuum chamber system to efficiently trap and transfer a levitated particle into an optical cavity. In contrast to previous systems, no particle transfer to a second tweezer is necessary, minimizing the risk of particle loss and enabling experiments within minutes after particle loading. In the second part, we present the working principle of our coherent scattering setup. It was the first pure optical trapping configuration to transition a levitated particle into high vacuum, while being stabilized exclusively through cavity cooling. At the time, we achieved record low cavity cooling center-of-mass energies reflected by an effective temperature of a few millikelvin and demonstrated genuine 3D cooling of the motional degrees of freedom. The central feat of the coherent scattering setup is the ability to cool the particle motion in a cavity field node, reducing the impact of laser phase noise compared to the dispersive regime. In the last part of the thesis, we find that the mechanical instability of the particle position limits the suppression of phase noise, leading to particle cooling to about 10 phonons.

Accurate determination of attitude and position is a fundamental aspect of inertial navigation. Modern navigation techniques use a combination of sensors, that rely on an Inertial Measurement Unit (IMU) for short term position estimation and at least one constellation of the Global Navigation Satellite System (GNSS), such as the Global Positioning System (GPS), to reduce long term solution divergence. However, for earth and space applications, in GNSS denied environments, the performance of IMUs, and of their core accelerometers, is critical for the success of the mission. In fact, improvement in accelerometer’s bias stability and resolution can enable longer autonomous navigation vehicles, including satellites and spacecraft. At the same time, reductions in size and weight are key factors for longer range and extended mission duration.However, scaling down the dimensions of transducers that depend on their weight to harvest specific force is not an easy task, since reduction in mass is proportional to the cube of the length (~ l 3). A smaller transducer needs to be more sensitive to motional displacements, if it were to maintain the same performance, which translates into an operational point closer to the physical limits. In this regard, recent advances in radiation-pressure driven cavity optomechanics have provided new frontiers in laser cooling of mesoscopic systems, chip-scale stable RF sources, phonon lasers, and chaos. By coupling optical and mechanical modes, it is possible to detect tiny mechanical motions in the order of a few femtometers, which has attracted interest for sensing design on accelerometers and other transducers, and has enabled applications such as the detection of gravitational waves. In our work, we propose an optomechanical accelerometer that in contrast to state-of-the-art piezoelectric or capacitive accelerometers, offers an integrated feedback system and optical readout, which provides advantages like narrow-linewidth, high-sensitivity laser detection, with low-noise resonant optomechanical transduction close to the thermal limit, and can be used to measure atto-Newton level forces through detecting femtometer displacements. This technique will enable the development of more sensitive accelerometers and gravimeters that will improve position determination.

Dissipation is an inevitable property of a mechanical system and influences the dynamical behavior and device performance. It is, therefore, crucial to study and understand the sources of dissipation in mechanical systems in order to control the dissipation present in the system. These sources of dissipation can be broadly classified in two groups: extrinsic and intrinsic mechanisms. Extrinsic mechanisms are independent of material properties and influenced by the external properties of the system, such as geometry, pressure, and temperature. Intrinsic mechanisms on the other hand, are independent of external conditions and arise from the intrinsic properties of the device material, such as defects in the bulk and the surface of the material. In this work, we closely study two extreme limits of dissipation at the opposite ends of the spectrum. First, at the high dissipation limit where extrinsic mechanisms dominate dissipation, spectral properties of the thermal noise force giving rise to Brownian fluctuations of a continuous mechanical system — namely, a doubly clamped nanomechanical beam resonator — immersed in a viscous liquid are investigated. To this end, two separate sets of experiments are performed. The power spectral density (PSD) of the Brownian fluctuations of the resonator around its fundamental mode are measured at the center of the resonator. Then, the frequency-dependent linear response of the resonator is measured, again at its center, by driving it with a harmonic force, via an electrothermal transducer, that couples well to the fundamental mode. These two separate measurements are then used to determine the PSD of the Brownian force acting on the structure in its fundamental mode. The PSD of the force noise extracted from multiple resonators with varied lengths spanning a broad frequency range displays a ``colored spectrum'' and follows the viscous dissipation of a cylinder oscillating in a viscous liquid by virtue of the fluctuation-dissipation theorem. In the second application, which is at the ultra-low dissipation limit at low temperature where intrinsic mechanisms dominate dissipation, we design and fabricate high-frequency aluminum nitride (AlN) piezo-optomechanical resonators. Furthermore, an acoustic radiation shield consisting of periodic phononic crystals is designed and implemented to further decrease dissipation. Fabrication and design of both the optomechanical cavity and phononic crystals are discussed in detail. Room temperature characterization of the ring resonator is presented and out-of-plane thickness mode of the AlN resonators has been identified. With microwave mechanical frequency and high Quality factor mechanical response, these resonators can be cooled down to quantum ground state with direct cooling methods such as dilution fridge cooling. These type of resonators can achieve efficient conversion between electrical, optical, and mechanical signals which can be utilized for quantum information science and sensing applications in the field of nanoelectromechanical systems.

Abstract: This thesis describes the theory, fabrication, and characterization of on-chip, integrated Fabry-Perot microcavities embedded with thin silicon nitride membranes. The approach combines a previously developed process for fabricating self-assembled Si / SiO2 / Ta2O5 curved mirror cavities, with a XeF2-based sacrificial etch process to allow for free standing PECVD silicon nitride membranes to be released internally. Membranes with a fundamental mechanical resonant frequency ~ 10 MHz were coupled to wavelength-scale cavities operating in the ~ 1550 nm wavelength range, and the optical and mechanical properties of the combined system were studied. The estimated optomechanical coupling coefficient g0 / 2 pi ~ 0.1 MHz is significantly higher than that previously reported in membrane-in-the-middle systems. In further contrast to previous approaches, the work here presents a scalable and monolithic surface-micromachining process for systems that are otherwise typically large and complex. These devices are also described within the context of existing cavity optomechanics literature. The small size and high areal chip density of these devices may allow them to serve as potential candidates in a variety of applications such as sensing, frequency transduction, and quantum information.

Abstract: Wavelength transduction of light, specifically between the microwave and telecom regimes, has received a great deal of attention from the cavity optomechanics community as a landmark application for optomechanical systems. Mechanical systems are uniquely suited to wavelength transduction, as photon-phonon momentum transfer allows mechanical motion to couple to light throughout the electromagnetic spectrum. The use of cavities to contain both electromagnetic and mechanical energy in resonators allows for enhanced interaction between light and matter, creating a viable path to high efficiency energy conversion. For a device to act as an ideal transducer, it must satisfy three key parameters: low-noise, high-efficiency, and coherence. In this work we explore gallium arsenide optomechanical crystals as a candidate for microwave-to-telecom wavelength transduction, tackling the basic characteristics of the devices as optomechanicalresonators and profiling their noise and efficiency characteristics. To demonstrate transduction efficiency and coherence, we combine the optomechanical crystals with a 3D microwave cavity, and use the piezoelectric properties of gallium arsenide to couple the microwave mode to the gallium arsenide mechanical mode. By injecting a signal into the microwave cavity and measuring it using the gallium arsenide telecom mode, we demonstrate microwave-to-telecom transduction and measure both the efficiency and the coherence of the transducer. To demonstrate the low-noise capabilities, we use a dilution refrigerator to cool the optomechanical crystal to a temperature on the order of 10 mK, where we show that the mechanical mode is in the ground state with an average thermal phonon population below one. For the transduction protocol described in this thesis, a ground state mechanical resonator is critical to low-noise transduction, as thermal phonons are transduced in the same way as signal phonons and become added signal at the output of the transducer. We use these low-temperature measurements to estimate the number of added noise photons in a transduced signal. These experiments are the foundation upon which future microwave-to-telecom transduction experiments in the Davis lab will be predicated. The methods described in this thesis, particularly the gigahertz optomechanics measurement techniques and apparatus, will act as a guide to future students who pursue the ultimate goal of transduction: the entanglement of superconducting qubits through a telecom link.

