Engineering

Permanent URI for this collectionhttps://digital.lib.washington.edu/handle/1773/19653

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Magneto-Optical Trapping and Control for a Neutral Atom Quantum Computer
(2026-02-05) Hu, Buke; Parsons, Maxwell MP
This thesis presents the design, implementation, and characterization of a Rubidium-87Magneto-Optical Trap (MOT) developed as a part of the foundation of a neutral atom quantum computing platform. A two-dimensional (2D) MOT and a 2D+ MOT configuration are realized to generate and deliver a cold atomic beam for future three-dimensional trapping. The experimental system integrates laser locking based on saturated absorption spectroscopy, radio-frequency control of acousto-optic and electro-optic modulators, permanentmagnet field generation, and a real-time FPGA-based control system. The 2D MOT is characterized using fluorescence imaging, and the 2D+ atomic beam is characterized by transversal probe beam spectroscopy. We extract the linewidth and assess Doppler and power-broadening effects. The results demonstrate stable generation of a collimated atomic beam and establish a robust testbed for future integration with optical tweezers and scalable neutral atom quantum computing architectures.
Design and Evaluation of Three Dimensional (3D) Current Collectors for Lithium Metal Batteries: Insights from Meta-Analysis and Experimental Studies
(2025-10-02) White, Julia; Yang, Jihui
As energy demand for mobile applications grows exponentially worldwide, energy storage solutions are becoming increasingly important. Electrochemical storage in the form of batteries is already widespread, but design demands for new applications require novel solutions. Lithium metal batteries (LMBs) are regarded as a promising avenue for significantly boosting the gravimetric energy density of batteries, a property that is particularly important for electric vehicles. However, the instability of the lithium metal anode (LMA) continues to hinder performance. Three-dimensional (3D) current collectors (electrically conductive substrates) have frequently been proposed as a solution, but many questions remain regarding which properties are most critical for performance and how the structures behave in realistic configurations. This thesis addresses these questions to guide the design and implementation of 3D current collectors in high-energy-density LMBs. A vast body of literature already exists surrounding 3D current collectors for LMA. However, few efforts have systematically analyzed the relationships between structural parameters of the current collector and anode performance to inform design. A coupled meta-analysis of published results and machine learning (ML) and data science techniques was undertaken to extract trends between 3D current collector structure and composition and cell performance metrics of Coulombic efficiency (CE) and cycle life (number of charge-discharge cycles before failure). The analysis revealed no correlation between structural pore diameter and performance but showed that a low to moderate specific surface area correlates to higher CE and cycle life than high specific surfaces areas. The analysis also indicated that the presence of oxygen and tin on base structures improves performance. These findings were validated experimentally: a low specific surface area carbon current collector outperformed a high surface area counterpart, and 3D copper structures incorporating oxygen and tin outperformed unmodified structures. The study highlights the value of meta-analysis for uncovering cross-cutting insights across diverse studies. Beyond the lack of clarity on optimal structural properties, few studies have examined the effects of combining 3D current collectors with various electrolytes (ionic conductor between electrodes) or have incorporated a lithium reservoir. Four commercially available copper current collectors were paired with four different electrolytes to assess how these factors influence cycling performance with a 4 mAh/cm2 lithium reservoir. Coulombic efficiency (CE) measurements revealed no statistically significant difference in CE across different current collectors within the same electrolyte. However, significant variation was observed when the electrolyte was changed while using the same current collector. Although polarization, electrochemical impedance, and lithium morphology varied between structures and electrolytes, no consistent patterns emerged to identify a clearly superior current collector structure. These results suggest that when a lithium reservoir is used, the choice of current collector structure becomes less critical, and efforts should instead prioritize electrolyte selection and design.
