Scalable Nanophotonic Light Management Design for Solar Cells

The current trend in wide adoption of solar energy is encouraging in the context of current projections of increasing energy consumption and the dire need to decrease carbon emissions. The solar industry has expanded due to scientific advances in the power conversion efficiency of solar modules. In order maintain a rapid pace of adoption and further decrease electricity costs, converting each photon becomes increasingly important. This work focuses on nanophotonic approaches to increasing the power conversion efficiency of different solar photovoltaic designs. The projects voluntarily impose certain design constraints in order to be compatible with the large scale manufacturing needed by the solar industry. A focus was given to designs that can leverage the promising technology of nanoimprint lithography. Amorphous silicon tandem cells with embedded nanophotonic patterning attempted to increase absorption while minimizing materials and time costs. Simulated designs of Copper Indium Gallium Diselenide absorbers showed that the management of excited carriers is equally as important as light management in decreasingly thin absorber layers. Near perfect anti-reflection structures were given a detailed physical analysis to better describe the fundamental physics of near zero reflection due to nanocones printed on solar cell encapsulation glass. Experimental results agreed with the theoretical analysis, and showed that these nanostructures further increased absorbed photocurrent by trapping light in the encapsulation glass. Finally, a unique device in the form of a tandem luminescent solar concentrator/silicon solar module was proposed and analyzed as a low cost and adaptable technology for increased solar power conversion efficiency. Key to this design was discovery of new, near-perfect components for light management. Exciting and innovative designs are proposed to control the light-matter interaction within these devices. Study of a photonic luminescent solar concentrator predicted that luminescence can be trapped in photonic crystal slab waveguides with near zero loss. Rigorous experimental efforts to characterize a multitude of near-perfect samples help guide these designs toward their final goals

Cross-Layer Design of Highly Scalable and Energy-Efficient AI Accelerator Systems Using Photonic Integrated Circuits

Artificial Intelligence (AI) has experienced remarkable success in recent years, solving complex computational problems across various domains, including computer vision, natural language processing, and pattern recognition. Much of this success can be attributed to the advancements in deep learning algorithms and models, particularly Artificial Neural Networks (ANNs). In recent times, deep ANNs have achieved unprecedented levels of accuracy, surpassing human capabilities in some cases. However, these deep ANN models come at a significant computational cost, with billions to trillions of parameters. Recent trends indicate that the number of parameters per ANN model will continue to grow exponentially in the foreseeable future. To meet the escalating computational demands of ANN models, the hardware accelerators used for processing ANNs must offer lower latency and higher energy efficiency. Unfortunately, traditional electronic implementations of ANN hardware accelerators, including CPUs, Graphics Processing Units (GPUs), Application-Specific Integrated Circuits (ASICs), and Field Programmable Gate Arrays (FPGAs), have fallen short of meeting the latency and energy efficiency requirements for processing deep ANN models. Furthermore, the interconnection network subsystems in these electronic accelerator systems, designed to facilitate large-scale data transfers between processing cores and memory/control units within the accelerator systems, have become bottlenecks that hinder the throughput, latency, and energy efficiency of deep ANN model processing. Fortunately, Photonic Integrated Circuits (PICs)-based accelerator systems, featuring photonic network subsystems are promising alternatives to conventional electronic accelerators. PIC-based accelerator systems operate in the optical domain, delivering processing at the speed of light with ultra-low latency, minimal dynamic energy consumption, and high throughput. These advantages stem from the wavelength division multiplexing capabilities and the absence of distance-dependent impedance in PICs. Furthermore, these characteristics enable the implementation of high-performance photonic network subsystems within PIC-based accelerator systems. Additionally, PIC-based accelerator systems offer inherent optical nonlinearities. Despite these numerous advantages over electronic accelerators, PIC-based systems still encounter several challenges due to limited optical power budget, susceptibility to crosstalk and other sources of noise caused by the analog operation, high area consumption, and restricted functional flexibility of PICs. These challenges manifest in various ways. (i) The existence of a significant trade-off between the achievable processing core size and the supported bit precision that impedes the scalability of processing cores. (ii) The limited reconfigurability, in terms of supported computing size and precision, makes them less adaptable to modern ANN models with diverse computational and precision demands. (iii) The reliance on electronic adder networks for accumulation diminishes the latency and energy consumption benefits of PIC-based accelerator systems due to frequent analog-to-digital conversions and memory accesses involved in accumulations. My research has contributed several solutions that overcome a multitude of these challenges and improve the throughput, energy efficiency, and flexibility of PIC-based AI accelerator systems. I identified and analyzed factors that affect the scalability and reconfigurability of PIC-based AI accelerator systems. I proposed several novel PIC-based accelerator architectures with enhancements at the circuit level, architecture level, and system level to improve scalability, reconfigurability, and functional flexibility. At the circuit level, these enhancements serve to decrease optical signal losses, reduce control complexity, enable adaptability for various ANN processing tasks, and lower power and area consumption. The architecture-level improvements mitigate crosstalk noise, facilitate functional reconfigurability, enable in-situ and flexible spatio-temporal accumulation, and provide flexible support for different dataflows. The system-level enhancements involve the integration of stochastic computing with PIC-based accelerators to break the inherent trade-off between scalability and supported bit precision. Additionally, applying stochastic computing enhances the flexibility of PIC-based accelerators, allowing them to support mixed-precision ANN models. These cross-layer enhancements collectively contribute to the design of PIC-based AI accelerator systems, resulting in improved throughput, energy efficiency, scalability, and reconfigurability