Quantum states of light with a fixed number of photons are useful for several quantum optical technologies. In this thesis, we theoretically study single-photon generation in a three-mode optomechanical cavity with a Kerr type nonlinear medium. We begin by presenting a detailed derivation of the master equation under Born-Markov approximations describing the dissipative dynamics of our setup. Next, we concentrate on two system parameters, the three-mode coupling rate (g) and the strength of the Kerr nonlinearity (U) and analyze the detuning (Δ) dependence of the second-order correlation function g(2) to determine the photon statistics. As a key finding, we analytically conclude that the system can exhibit UPB for a wide range of detunings even with weak nonlinearities by adjusting the three-mode coupling. For instance, we find that the condition g(2) (0) < 1 can be met with fixing U== 0.69k and 푔 = 2k while κ here represents the optical mode decay rate. Moreover, we observe that the minimum of g(2) (0) shifts to higher detunings with increasing three-mode coupling rate and decreasing the Kerr nonlinear strength. With the current advancements in hybrid optomechanics, this work is experimentally feasible and can provide an alternate method for single-photon generation without relying on stringent conditions of CPB.

About a decade ago, optically levitated nanoparticles have been proposed for macroscopic tests of quantum mechanics. For such tests, the thermal motion of the particle’s center of mass is required to be close to its ground state of energy. Ever since these proposals, research groups around the world try to achieve ground-state cooling of optically levitated glass particles. In this dissertation, we cool the center-of-mass motion of a nanoparticle in an optical trap. Based on the position measurement of the particle, we apply a damping force in proportion to the particle’s speed, which leads to a cooling effect. We find that the cooling performance of our cold damping scheme is limited by the measurement imprecision. We analyze our detection principle theoretically and find an ideal detection scheme whose imprecision is at the fundamental noise level dictated by quantum mechanics. Such a Heisenberg-limited detection would, in principle, allow for ground-state feedback cooling. With these insights applied to our experiment, we cool the motion of our particle to an average of four quanta. Moreover, we resolve an asymmetry between the Stokes and anti-Stokes scattered light from the particle. This quantum effect allows us to calibrate the system to the ground state energy. Our work advances the research field of levitated optomechanics toward quantum control and therefore toward macroscopic tests of quantum mechanics.

This thesis begins with the introduction of optomechanics, the study of the interaction between light (photons) and mechanical oscillations (phonons) using bulk 3-D cavities. The description of 3-D microwave cavities is introduced as the boundary of the electromagnetic field and the mathematics are developed for the interaction between the electromagnetic field and a fluctuating boundary (mechanical oscillator). This work was established in pursuit of observing optomechanical effects within macroscopic 3-D cavity systems.Three main microwave 3-D cavity geometries were used for this work: cylindrical, re-entrant, and coaxial quarter-wave (λ/4) cavities. A large number of cavities were made by the author in a machine shop in an attempt to develop strongly-coupled optomechanical systems. The pursuit of this goal led to the first observation of strain engineering, or dissipation dilution, via the thermal Casimir effect and its exciting potential applications.The noteworthy projects that saw success in this work were the development of tunable, superconducting microwave cavities using a lossless, non-contacting fashion in addition to the ground-up progression of re-entrant cavities that led to the first observation of the thermal Casimir spring and dilution effect at room temperature. The outcome of this work opens the doorway for the development of “in situ” arbitrary, topological resonators with the added benefit of an increased mechanical quality factor Qm due to heightened strain.

There are several unknown aspects about the decoherence mechanisms that cause thetransition of a system from the quantum to the classical regime. In this work we presentoptomechanical systems, in which light couples to mechanical motion, as a suitable platformfor the study of decoherence in macroscopic systems.We start by discussing some of the features of optomechanical systems, focusing onthe membrane-in-the-middle configuration. We then explain how optomechanical systemscan be extended to include multiple modes, which enables different state transfermechanisms, and we show an experimental demonstration of two such transfer schemes.We also explain how multimode systems can exhibit an enhanced optomechanical couplingrate for individual and collective mechanical modes.Later we introduce periodic structures and how they can be applied at different scalesin order to improve the performance of our optomechanical devices. We first analyze thevibrational modes of a thin membrane within the framework of linear elasticity andproceed to show how a phononic crystal reduces the dissipation of mechanical energy inthe membrane. Next, we investigate an interference model for how a photonic crystalcan enhance the reflectivity of a membrane for out-of-plane propagating radiation. Wemove on to outline the fabrication process for our optomechanical membrane devices.We conclude with a theoretical proposal for a measurement of decoherence in a macroscopicsuperposition state. This proposal relies on the state transfer techniques discussedearlier and should be possible to implement with current technologies.

Abstract: This thesis describes the design, fabrication, and characterization of 3D superconducting microwave cavities for two applications. It first describes a cryogenically compatible microwave filter that is able to tune its resonant frequency by an unprecedented 5 GHz via deformation caused by a a helium pressure vessel. Then, it describes a novel microwave optomechanics device where such a cavity is coupled to an aluminized SiN membrane. It demonstrates that this device can be back-action cooled from the 450 mK base temperature of the cryostat down to 160 mK.

Abstract: Coupling optical cavities to freely moving mechanical devices results in optomechanical systems. Enabled by advancing fabrication techniques, optomechanical systems are now easily fabricated using silicon-on-insulator chips at the micro- and nanoscale. These nano-optomechanical systems (NOMS) combine nanomechanical devices with photonic integrated circuits for sensitive readout of mechanical displacement. NOMS have many potential applications, including mass detection. In this thesis, we work towards improving the dynamic range of cantilevers coupled to photonic circuits for mass sensing applications. We use an all-optical pump-and-probe approach. First, we derive and demonstrate a simple model for designing optomechanical systems for efficient actuation via the optical gradient force. We achieve large amplitudes of vibration and show the power required to achieve these amplitudes is nearly four times smaller than an unoptimized design. When driving the cantilever to large amplitudes, we observe multiple simultaneous nonlinearities. To understand the source of these nonlinearities, we derive and solve a numerical model that allows us to determine that there are three nonlinearities present in the system; a readout nonlinearity and two distinct optical force nonlinearities. The model is unique in that it incorporates the effect of the pump laser on the optomechanical system. Of all the nonlinearities, the readout nonlinearity is the most detrimental to mass sensing performance as it hinders our ability to determine the amplitude of the mechanical device. To mitigate the readout nonlinearity, we design a photonic integrated circuit to increase the linear range of NOMS readout. This photonic architecture successfully increases the linear range by a factor of four while maintaining the sensitivity of the previous design. These improvements increase the dynamic range, and therefore the limit of detection, by a factor of 2.8. The work presented here will help to improve the viability of NOMS mass sensors in a variety of applications, including portable health care diagnostic tools.

