Superconducting radio frequency cavities have applications in fields including particle accelerators, force sensing, narrow filtering, and more. Here, we look at a progression of work with SRF cavities starting from the design and fabrication stage, then moving to frequency and quality factor measurements. A specific type of microwave cavity, the coaxial stub cavity, is considered. We look at the finite element simulations that calculate the TEM-like coaxial mode of the cavity and discuss the configuration of the electric and magnetic field components.

Once the prototypes are fabricated and tested, we turn to applications of this specific type of cavity. The high Q nature of this particular configuration allows for a highly selective filter element and is used in a hybrid optical-electrical device called the optoelectronic oscillator. We characterize the room temperature implementation of this device, which consists of a laser, a modulator, an optical delay line, a photodiode, an amplifier, and the cavity. This device produces an optical pulsetrain with a repetition rate determined by the filter element in the loop along with a high spectral purity, low phase noise microwave output whose frequency is also determined by the filter element. The phase noise, microwave, and optical spectra are characterized for room temperature and initial results from cryogenic experiments are shown for the microwave output.

Additionally, the coupling of a levitated magnet's mechanical oscillations to a radio frequency (RF) mode inside of a superconducting cavity may lay the groundwork for coupling to quantum objects whose states can be probed and controlled, such as magnons or transmons. We have previously reported levitation of a strong, mm-scale neodymium magnet within a cm-scale coaxial microwave resonator. In trying to better understand the behavior of the system, we have developed a finite element model that allows us to calculate the potential energy landscape of the cavity-magnet system. This can be done for a wide array of cavity and magnet specifications as well as any magnet orientation. By identifying the stable points, we can design the cavity such that levitation can be forced in regions of interest, such as regions of maximum electric and magnetic fields. We can also control the system's sensitivity to the magnet's motion and approximate the mechanical frequency at which the magnet vibrates about equilibrium. The calculated potential energy landscapes are used, in combination with other geometry-based FEM simulations, in comparison with experimental measurements of the shift in resonance frequency with the motion of the magnet when there is no optical access inside of the cavity at cryogenic temperatures.

The purpose of this dissertation work is to improve two applications of tunable light sources with fiber optical parametric oscillators based on microstructure optical fibers: CARS microscopy and single photon sources. Microscopy of live cells is a vigorous area of research and is mostly enabled by fluorescent labeling of molecules of interest. While fluorescence microscopy has facilitated a vast number of biological discoveries, there are drawbacks to adding labels to the live environment. Coherent Raman scattering spectroscopy techniques probe the low frequency nuclear vibrations of materials using high frequency fields in a label-free manner. Owing to the label-free chemical specificity of the technique, the development of a lightweight, easy-to-use light source for coherent Raman scattering spectroscopy has a suite of implications for advancing biophotonics, clinical photonics, atmospherics and space exploration. CRS techniques require dexterous wavelength tuning in order to probe the wide variety of vibrational modes relevant to cell biology. We explore the benefits of fiber optical parametric oscillators as tunable light sources for CARS microscopy, namely the output power through polarization management and intensity noise characteristics. On the other side of the power scale, we explore the potential application of fiber parametric devices to improving single photon light sources. Fiber based platforms, which utilize spontaneous four-wave mixing (SFWM), present a potential simplification in the generation of correlated photon pairs over their solid-state counterparts that are based on spontaneous parametric down conversion (SPDC). This is primarily because SPDC sources require extensive filtering to perform efficient heralding. Fiber based systems can provide a dexterous tuning of entanglement properties for quantum information applications. We propose a characterization study of correlations between various output regimes in a fiber-based correlated photon pair source.

Multicore microstructure fibers have emerged as promising components in ultrahigh capacity transmissions, biomedical imaging, quantum computing and signal-processing applications like wavelength conversion, and optical amplification. For long-haul transmission they are attractive due to low differential group delay and nonlinear impairment reduction depending on the number of cores. In this thesis we explore the linear-optical and nonlinear-optical properties of single and triple-core microstructure fibers with the goal of using them in parametric devices based on the four-wave mixing (FWM) nonlinearity Although the presence of multiple cores in a fiber produces drawbacks as well as advantages, we experimentally demonstrate that FWM and parametric oscillation are possible in multicore microstructure fibers. One such advantage is the ability to increase the power conversion efficiency of a fiber optical parametric oscillator (FOPO). We also present results for a FOPO built using a single-core microstructure fiber and demonstrate a higher power extraction using a polarization-based output coupling method compared with a polarization-independent method.