Highly Tunable Integrated Self-Interference Cancellation Techniques for Intelligent Full-duplex Radios
(2025-08-01) Li, Xichen; Rudell, Jacques
The growing demand for wireless connectivity in both defense and commercial applications, such as autonomous vehicles, smart cities, industrial IoT, and augmented reality (AR) / virtual reality (VR), continues to drive research towards increasing date rates in mobile transceivers while simultaneously reducing power consumption, form factor, and costs.With the advent of fifth generation (5G) and the ongoing development of sixth generation (6G) technologies, the increased utilization of the limited wireless spectrum, particularly in the S and C bands, for higher bandwidth and data rates has posed significant interference challenges among transceivers. In-band Full-duplex (FD) communication offers a solution by increasing spectral efficiency by enabling a radio's transmitter and receiver to operate simultaneously on the same channel frequency. This capability is particularly valuable for 5G/6G applications that require high data rates in congested wireless networks. However, a major challenge in FD systems is self-interference (SI), where the radio's transmitter signal interferes with its own receiver, degrading the radio's performance. This dissertation explores and implements integrated FD radio front-end solutions designed to mitigate SI and enhance data rates. The research focuses on developing SI cancellation techniques with high tunability, broad cancellation bandwidth, deep cancellation depth, and fast configuration speed. These innovations aim to enable practical radio hardware solutions for true FD operation, addressing the challenges of wireless network congestion in 5G/6G communications. This dissertation begins with a theoretical analysis of the design considerations for a feedfordward canceler for broadband SI cancellation, supported by circuit simulation and measurement results. A testbed including an integrated electrical balanced duplexer (EBD) coupled with a finite impulse response (FIR) filter-based feedforward canceler is used to evaluate the efficacy of the proposed design guidelines. Next, a linearity model is developed to examine the generation of nonlinearties from common- and differential-mode SI at the input of FD radio receivers, providing a strategy to minimize SI-induced distortion from nonlinear receiver impedance. These design considerations are then applied to the implementation of two FD transceiver front-end integrated circuits (ICs) featuring SI cancellation capabilities. The first IC is a FD transceiver front-end designed to achieve broadband SI suppression, with cancelers calibrated for enhanced linearity and the ability to cancel long-delay spread SI. Fabricated in a TSMC 40 nm CMOS process, this chip integrates an EBD with a tuned impedance matching network (Z\textsubscript{Bal}), two broadband complex 5-tap continuous-time FIR-based RF cancellation filters, and a mixed-signal baseband cancellation path operating with a Xilinx RFSoC to address long-delay spread ($\tau$$=$+174 \textit{n}s) SI. This design achieves a measured SI suppression of 62 dB across a +120 MHz bandwidth for delay spreads between 0-0.28 \textit{n}s, and SI cancellation of 23 dB across +120 MHz bandwidth for delay spreads between 0.4-174 \textit{n}s. The RF canceler, calibrated using digitally-controlled current DACs, demonstrates a maximum input-referred third-order intercept point (IIP\textsubscript{3}) of +42 dBm. The receiver has a measured noise figure of 6.8 dB and an IIP\textsubscript{3} of -21 dBm at the maximum gain setting of 40 dB. Additionally, an integrated harmonic-rejection power amplifier (PA) achieves a measured maximum output power (\textit{P\textsubscript{Sat}}) of 19.1 dBm and power-added efficiency (PAE) of 27\%. The second IC demonstrates a highly tunable SI canceler augmented with a machine-learning-based adaptation loop for deep cancellation, enhanced linearity, and accelerated convergence time. This prototype 2.4 GHz canceler chip, fabricated in a 40 nm CMOS process, features extensive tuning capabilities in filter coefficients, delay spread, and linearity. It operates in concert with a neural network (NN) algorithm implemented on a Xilinx RFSoC evaluation kit to optimize the canceler's adaptation process. Designed as a discrete add-on, this canceler IC can be integrated with transceiver chips from different manufacturers. The chip, implemented as a 6-complex tap finite impulse response filter, achieves a measured maximum SI cancellation of 32 dB over a 40 MHz bandwidth and an IIP\textsubscript{3} of +38 dBm. The proposed NN computes the initial settings for the canceler, followed by a local optimization process, achieving a convergence time of about 10 miliseconds in real-world wireless environments. The combined techniques proposed in this dissertation, focusing on enhancing tunability of SI cancellation, demonstrate a potential to achieve deeper cancellation depth, broader cancellation bandwidth, higher canceler linearity, and faster adaptation convergence for FD radios. These advancements enable new opportunities to increase wireless network capacity, addressing the growing demands of future 6G applications.