Realization of physical systems for quantum information processing fundamentally rests on the ability to generate entanglement among many quantum bits. To this end, solid state quantum systems are often considered a scalable approach due to the relative ease of generating of a large number of individual qubits. However, realizing strong coherent interactions that dominate decoherence processes in the solid state environment is a formidable challenge that has continued to motivate the investigation of new physical systems to store quantum information and new mechanisms to achieve controllable interactions. This thesis takes steps in these directions with diamond color centers, which can store optically accessible quantum information in their electronic spin. We study color center spins as acoustic two level systems, and consider whether their interaction with single phonons in diamond can be engineered to be coherent. Through spectroscopy of color centers in diamond nanomechanical devices and follow-up theoretical work, we identify the negatively charged silicon vacancy (SiV) color center as a promising candidate for phonon-mediated quantum information processing. In the process, an electromechanical device platform capable of tuning the strain environment of color centers is developed. It is used to mitigate thermal decoherence of the SiV spin and demonstrate photon-mediated quantum interference between two SiV centers on a diamond chip, highlighting the utility of nanomechanical devices for photonic quantum networks. Finally, we present high quality factor, wavelength scale acoustic resonators in diamond using phononic crystals towards a coherent interface between SiV centers and single phonons.

Detection, characterization and separation of chiral structures as one of the fundamental constituents of biomolecules are crucial in chemical and biological applications. Conventionally, chiroptical techniques such as circular dichroism (CD) are exploited to identify the material chirality. These methods require substantial amount of sample material with a high concentration. since chirality effect (as an indirect electric to magnetic coupling between incident light and sample material) is typically very weak. Therefore, the observation of chirality might be masked under the electric properties in chiroptical techniques if a substantial amount of material is not provided. Consequently, these techniques are not suitable for detection of chirality for nanoscale samples and can’t provide information about their primary or secondary structure. On the other hand, separation of enantiomers is of great interest in pharmaceutical applications. Classical separation techniques which are used to separate molecular compounds and complexes in achiral environment, such as liquid-liquid extraction, chromatography and distillation are not universal for separation of all types of chiral molecules/compounds since not all compounds and host media are chemically compatible. This dissertation focuses on introducing new techniques for detection, characterization and manipulation of chiral nanoparticles and nanostructures using structured light. Specifically, a new technique involving the measurement of photo-induced optical force (near-field characteristics) rather than the measurement of conventional scattered power (far-field characteristics) is introduced which substantially enhances the resolution in the detection of enantiomer type of chiral samples down to sub-100 nm. Furthermore, by utilizing structured illumination (circularly polarized wave for detection of transverse chirality and combination of azimuthally and radially polarized waves in the so-called azimuthally-radially polarized beam for detection of longitudinal chirality) the prediction of spatial features of the structure of a chiral sample is facilitated. It’s been demonstrated that circularly polarized illumination can’t differentiate between chirality and anisotropy. To overcome this deficiency and differentiate between anisotropy and chirality, an engineered combination of vortex beams (ARPB) is utilized. Lastly, a novel scheme to manipulate and control chiral nanoparticles and to sort enantiomers is proposed.

A quantum network consisting of computational nodes connected by high-fidelity communication channels could expand information-processing capabilities beyond those of classical networks. Superconducting qubits hold promise for scalable quantum computation at microwave frequencies, but must operate in an isolated cryogenic environment; meanwhile, quantum communication over long distances has been demonstrated with optical photons. A fast, quantum-coherent interface between the two would be a key element of a large-scale quantum network or distributed quantum computer.In this thesis, we describe the theoretical basis as well as the practical design and development of a device incorporating a silicon optomechanical nanobeam and an aluminum-nitride-based electromechanical transducer. We find that this class of device has the potential to approach ideal quantum microwave-optical transduction. Finally, we experimentally demonstrate classical, continuous-wave operation of such a device with internal conversion efficiencies above 1%. This device also has a larger bandwidth than previous efficient microwave-optical transducers, allowing us to operate in the time domain with 20 ns pulses.

Integrated photonics provide unique advantages in tailoring and enhancing optical forces. Recent advancements in integrated photonics have introduced many novel phenomena and exotic photonic media, such as photonic topological insulator, negative index material, photonic crystals, 2D material, and strongly-modulated time-dynamic systems. In my dissertation, I theoretically and numerically explore the novel properties and applications of optical forces in these systems. We propose guided-wave photonic pulling forces in photonic crystal waveguides. Photonic crystal waveguides offer great capability to define the mode properties, and can incorporate complex trajectories, leading to unprecedented flexibility and robustness compared to previous works in free space or in longitudinally uniform waveguides. With response theory, a virtual work approach, we establish general rules to tailor optical forces in periodic structures involved with photonic crystals: pulling forces arise from negative gradients in the phase responses of the outgoing modes, which corresponds to forward scattering on the Bloch band diagram with unit cell function corrections. We devise robust forward scattering, first, using topologically protected nonreciprocal chiral edge states, second, using backward (i.e. negative index) waves in a reciprocal system. The structures are tailored to accommodate only the necessary modes, which largely benefits the robustness. With these, we numerically demonstrate long range pulling forces on arbitrary particles through sharp corners. Our work paves the way towards sophisticated optical manipulation with single laser beam. We next explore the implication and applicability of momentum conservation in periodic media, which has been unclear due to the inhomogeneity and strong near field. We first quantify the linear momentum flux of Bloch modes under discrete translational symmetry, which is further understood from their plane wave composition. We then demonstrate through varies examples that the change in momentum flux predicts a total force distributed to both the scatterer and the media. However, one still need response theory to predict the forces on individual objects. Using response theory, we can predict more general forms of optical forces. We numerically demonstrate optical motoring effect due to singularity in the phase responses, and strong optical forces between graphene sheets due to large gradients in the phase responses. In particular, by combining the strong forces in graphene guided-wave system and the exceptional elastic properties of graphene, we can get an SBS gain that is four orders of magnitude stronger than in a silicon step-index waveguide, which may lead to smaller devices for RF signal processing.

Superconducting radio frequency (SRF) cavities present a unique opportunity in their potential for extremely large quality factors (Q) which allow for low-loss microwave systems which extend photon lifetimes. They have subsequently been used and improved upon as individual cells of particle accelerators where large accelerating voltages are required. More recently, they have been used as double SRF cavity systems for coupling electromagnetic fields via qubits inserted into the cavity bodies. Capitalizing on this Q enhancement, we propose an SRF cavity system for parametric amplification of these microwave fields from vacuum. This triple SRF cavity consists of a pump cavity with a silicon nitride (SiN) membrane acting as one end-wall and two signal/idler cavities that are separated by an iris plane. Parametric amplification occurs when some parameter of the system varies sinusoidally in time and this subsequently drives the system into oscillation. Here, we vary the length of the cavities by driving the SiN membrane end-wall into motion using the radiation pressure from the pump cavity. Sufficient energy transfer between cavities will allow amplification and subsequent oscillation of the vacuum fields. We will introduce and explain theoretical background, SRF cavity fabrication and testing, SiN membrane mechanics, and lastly double cavity mechanics. We will identify which facets of the project seem feasible at this time.