We discuss measurements of the group velocity dispersion over a wavelength range from 1064-1600 nm. We study the mode coupling among the cores as a function of input power, polarization, wavelength, and spectral broadening. We demonstrate FWM in a triple core microstructure fiber at 1064 nm and study the transition between the case where FWM happens primarily in a single core and the case where FWM is distributed among multiple cores. We find that the effective nonlinear coefficient is reduced by a factor of 3 (the number of cores) when the coupling length is short compared with the nonlinear length, and that this leads to a three-fold reduction in the FWM bandwidth.

Coherent Raman Scattering (CRS) microscopy is a technique used to image cells through the use of intrinsic chemical bonds, which allows for label free imaging at video rate speeds. Since the process is coherent the generated signal is orders of magnitude higher than spontaneous Raman microscopy. Many light sources have been developed for CRS microscopy, such as solid state optical parametric oscillators, supercontinuum sources, and fiber lasers. Fiber optical parametric oscillators (FOPOs) are tunable light sources based on the χ⁽³⁾ nonlinearity found in SiO₂. They have the potential to be integrated into compact and robust fiber components. This thesis describes an optimization for output power through tailoring the polarization at the output coupler and characterizes two FOPO systems for their applications in CRS microscopy. Chapter 1 gives a conceptual overview of spontaneous Raman, coherent anti-Stokes Raman scattering (CARS), stimulated Raman scattering (SRS) techniques as well as the pump sources typically used to perform CRS microscopy. Chapter 2 summarizes the physics for understanding FOPO operation. Chapter 3 describes our results for optimizing output power for a Nd:YVO₄ pumped FOPO by using a polarizing beam splitter with polarization dependent components. Chapter 4 illustrates a Ti:Sapphire pumped FOPO and compares its performance with the Nd:YVO₄ system.

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.

Active matter is a growing interdisciplinary field of science that studies the collective motion of different species of particles and living organisms. This field of research is often bio-inspired as collective motion of fish, birds and insects are ubiquitous throughout nature. Such behavior is not just limited to the macroscopic world but is also found in the micro- and nanoscopic realms as well. Under the microscope, it can be observed that bacterial and protein assemblies are subject to the same group motion serving as the inner machines vital to the functions of life and natural forces of the world. In this thesis, I focus attention to the interesting method of an actively driven bundled microtubule network in a lyotropic liquid crystal phase.

The active nematic bundled microtubule system has gained substantial international exposure in the field of soft matter. Several groups across the world have not only reproduced this novel system, but also developed new methods to measure and probe its properties and kinematics. These actively driven protein networks have become a useful framework to study energy driven particles in complex structured fluids. An interesting method to probe the behavior of this system is the the implementation of boundaries serving as a useful strategy to control defect flow, morphology and dynamics. In this thesis, I study the behavior of an active nematic microtubule system confined to several different geometries. I was initially motivated from our preliminary work, when I observed that submerged 3D structures can influence defect dynamics by organizing their flows and pinning defects at specific locations. This prompted me to investigate active nematic flows in microfluidic devices in different confining conditions, which will be covered in this work.

For my first project, I engineered micropatterned surfaces using photolithography to control local orientation directors to take advantage of the interplay between surface curvatures and topological defects. Epoxy-based lithography represents a simple approach to develop lab-on-a-chip methods to probe active materials. In this dissertation, I will discuss optimized fabrication methods using negative tone epoxy-based photoresists to create microfluidic devices for active matter systems. I demonstrate that arrays of circular structures and submerged topographies can generate a variety of liquid crystal defect configurations, not typically observed on unconfined planar surfaces. I then build on these observations by considering the creation of new interfaces not limited to hard boundaries.

For my second project, I demonstrated that soft or virtual boundaries can be generated by submerged structures. With the assistance of micro patterned surfaces, different submersed geometrical patterns were created for my analysis: trenches, pillars, stairways, and undulated sinusoidal structures. I investigated the spontaneous flows of this novel system as pillar dimensions influenced active material flow due to abrupt changes in oil depth. This created virtual boundaries because of the change in the effective viscosity in proximity to the boundary. In this study, I collaborated with several groups to develop simulations and other micro-milled patterns.