Resistive Switching Effects of Vanadium Pentoxide Thin Film
(2018-04-24) Wan, Zhenni; Anantram, Manjeri; Darling, Robert B
In this Ph.D. work, the resistive switching effects of vanadium pentoxide (V2O5) thin films are extensively explored and investigated. Contrary to conventional Flash memory devices where the information is stored by the electrons in the floating gate (FG), emerging memory devices employs the resistive switching effects of metal-insulator-metal (MIM) devices in which the information is stored in the location of atoms, which determines the high or low resistance state. Both reversible and irreversible resistive switching are discovered for the first time in V2O5 based MIM devices and the switching effects are studied as a function of metal contacts and environment, which play an important role in determining the device characteristics. Two conductor materials, chromium and indium tin oxide (ITO), are mainly investigated and the mechanisms for both irreversible and reversible switching are addressed. The dependence of switching effects on testing environment is enabled by building a vacuum test chamber. The devices are tested in a variety of gases environment and the role of intercalated H2O molecules in enabling the resistive switching is established. Resistance change is attributed to reduction of valence states of vanadium at electrode/V2O5 interface resulting from the electrochemical reactions when a voltage bias is applied. Reversibility of the switching is determined by whether the electrode material has the capability of temporarily storing oxygen ions. V2O5 xerogel film synthesized by sol-gel process experiences drastic atomic structural change during post annealing process, resulting in significant impact on resistive switching characteristics. X-ray diffraction analysis reveals that -phase V2O5 forms at bottom V2O5/ITO interface while -phase V2O5 forms at top V2O5/ITO interface. The presence of intercalated H2O molecules is essential for the reversible switching to occur. Ab initio calculations prove that the enlarged interlayer spacing in V2O5 xerogel significantly reduces the formation energies of oxygen vacancies, thus enabling the creation of mobile oxygen ions. In order to make the synthesis of V¬2O5 thin film more compatible with modern IC fabrication processes, thermal evaporation is employed for V2O5 deposition. Reversible bipolar switching is preserved and the stability of I-V characteristics over annealing temperature has been improved. DFT calculations are performed to simulate the amorphous V2O5 structure generated by melt-quench process using ab initio molecular dynamics technique. Formation energies of oxygen vacancy is also reduced in amorphous V2O5. Degradation of V2O5 film due to spontaneous reduction of vanadium oxide with presence of intercalated water molecules has been suppressed.
Real-Time Prediction of Lean Blowout using Chemical Reactor Network
(2018-04-24) Kaluri, Abhishek; Novosselov, Igor V
The lean blow-out (LBO) of gas turbine combustors is a concern that can limit the rate of descent for an aircraft, the maneuverability of military jets, and cause a costly and time-intensive reignition of land-based gas turbines. This work explores the feasibility of a model-based combustor monitoring for the real-time prediction of combustion system proximity to LBO. The approach makes use of (1) real-time temperature measurements in the reactor, coupled with (2) the use of a real-time chemical reactor network (CRN) model to interpret the data as it is collected. The approach is tested using a laboratory jet-stirred reactor (JSR), operating on methane at near atmospheric pressure. The CRN represents the reactor as three perfectly stirred reactors (PSRs) in series with a recirculation pathway, the model inputs include real-time reactor temperature measurements and mass flows of fuel and air. The goal of the CRN is to provide a computationally fast means of interpreting measurements in real time with regard to blowout proximity. The free radical concentrations and their trends and ratios are studied in each reactor zone. The results indicate that the hydroxyl radical maximum concentration moves downstream as the reactor approaches LBO. The ratio of hydroxyl radical concentrations in the jet region versus the recirculation region is proposed as a criterion for the LBO proximity. This real-time, model-based monitoring methodology sheds insight into combustion processes in aerodynamically stabilized combustors as they approach LBO.
High Accuracy Mobile 3D Scanning Using Structured Laser Beam Patterning
(2017-02-14) Makhsous, Sepehr; Mamishev, Alexander V
A person's diet affects their weight, lifespan, and chances of occurrence of such medical problems as diabetes, obesity, and cancer, to name a few. Enhanced dietary assessment techniques are critical for epidemiological studies that target diet-related problems. Currently, nutritional research is considerably hindered by the low accuracy in estimating individual dietary intake, and, more specifically, portion size. Dietary assessment plays an increasingly significant role in modern medical research. While inadequate diets can increase the risk of diabetes, obesity, and cancer. It is essential to design accurate, cost-effective tools that measure dietary data to advance nutritional research. This dissertation describes a low-cost and efficient method of calculating nutritional information by using 3D reconstruction and image processing. This system is called Dietary Data Recorder System (DDRS), which consists of a smartphone, a laser projector, and the main algorithm, which extracts the data from the DDRS for volume and nutritional calculations. The DDRS software consists of four main algorithms: Automatic Laser Detection algorithm, Segmentation algorithm, 3D Mapping algorithm, and Nutritional Estimation algorithm. In particular, this dissertation focuses on the first two functions: Automatic Laser Detection algorithm and Segmentation algorithm.

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