The quantum to classical transition in large mechanical systems is still a mystery. An ideal tool for exploring this new regime of physics is cavity optomechanics. The field of optomechanics uses light in an optical cavity to finely control and detect mechanical motion. Remarkable progress has been made in recent years with the generation of non-classical states of motion. If such states can be extended into the macroscopic regime, new physics may emerge due to the unprecedented scale.In this dissertation we work towards the goal of macroscopic quantum optomechanics by developing new mechanical devices, experimental techniques and experimental protocols. First we fabricate nested trampoline resonators, devices with high mechanical quality factor, excellent vibrational isolation from the mechanical environment and mirrors which can support high finesse cavities. With these devices we explore a new optomechanical interaction in which spatially separated, nondegenerate mechanical modes can exchange their state. Finally, we investigate theoretically how this interaction can generate a quantum entangled state between multiple mechanical modes, bypassing many experimental difficulties of previously proposed schemes. These developments help pave the way towards phonon interference experiments in macroscopic resonators.

Collagens and extra cellular matrix (ECM) proteins play important roles in the structural composition of tissues, and their modifications are implicated in diseases including cancer metastasis, tissue fibrosis, diabetic ulcers. Current tissue collagen analyses are based on destructive histological methods, whereas the ECM proteins’ intrinsic autofluorescences can provide a label-free detection and imaging to differentiate tissue compositions, modifications, and disease states. Fluorescence lifetime spectroscopy has been demonstrated as a key technique to distinguish ECM proteins in tissue. However, the large, expensive, and often operationally challenging instrumentation required to measure fluorescent lifetimes from tissues prevents the technique from gaining traction in biomedical applications.To this end, this thesis represents three major efforts to address this roadblock in tissue lifetime instrumentation by 1) demonstrate a facile fluorescence lifetime technique via frequency domain analysis, 2) realizing a hand-held multispectral lifetime probe for point detection on the skin, 3) realizing a low-cost, low complexity LED based imaging system to enable FLIM (fluorescence lifetime imaging microscopy) for histology without daunting instrumentation.In the first effort, the frequency domain (FD) fluorescence lifetime technique was demonstrated for the differentiation of collagens I/III and elastin, three major biophotonic components in wound tissues that undergo change during healing. In the second effort, a compact multispectral xsystem demonstrated the FD lifetime’s utility as a point-of-care device, and added additional wavelength-specific lifetime spectroscopy to further improve differentiation. The third effort expands theFD technique to an imaging modality, by leveraging LED scanning optomechanics to create histological images of tissues without labeling. Additionally, the scanning of a diabetic ulcer showed evidence that the technique can provide quantitative information on disease modification of the tissue that current immunohistochemical methods are ill-equipped to provide. By providing a quantitative, more nuance model of tissue biophotonics while using low-cost, low complexity FD instrumentation, the works in this thesis hopes to increase accessibility and popularity of label-free ECM lifetime spectroscopy for a number of biomedical and clinical applications.

This dissertation is organized into three parts. First, the design for a radio frequency fiber transmission line built out of a grid of micrometer-scale conductors embedded in an insulating polymer cladding is presented to mitigate the skin and proximity effects. By adopting a checkerboard out-of-phase current phasing scheme, the internal inductance of the line is significantly lower than in two-conductor lines and results in an LC bandwidth of approximately 2 GHz, with flat attenuation and linear phase dispersion. The device performance is characterized in terms of its geometric degrees of freedom and a fabricated prototype is presented. Second, the kinetic inductive and plasmonic response of monolayer graphene in the terahertz spectrum is examined in the context of several important applications. The dispersive responses of two-dimensional graphene and three-dimensional copper transmission lines are compared to map the dispersive signaling performance in terms of transmission line cross-sectional size. This demonstrates a surprisingly broadband LC response with flat attenuation in nano-scale lines. This kinetic inductive response of graphene is demonstrated to miniaturize the photonic band structure of a photonic crystal slab where an in-plane periodicity of 300 nm has its photonic band gap in the terahertz spectrum. The sub-diffraction photonic band structure resembles that of the two-dimensional photonic crystal, supporting a wide photonic band gap in extremely thin slabs. The viability of graphene for cavity optomechanics is analyzed from near infrared to terahertz wavelengths, demonstrating a large optomechanical coupling, on the order of 3D optomechanical materials. Third, a class of nonreciprocal devices is proposed based on coupling to the sideband states, called Floquet resonances, that arise in temporally modulated optical resonators. The degrees of freedom in the modulating waveform tailor the energy exchange and phase of the Floquet resonances to realize unique nonreciprocal spectral responses in compact devices. We examine optical scattering from Floquet resonators coupled to narrowband waveguides using temporal coupled-mode theory. A three-port circulator is built out of a cascade of Floquet resonators to demonstrate broadband forward transmission and ideal isolation for dual-carrier waves. Full-wave numerical simulations in the coupled frequency domain demonstrate the circulator in an on-chip photonic crystal platform

Micro- and nano-mechanical resonators with low mass and high vibrational frequency are often studied for applications in mass and force detection where they can offer unparalleled precision. They are also excellent systems with which to study nonlinear phenomena and fundamental physics due to the numerous routes through which they can couple to each other or to external systems. In this work we study the structural, thermal, and nonlinear properties of various micro-mechanical systems. First, we present a study of graphene-coated silicon nitride membranes; the resulting devices demonstrate the high quality factors of silicon nitride as well as the useful electrical and optical properties of graphene. We then study nonlinear mechanics in pure graphene membranes, where all vibrational eigenmodes are coupled to one another through the membrane tension. This effect enables coherent energy transfer from one mechanical mode to another, in effect creating a graphene mechanics-based frequency mixer. In another experiment, we measure the resonant frequency of a graphene membrane over a wide temperature range, 80K - 550K, to determine whether or not it demonstrates the negative thermal expansion coefficient predicted by prevailing theories; our results indicate that this coefficient is positive at low temperatures -- possibly due to polymer contaminants on the graphene surface -- and negative above room temperature. Lastly, we study optically-induced self-oscillation in metal-coated silicon nitride nanowires. These structures exhibit self-oscillation at extremely low laser powers (~1uW incident on the nanowire), and we use this photo-thermal effect to counteract the viscous air-damping that normally inhibits micro-mechanical motion.

Throughout the last century, scientists have been trying to understand the peculiar behavior of microscopic objects such as electrons, atoms, ions, and molecules. This behavior is predicted by quantum mechanics. Especially surprising is that the laws of the quantum world contradict our expectations from classical mechanics. Therefore, it is a central question in quantum physics how the transition between these two regimes materializes. In this thesis, we address this fundamental question using a dielectric nanoparticle levitated in an optical focus in vacuum. This is a promising system for studying quantum mechanics with mesoscopic objects. We measure the internal temperature of this nanoparticle that fundamentally limits the lifetime of a quantum state of the center-of-mass motion. To do that, we study the dynamics of the particle's center-of-mass motion depending on the internal particle temperature. The second goal of this thesis is to perform a free-fall experiment with a levitated nanoparticle. This is a first step towards time-of-flight state tomography and quantum interferometry experiments with nanoparticles. By switching the optical trap off and back on, we achieve a repeatable free fall of the particle. We use this method to measure the initial energy of the particle motion before the free fall and demonstrate ultra-sensitive detection of static forces in the attonewton regime.