Finally, my third project was to confine active material but by curving the oil-active layer interface, creating a two-tiered elevated system. The geometry for this work was submersed pillars impinging on the interface, creating a two-tier continuous active layer in which material is partially confined. Active flows above the pillars were influenced by the circular geometry and the thin oil layer resulting in physical changes of the material i.e., depletion. Building from the second project, the thin oil layer beneath the active material was thinner in the region above the pillars relative to outside the encircled area, consequently producing an area of higher effective friction. This was confirm using 3D reconstructions of the curvature of the active layer and auto-fluorescent pillar using confocal microscopy. This resulted in changes of velocity fields, defect densities and active length scales.

Overall, I have investigated new methods for probing a living liquid crystal system capable of generating internal flows using microfluidic devices. This new way to confine active material opens many opportunities to control and organize topological defects and materials at nanoscales using simple micro-fabricated structures. I hope that we can move this method and platform to other active or even passive liquid crystal systems for biomedical and electronic devices. Such methods can be invaluable to pursue the integration of liquid crystal phase to nanoelectronics. The work presented in this dissertation has demonstrated the adaptability of this active protein assembly and open new possibilities to organize structured fluids.

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.

Dual-beam fiber trapping is a versatile technique for manipulating micron-sized particles, biological assemblies, and living cells. Here, we fabricate fiber-based trapping platforms from plexiglass chips of polycarbonate and cast acrylic. Single-mode fibers from 980 nm fiber-pigtailed laser diodes are arranged in a counter-propagating configuration and situated into alignment. Fiber alignment is verified via coupling efficiency experiments whereby measured efficiency profiles assure proper alignment for trapping.

The initial stages of this project involved fabrication and testing of these trapping platforms. We calibrate the range of forces exerted on trapped polystyrene microspheres in water by suddenly offsetting one of the laser power outputs. The sudden offset causes a trapped microsphere to undergo a small displacement from the trap center. The displaced particle as a function of time follows a characteristic curve of over-damped harmonic motion. We then extrapolate the related spring constants which is proportional to the scattering force acting along the beam axis. Measured spring constants are in the range of 104-145 nN/m which are in agreement with expected values.

Subsequently, we demonstrate for the first time, stable trapping and stretching of low contrast giant lipid vesicles in solution. Trapped vesicles encapsulate poly(ethylene) glycol solution and are trapped with femtonewton range forces. We analyze the lipid membrane response to a range of optical stresses that initiate membrane stretching. At increasingly higher powers, we observe elongation of a vesicle along the beam axis (vesicle major axis) and contraction in the transverse direction (vesicle minor axis). The peak stress exerted along the beam axis is calculated for each incident power. Lipid vesicles stretch in a linear fashion for relative deformations up to 25%, correlating to applied peak stresses ranging from 7-60 mN/m2. Nonlinear deformations are observed at even higher applied optical stress. These experiments demonstrate the capabilities for trapping a variety of low-contrast, soft biomaterials.

This dissertation consists of three distinct projects: optical trapping, parametrically-driven oscillator, and physics education research. We trapped trap poly(methyl methacrylate) (PMMA) microspheres using radiation pressure forces when the refractive index ratio between the particles and the liquid medium suspending them was nearly one. This contrast resulted in a unique trapping landscape which was verified through our simulations. In the case of our parametrically oscillating pendulum, we modulated a parameter of the system, in this case the length of the pendulum, which gave rise to an instability which gradually increased the total energy of the oscillating pendulum. This system is an upper-level undergraduate laboratory experiment, where students would explore mechanical parametric oscillations and extract key linear pendulum features, such as the damping constant and the quality factor, and nonlinear dynamical features, such as frequency shifts and bistability. In the physics education research, I tested whether students would improve their ability to understand the material in the first semester of general physics (the majority of which are related to forces) if they were constantly required to develop robust solutions with low-stakes assignments. The results presented show that a positive correlation existed between implementing class presentations where students are required to solve problems robustly in groups and with both low and high stakes assignments.