Optomechanics explores the coupling between light and the mechanical motion of nanoscopic matter. Optical levitation offers a promising avenue in the investigation of macroscopic quantum behavior by using glass nanoparticles that are physically detached from the environment. Our goal in this thesis is to bring a levitated nanoparticle to the quantum ground state of its center-of-mass motion using phase-sensitive feedback that is conditioned on high precision interferometric measurements of the particle's position. We cool the harmonic motion of the nanoparticle from ambient to microkelvin temperatures and measure its reheating rate under the influence of the radiation field. The limit reached corresponds to that of photon recoil heating, which will set bounds to the coherence times of future quantum states and protocols in our system. We quantitatively characterize the role of laser intensity noise for demanding applications in ultrasensitive force detection and find that the system is in the regime of strong measurement backaction. Finally, protocols to interrogate the classical to quantum transition are proposed.

A fully functional quantum computer must contain at least two important components: a quantum memory for storing and manipulating quantum information and a quantum data bus to securely transfer information between quantum memories. Typically, a quantum memory is composed of a matter system, such as an atom or an electron spin, due to their prolonged quantum coherence. Alternatively, a quantum data bus is typically composed of some propagating degree of freedom, such as a photon, which can retain quantum information over long distances. Therefore, a quantum computer will likely be a hybrid quantum device, consisting of two or more disparate quantum systems. However, there must be a reliable and controllable quantum interface between the memory and bus in order to faithfully interconvert quantum information. The current engineering challenge for quantum computers is scaling the device to large numbers of controllable quantum systems, which will ultimately depend on the choice of the quantum elements and interfaces utilized in the device. In this thesis, we present and characterize a hybrid quantum device comprised of single nitrogen-vacancy (NV) centers embedded in a high quality factor diamond mechanical oscillator. The electron spin of the NV center is a leading candidate for the realization of a quantum memory due to its exceptional quantum coherence times. On the other hand, mechanical oscillators are highly sensitive to a wide variety of external forces, and have the potential to serve as a long-range quantum bus between quantum systems of disparate energy scales. These two elements are interfaced through crystal strain generated by vibrations of the mechanical oscillator. Importantly, a strain interface allows for a scalable architecture, and furthermore, opens the door to integration into a larger quantum network through coupling to an optical interface.There are a few important engineering challenges associated with this device. First, there have been no previous demonstrations of a strain-mediated spin-mechanical interface and hence the system is largely uncharacterized. Second, fabricating high quality diamond mechanical oscillators is difficult due to the robust and chemically inert nature of diamond. Finally, engineering highly coherent NV centers with a coherent optical interface in nanostructured diamond remains an outstanding challenge. In this thesis, we theoretically and experimentally address each of these challenges, and show that with future improvements, this device is suitable for future quantum-enabled applications. First, we theoretically and experimentally demonstrate a dynamic, strain-mediated coupling between the spin and orbital degrees of freedom of the NV center and the driven mechanical motion of a single-crystal diamond cantilever. We employ Ramsey interferometry to demonstrate coherent, mechanical driving of the NV spin evolution. Using this interferometry technique, we present the first demonstration of nanoscale strain imaging, and quantitatively characterize the previously unknown spin-strain coupling constants. Next, we use the driven motion of the cantilever to perform deterministic control of the frequency and polarization dependence of the optical transitions of the NV center. Importantly, this experiment constitutes the first demonstration of on-chip control of both the frequency and polarization state of a single photon produced by a quantum emitter. In the final experiment, we use mechanical driving to engineer a series of spin ``clock" states and demonstrate a significant increase in the spin coherence time of the NV center. We conclude this thesis with a theoretical discussion of prospective applications for this device, including generation of non-classical mechanical states and spin-spin entanglement, as well as an evaluation of the current limitations of our devices, including a possible avenues for improvement to reach the regime of strong spin-phonon coupling.

High-quality-factor optical microresonators have emerged as a verstatile tool in studying light-matter interactions and their technological applications. They have proven to be particularly efficient sensors by transducing weak interactions, such as a minuscule change in effective refractive index, into a large optical output signal, when interrogated near their resonance frequencies. Their large quality factors and small sizes also lead to a build-up of large optical forces within the devices. These forces are a driver of high-quality mechanical oscillations of the optical resonator. The resolution of accelerometers is limited by fundamental thermomechanical noise and by extra noise added by the readout mechanism. We present a platform based on SiN optical microresonators with a high quality factor (Q), which can be used as highly sensitive displacement sensors to minimise readout noise in accelerometers. In addition, we demonstrate integration of SiN micromechanical resonators, which also potentially demonstrate very high quality factors, with a large micromachined mass, which can be used to lower thermomechanical noise in accelerometers. The SiN ring resonator with the SiN micromechanical resonators together can potentially measure acceleration with nano-g resolution over a broad bandwidth. Frequency-locking between mechanical oscillators is of scientific and technological importance. However, existing schemes to observe such behaviour are not scalable over distance. We demonstrate a scheme to couple two independent mechanical oscillators, separated in frequency by 80 kHz and situated far from each other (3.2 km), via their optomechanical interactions. Using light as the coupling medium enables this scheme to have low loss and be extended over long distances. Delay-coupled oscillators exhibit unique phenomena that are not present in systems without delayed coupling. We experimentally demonstrate mutual synchronisation of two free-running micromechanical oscillators, coupled via light with a total delay 139 ns (approximately four and a half times the mechanical oscillation time period). This coupling delay induces multiple stable states of synchronised oscillations, each with a different oscillation frequency. These states can be accessed by varying the coupling strengths. This result could enable applications in reconfigurable radio-frequency networks, and novel computing concepts.

An optomechanical resonator can greatly enhance the coupling between optical and mechanical waves within the resonator. Therefore, unlike most of optical sensors, optomechanical sensors can optically interrogate mechanical properties of samples including liquids. This thesis discusses the development of two types of novel optomechanical sensors using capillary-based microfluidic ring resonators: 1) Microfluidic sensor using optomechanical vibration to optically monitor the mechanical properties of liquid samples; and 2) Pressure sensor that can remotely detect air-coupled ultrasound waves. In microfluidic optomechanical sensor development, we used silica-based microfluidic ring resonators to optically generate mechanical vibrations up to 140 MHz with liquids inside the resonators. We experimentally demonstrated and analytically confirmed that viscous liquids can be effectively sensed by monitoring optomechanical vibration, which shows the feasibility of our sensor for bio-analyte sensing. We observed total mechanical resonance frequency shift of 1.35 MHz by varying the sucrose concentration of the solution inside the resonator (0 - 44 % (w/w)). Another usage of the microfluidic sensor is measurement of bio-activities near the sensor surface. Thus, we studied surface sensitivity of a microfluidic optomechanical resonator by layer-by-layer removal of SiO2 molecules from the inner surface of the resonator using hydrogen fluoride (HF). With 1.25 % (v/v) HF, mechanical resonance frequency shift of -240 kHz was observed over 24 minutes, with a surface sensitivity of 1.2 Hz/(pg/mm2) and a detection limit of 83 pg/mm2. We further observed the rate of mechanical frequency shifts to different concentrations of HF. In pressure sensitive optomechanical sensor study, we theoretically analyzed and experimentally demonstrated non-contact detection of air-coupled ultrasound using optical ring resonators. We observed detectable noise equivalent pressures of 6 mPa and 16.5 mPa for 50 kHz and 800 kHz in air, respectively. Furthermore, our ring resonators were able to detect air-coupled photoacoustic waves generated from a thin Chromium film. We observed that broadband photoacoustic wave was coupled into mechanical wineglass mode of the resonator with narrow bandwidth (~10 kHz). To improve the photoacoustic detection performance, we broadened the frequency response of the ring resonator to 200 kHz by encapsulating the ring resonator into D2O.

A cloud of ultracold atoms trapped within the confines of a high-finesse optical cavity shakes from the pressure of the light that probes it. This form of measurement backaction, a central component of quantum measurement theory, is the subject of this dissertation. Enlisting the collective motion of ultracold atoms as the mechanical degree of freedom in a cavity optomechanical system, we reach settings cold and quiet enough to allow for the effects of measurement backaction to manifest. We report predictions for and experimental observa- tions of the Standard Quantum Limit for force sensitivity, optical ponderomotive squeezing, and the possibility of complex squeezing through generalized optical correlations.

Abstract: Cavity optomechanical devices are interesting systems for probing quantum mechanical behaviour of mesoscopic objects. A basic requirement for these types of experiments is preparation of the mechanical resonator in, or at least very close to, its ground state. Although active laser cooling techniques can help this process, conventional cryogenic (pre-)cooling is nonetheless necessary. This thesis introduces a custom-made apparatus, housed on the base plate of a commercial dilution refrigerator, for coupling light into an optomechanical resonator via a tapered optical fiber. Our system incorporates full three-dimensional control of the taper-resonator coupling conditions, enabling critical coupling at cryogenic temperatures. It also features an optical microscope which permits in situ imaging and alignment of the taper and resonator, while causing minimal heating to the environment. Optomechanical measurements of silica bottle resonators, which exhibit optical whispering gallery modes and high-quality mechanical breathing modes, are performed using the dilution fridge system. Several methods for enhancing the detection of small mechanical signals are tested and a method for determining the temperature of the mechanical mode is described and implemented. The tight confinement of light circulating in the bottle resonator leads to increased optical absorption and significant heating of the silica, which manifests itself in both the optical and mechanical properties of the resonator. We present the first measurements of these resonators for mechanical mode temperatures as low as 4 K, and fridge temperatures down to 9 mK.

In the 70s, the interplay between microscale electronics and mechanics gave birth to micro- and nanoelectromechanical systems (MEMS/NEMS) that are prevalent in our daily life. The emergence of silicon photonics in the 90s was a result of the marriage between microelectronics and optics promising extreme communication bandwidth and processing power. A few years ago, the field of microscale optomechanics that harnesses the interaction between light and mechanics on a nanoscale emerged. The field witnessed the birth of many exciting technologies as quantum limited detection of ultra-weak forces, preparation of micromechanical oscillators close to their motional quantum ground states and enabling self-sustaining oscillations of mechanics with light. The aim of this thesis is to explore and address a few challenges in coupled optomechanical systems. So far, most work in this area focuses on single device behaviors. One could imagine that like connecting many transistors together leads to complex computing machines, a network of coupled optomechanical devices have the potential to offer dynamics that are not accessible with single optomechanical devices. In this thesis, I show that indeed, light can be used to synchronize arrays of mechanical oscillators even when they are not physically connected. I will also show in this thesis that coupling distinct optical and mechanical elements together could also enable a new paradigm of devices. We couple a single Carbon Nanotube (CNT) strongly to on-chip high-Q optical microcavi- ties. Despite the tiny size of CNT, we show that the optical microcavity is still extremely sensitive to the CNT motion. We demonstrate that we can observe in real-time the thermal Brownian motion of a single CNT for the first time. The unique carbon-optical system also enables an almost completely dissipative optomechanical system that has not been achieved in any other type of systems to date.

Abstract: Optomechanics, the sensing of mechanical movement using optical modes, has seen great advancement in recent years and has been used for its high displacement sensitivity to couple to a variety of mechanical devices. Torsional devices have historically been used for measuring de Haas-van Alphen effect, shear modulus, superfluids, superconductors, the angular momentum of light, switching of magnetic states, and other applications. Combining these two together, a silicon microdisk coupled to a torsional resonator has been observed before to have sensitivities of 4 nrad Hz−1/2 and 7 fm Hz−1/2. A cryogenic ultra-high vacuum (UHV) system holds the possibilities of analyzing these devices at 4 K in a much higher vacuum than has been studied before. We have retrofitted a former STM with a tapered optical fiber to couple light to a silicon microdisk. This “Photon STM” (P-STM) has the potential to not only couple to optical devices, but map the optical topography of a sample by using a modified tunnel current technique. This thesis shows how the P-STM was constructed and demonstrated its ability to couple to a 38 μm diameter optical disk and measured a nearby torsional resonator in high vacuum, with sensitivities down to 200 fm Hz−1/2 and 80 nrad Hz−1/2.

Light can generate forces on matter. The nature of these forces is electromagnetic force, or Lorentz force. The emergence and rapid progress of nanotechnology provided an unprecedented platform where the very feeble optical forces began to play significant roles. The interactions between light and matter in nanoscale has been the focus of almost a decade of active theoretical and experimental investigations, which are still ongoing and constitute a whole new burgeoning branch of nanotechnology, nano-optomechanical systems (NOMS). In such context, the general goal of my research is to generate, enhance and control optical forces on silicon photonics platforms, with a focus on developing new functionalities and demonstrating novel effects, which will potentially lead to a new class of silicon photonic devices for a broad spectrum of applications. In this dissertation, the concept of optical force and the general background of the NOMS research area are first introduced. The general goal of the silicon photonics research area and the research presented in this dissertation is then described. Subsequently, the fundamental theory for optical force is summarized. The different methods to calculate optical forces are enumerated and briefly reviewed. Integrated hybrid plasmonic waveguide (HPWG) devices have been successfully fabricated and the enhanced optical forces experimentally measured for the first time. All-optical amplification of RF signals has been successfully demonstrated. The optical force generated by one laser is used to mechanically change the optical path and hence the output power of another laser. In addition, completely optically tunable mechanical nonlinear behavior has been demonstrated for the first time and systematically studied. Optomechanical photon shuttling between photonic cavities has been demonstrated with a "photon see-saw" device. This photon see-saw is a novel multicavity optomechanical device which consists of two photonic crystal nanocavities, one on each side of it. Pumping photons into one cavity excites torsional optomechanical self-oscillation, which shuttles photons to the other empty cavity during every oscillation cycle in a well-regulated fashion. Last but not least, the effort made to develop reliable fabrication processes for NOMS devices is summarized.

Virtually every communications system today requires some form of reference oscillators. The need for miniaturized, batch manufacturable oscillators as chip scale timing references stems from the need to replace the well-established, high performing, albeit expensive quartz oscillators without compromising on performance. MEMS oscillators have recently found applications in various consumer electronic applications. With numerous advances in fabrication technology and materials processing, these oscillators are being pushed to create a presence in the high performance base-band market and high frequency applications. Scaling MEMS oscillators to high frequencies presents challenges in terms of reduced transduction efficiencies and material limits on quality factors. Opto-mechanical transduction offers higher sensitivity and opens up possibilities to interrogate high frequency mechanical resonances hitherto inaccessible. MEMS has also found a strong foothold in the several markets for inertial sensors. Typical MEMS accelerometers and gyroscopes operate at low frequencies (kHz) through electrostatic drive and sense. A limiting factor in the sensitivity of these sensors is the electronic noise in the sense circuitry. This thesis investigates how opto-mechanics can benefit the field of MEMS in low-phase noise oscillators and inertial sensors (gyroscopes). Using a previously demonstrated opto-acoustic oscillator (OAO), a driving scheme is presented for an OAO by simultaneously exploiting radiation-pressure (RP) and RF feedback oscillation mechanisms to achieve significantly lower phase noise than could be realized by either phenomenon solely. A theoretical model and experimental results are presented corroborating this scheme, demonstrating a silicon OAO operating at 175 MHz with a phase noise of -128.6 dBc/Hz at 1 MHz offset with 2.77 dBm RF output power, resulting in a 10dB far-from-carrier phase noise improvement. An opto-mechanical transduction scheme is then presented which is selective to sensing the wine glass modes in an on-chip integrated silicon mechanical resonator. By utilizing two orthogonal waveguides for opto-mechanical sensing at the anti-nodes of the desired wine glass mode, the phase difference between the wine glass modes can be used to selectively sense the desired wine glass modes as compared to other modes. The theoretical model for this transduction scheme is presented followed by the mechanical and optical design of several potential resonators. The design of the resonator, drive electrodes, and tunable waveguides are all explored. These designs are experimentally characterized for the 22.3 MHz and 25 MHz wineglass modes. Optical resonances were shown with loaded optical quality factors as high as 95k. Tunable optical coupling was shown with a DC bias gap-closing waveguide design that reduced the extinction of the optical resonance by 7dB with an applied voltage of -43.9V. Differential electrostatic drive was implemented and showed a 15dB suppression of the unwanted wineglass mode. The RF transmission of the wineglass modes for both waveguides showed out-of-phase signals for the wineglass mode of interest and in-phase signals for the other wineglass mode, consistent with what is needed for balanced differential detection. An application considered for these resonator designs and differential sensing scheme is as a vibratory gyroscope. The resonator designs are modified to reduce the wineglass mode splitting to 50-76kHz. Initial COMSOL simulations were performed by applying external rotations and measuring the displacements at the drive and sense from the resulting coriolis accelerations.

Abstract: Torsional oscillators are well known for their extensive applications ranging from measuring gravity to detecting angular momentum of light. When these torsional resonators scale down, through advanced nanofabrication techniques, the applications extend to measuring quantum effects such as the super fluidity in helium and Casimir forces. The benefits of torsional resonators will only increase with smaller structures, provided that they are supplied with a sensitive detection mechanism. The popular choice of interferometric scheme, for example, does not scale down well with nanoscale on-chip devices and requires a separate detection platform. Fortunately, there have been recent successes in on-chip cavity optomechanics where the mechanics can be sensitively measured through a high quality optical resonator. By increasing the coupling between the mechanical oscillator and the optical cavity, mechanical detection can be highly enhanced while the device is miniaturized. I have implemented, for the first time, an optomechanical platform using an optical microdisk evanescently coupled to torsional oscillators to demonstrate high torque sensitivities. The results have shown that optomechanics is highly desirable for nanoscale torsion devices opening doors for vast applications: we have achieved angular displacement sensitivity of 4 nrad per root-Hz, displacement sensitivity of 7 fm per root-Hz, and torque sensitivity of 0.8 zNm per root-Hz. To obtain high-quality silicon-on-insulator microdisks with gaps in the order of ~100 nm, we have chosen a commercial foundry to fabricate our sensitive devices which uses state-of-the-art photolithography procedures. The benefit of deep UV optical lithography is that many chips on a single 8-inch wafer are available that are cost-efficient over the electron beam lithography method. This thesis highlights the custom made optomechanical apparatus using a dimpled tapered fibre to sensitively probe commercially fabricated torsional devices, demonstrating the compatibility of optomechanics to nanoscale torsional platforms.

Nowadays, optical forces are widely used to control or measure the position of micrometer- to nanometer-sized particles, such as living cells, DNA and bacteria. Two major categories of optical forces are discussed here: gradient or dipole force and scattering force. The gradient force is originated from the fact that a polarizable micro-particle placed in a laterally varying optical field will experience different forces in the positively and negatively charged sides. In this thesis, we investigate the optical gradient force in 2D hybrid and plasmonic waveguides. Compared to the conventional dielectric waveguides, we show that the optical force can be enhanced by at least 1 order of magnitude in the hybrid and plasmonic waveguides. The scattering force is an axial force, which is the result of the momentum transfer from the radiating field to the dielectric medium. To investigate the radiation force, we mainly study two types of micro-resonators: wheel resonators and small disk resonators. To investigate the optical gradient force, we calculate the optical forces in two dimensional hybrid waveguides in which a dielectric waveguide is coupled with a metal substrate and plasmonic waveguides in which two identical metal waveguides are coupled. We compare coupled plasmonic waveguides with different geometries, including rectangular, circular, and triangular cross sections. In comparison with their corresponding dielectric structures, optical forces in both hybrid and plasmonic waveguides are greatly enhanced due to stronger evanescent waves and larger field gradients. To investigate the radiation force, we study three types of optomechanical oscillators: silicon nitride disk resonator, silicon nitride wheel resonator, and small silicon disk resonator. The experimental results show that the optomechanical coupling coefficiency increases from 0.8GHz/nm to 110GHz/nm, the effective mass decreases from 2ng to 6pg, the oscillation frequency increases from 10MHz to 1GHz, the device size shrinks from 60&\mu m to only 4&\mu m and the oscillation threshold improves from 500&\mu W to 8&\mu W. We also systematically investigate GHz optomechanical microdisk oscillators on the platform of SOI. We have tested small silicon disks with different radii. For the disks with the radii of 1.5&\mu m, 2&\mu m, 2.5&\mu m and 3&\mu m, fundamental breathing modes are detected. The mechanical Q is sensitively dependent on the undercut, since it plays an important role in the mechanical energy dissipation. The silicon disk with the radius of 2&\mu m and the undercut ratio of 90% oscillates at 1.27GHz under the dropped power below 10&\mu W. We also demonstrate the phenomena of the instability and RF mixing above optomechanical oscillation threshold. Then we study single, two side-coupled, and serially-coupled triple wheel resonator system. The single wheel resonator and two side-coupled wheel resonators have the same dimension with inner radius of 24.3&\mu m and outer radius of 34.3\mu m. In the single resonator, we observe that both the fundamental radial breathing mode and the flapping mode couple to a high Q optical mode and generate frequency mixing through the nonlinear optical transfer function. The harmonic generation of the flapping mode produces a comb-like frequency mixing spectrum. Instead of using the external pump modulation, we show that the regenerative oscillation of an internal mechanical mode can be used as a modulation source for optomechanical RF mixing. In the side-coupled resonators, the optomechanical transduction is related to the energy distribution in the two resonators, which is strongly dependent on the input detuning. Compared to a single resonator, the coupled resonators can still provide very sensitive optomechanical transduction even if the optical and mechanical quality factors of one resonator are degraded. The serially-coupled triple resonators have the dimension with inner radius of 20&\mu m and outer radius of 25&\mu m. A freestanding beam is placed in the vicinity of the middle resonator. In this coupled system, we demonstrate that the mechanical mode of the freestanding beam can be selectively coupled to different resonance supermodes through the near field interaction. All the devices are fabricated on the 300nm thick silicon nitride material with the silicon oxide as the sacrificial layer, and they are fully suspended with three thin spokes connecting to a center support. They have effective mass around 1ng and optomechancial coefficient in the level of 1GHz/nm.

Parametric devices have become a stepping stone in our development of modern technology and new scientific discoveries. They play a role in making astronomical observations with the use of parametric amplifiers as high-sensitivity low-noise first stage amplifiers, or in modern communications as amplifiers of optical frequency light. In addition, parametric devices have been successfully implemented in optomechanics to ''cool'' or ''heat'' mechanical motion. In fact, with such systems it has been possible to ``cool'' the motion of a mirror down to its quantum ground state, which is the lowest state of motion obtainable due to the quantum limit. The most common systems of the time consist of optical systems using optical cavities and fiber optics, or micro systems using planar superconducting strip resonators. In this dissertation parametric devices with cm-scaled RF cavities and oscillators are considered. The approach is to show that the same underlying effects that exist in optical systems also exist in with microwave cavities, and with the development of high-Q superconducting RF cavities feasible threshold for parametric effects are obtainable.

In this dissertation, I theoretically investigate the open system dynamics of cavity optomechanical systems in the quantum limit, where a mechanical resonator couples to a cavity mode via radiation pressure force. Recent developments in nano-fabrication and cooling techniques make it possible to optically control and manipulate the motion of micro- and nano-mechanical resonator. Several experiments have demonstrated the possibility of preparing macroscopic mechanical resonators into their quantum ground state, which makes optomechanical systems an ideal candidate for studying the quantum behavior of macroscopic objects. One important direction in quantum optomechanics is the study of the decoherence of optomechanical system due to the interaction with their external environments. This dissertation explores the decoherence effects by considering the influence of the radiation pressure coupling on the interaction between optomechanical system and its environments. Because the effects of the nonlinear interaction vary with the optomechanical coupling strength, three different interaction regimes are fully studied here: the weak coupling, the intermediate coupling and the strong coupling.

The coupling of macroscopic objects via the optical near-field can generate strong attractive and repulsive forces. Here, I explore the static and dynamic optomechanical interactions that take place in a geometry consisting of a silicon nanomembrane patterned with a square-lattice photonic crystal suspended above a silicon-on-insulator substrate. This geometry supports a hybridized optical mode formed by the coupling of eigenmodes of the membrane and the silicon substrate layer. This system is capable of generating nanometer-scale deflections at low optical powers for membrane-substrate gaps of less than 200 nm due to the presence of an optical cavity created by the photonic crystal that enhances both the optical force and a force that arises from photo-thermal-mechanical properties of the system. Feedback between Brownian motion of the membrane and the optical and photo-thermal forces lead to dynamic interactions that perturb the mechanical frequency and linewidth in a process known as ``back-action.'' The static and dynamic properties of this system are responsible for optical bistability, mechanical cooling and regenerative oscillations under different initial conditions. Furthermore, solid objects separated by a small distance experience the Casimir force, which results from quantum fluctuations of the electromagnetic field (i.e. virtual photons).The Casimir force supplies a strong nonlinear perturbation to membrane motion when the membrane-substrate separation is less than 150 nm. Taken together, the unique properties of this system makes it an intriguing candidate for transduction, accelerometry, and sensing applications.

This work explores the stochastic dynamics and important diagnostics of a mechanical resonator (nanobeam) used in cavity optomechanical sensors for atomic force microscopy. Atomic force microscopy (AFM) is a tool to image surface topology down to the level of individual atoms. Conventional AFM has been an essential tool for micro and nanoscale studies in physics, chemistry, and biology. Cavity optomechanical sensors for AFM extend the utility of conventional AFM into a new regime of high sensitivity k is approximately 1 N/m and high frequency f0 is approximately 10 MHz. Cavity optomechanical sensors for AFM are unique because they use near field optics to transduce the position of a nanobeam. The nanobeam is not able to be transduced by more conventional AFM techniques, such as laser interferometry, because the nanobeam is smaller than the spot size of the laser. This work determines the noise spectrum G of a nanobeam in water and in air. Also important diagnostics of the nanobeam are determined in air and in water. These important diagnostics include the quality factor Q and natural frequency in fluid omega_f. It is found that the nanobeam is overdamped in water. However, the nanobeam is underdamped in air and has quality factor of Q is approximately 4. The noise spectrum is determined from deterministic numerical calculations and the Fluctuation-Dissipation Theorem. This is possible because the same molecular processes, Brownian motion, cause both the fluctuations of the nanobeam and the dissipation of the nanobeam.

Atomically thin materials, which were discovered in 2004 with the isolation of graphene, represent a unique new building block for mechanical systems. Here, we explore the possibilities for a new class of mechanical devices based on these materials, with a focus on graphene-based resonant nanoelectromechanical systems. As a result of the recent progress in fabricating large-area graphene sheets, graphenebased mechanical devices have become vastly easier to manufacture and now show even greater promise for a range of applications, such as signal processing, sensing, and mechanical systems in the quantum regime. We discuss recent advances in fabrication and measurement techniques that make graphene resonators a viable technology, and present what is known about the performance of graphene mechanical systems. We demonstrate in the area of performance that room temperature graphene quality factor can be enhanced an order of magnitude by using a fully-clamped circular geometry with large diameter. We also show that the quality factor of a graphene resonator depends on its tension, and we suggest ways of enhancing the tension in graphene resonators. Finally, we simultaneously utilize graphene's electrical, mechanical, and optical properties in a novel application of graphene: photothermal graphene optomechanics. As a demonstration of the utility of this effect, we show that a continuous wave laser can be used to cool a graphene vibrational mode or to power a graphene-based tunable-frequency oscil- lator. By virtue of graphene's high thermal conductivity and optical absorption, photothermal optomechanics is efficient in graphene and could ultimately enable laser cooling of graphene mechanical systems to the quantum ground state or applications such as photonic signal processing.

Optical resonators are the basis of any experiment where it is desirable to confine light. The most basic optical resonator, a Fabry-Perot etalon, can be as simple as a colorful layer of oil over water, or as complicated as the parallel mirrors in the Laser Interferometer Gravitational-Wave Observatory. When looking for new phenomena, it is often useful to increase intensity. One example is optomechanics which was born after dissipation in resonators was reduced to a level where deformation caused by light pressure became significant. Intensity is related to the circulating power over the transverse area of the mode. Whispering gallery resonators can be ideal as they offer quality factors over 100 billion and can confine light to a transverse mode area smaller than a wavelength squared. While previous work in optomechanics relied on the force of light on the device walls, here we use the force of light on an acoustical density wave. We demonstrate a new family of optomechanics based on Brillouin scattering. Brillouin scattering is most widely known as a loss mechanism in telecom applications in which stimulated scattering limits the usable power. Here we show that stimulated Brillouin scattering of light from sound can be used as an optomechanical actuation mechanism for high frequency (11 GHz) acoustical vibrations. Owing to ultrahigh optical and mechanical quality factors, we are able to excite mechanical vibrations in Silica whispering gallery resonators at microWatt input powers and gained for the first time access to mechanical WGM in microresonators. While WGMs were first studied as mechanical phenomena in domed cathedrals, the term is currently used to describe optical modes despite the fact that light does not whisper. Here I enabled access to real (acoustical) whispering gallery modes in microresonators which further enabled us to transform Brillouin scattering into a cooling process. The combination of forward stimulated Brillouin scattering and backward stimulated Brillouin scattering allowed excitation of modes from 50 MHz to 11 GHz in frequency, and enabled for the first time reversing the energy transfer direction in the Brillouin process to allow cooling.