Ferramenta de apoio para a aplicação de nanoengenharia no desenvolvimento de processos de fabrico eco-eficientes

The aim of this work is to present the NanoTechnology Usability (NTU) index tool, created and developed in order to reduce the gap between nanotechnologybased products developed in R & D centers and their effective application and utilization, promoting the optimized selection of materials and the use of ecoefficient production techniques. In this sense, the doctoral work contextualizes the current market of the types of commercially available nanomaterials, the most used synthesis methods, their current and potential market applications, current standards, obstacles and uncertainties with regard to the production, manipulation and assembling of nano-based products. Existing models and tools currently in the market, particularly that address ecodesign and nanotechnology, are also presented. Based on the diversity of the nano-based product, specific application, maturity level, type of nanomaterials used and synthesis methods, the NTU is applied to four case studies for further discussion and analysis of the results.O presente trabalho propõe-se a apresentar a ferramenta índice de utilização de nanotecnologia (NTU) criada e desenvolvida com o intuito de diminuir o hiato existente entre os produtos baseados em nanotecnologia desenvolvidos nos centros de I&D e a sua aplicação e utilização efetiva, promovendo a seleção otimizada dos materiais e a utilização de técnicas de produção eco-eficientes. Desta forma, o trabalho de doutoramento contextualiza o mercado atual dos tipos de nanomateriais disponíveis comercialmente, os métodos de síntese mais utilizados, as suas aplicações atuais e potenciais no mercado, as normas vigentes, os obstáculos e incertezas no que diz respeito à produção, manipulação e assemblagem de produtos baseados em nanotecnologia. Os modelos e ferramentas existentes atualmente, em particular, que endereçam o ecodesign e nanotecnologia são também apresentados. Baseado na diversidade no que concerne o tipo de produto baseado em nanotecnologia, aplicação específica, nível de maturidade, nanomateriais usados e método de síntese, o NTU é aplicado a quatro casos de estudo para sua discussão e análise de resultados.Programa Doutoral em Engenharia Mecânic

Towards many-body physics with Rydberg-dressed cavity polaritons

An exciting frontier in quantum information science is the creation and manipulation of bottom-up quantum systems that are built and controlled one by one. For the past 30 years, we have witnessed signi cant progresses in harnessing strong atom- eld interactions for critical applications in quantum computation, communication, simulation, and metrology. By extension, we can envisage a quantum network consisting of material nodes coupled together with in nite-dimensional bosonic quantum channels. In this context, there has been active research worldwide to achieve quantum optical circuits, for which single atoms are wired by freely-propagating single photons through the circuit elements. For all these systems, the system-size expansion with atoms and photons results in a fundamental pathologic scaling that linearizes the very atom- eld interaction, and signi cantly limits the degree of non-classicality and entanglement in analog atom- eld quantum systems for atom number N 1. The long-term motivation of this MSc thesis is (i) to discover new physical mechanisms that extend the inherent scaling behavior of atom- eld interactions and (ii) to develop quantum optics toolkits that design dynamical gauge structures for the realization of lattice-gauge-theoretic quantum network and the synthesis of novel quantum optically gauged materials. The basic premise is to achieve the strong coupling regime for a quantum many-body material system interacting with the quantized elds of an optical cavity. Our laboratory e ort can be described as the march towards \many-body QED," where optical elds acquire some properties of the material interactions that constrain their dynamical processes, as with quantum eld theories. While such an e ort currently do not exist elsewhere, we are convicted that our work will become an essential endeavor to enable cavity quantum electrodynamics (QED) in the bona- de regime of quantum many-body physics in this entanglement frontier. In this context, I describe an example in Chapter 2 that utilizes strong RydbergRydberg interactions to design dynamical gauge structures for the quantum square ice models. Quantum uctuations driven by cavity-mediated in nite-range interaction stabilize the quantum-gauged system into a long-range entangled quantum spin liquid that may be detected through the time-ordered photoelectric statistics for photons leaking out of the cavity. Fractionalized \spinon" and \vison" excitations can be manipulated for topological quantum computation, and the emergent photons of arti cial QED in our lattice gauge theoretic system can be directly measured and studied. The laboratory challenge towards strongly coupled cavity Rydberg polaritons encompasses three daunting research milestones that push the technological boundaries beyond of the state-of-the-arts. In Chapter 3, I discuss our extreme-high-vacuum chamber (XHV) cluster system that allows the world's lowest operating vacuum environment P ' 10 Torr for an ultracold AMO experiment with long background-limited trap lifetimes. In Chapter 4, I discuss our ultrastable laser systems stabilized to the ultra-low-expansion optical cavities. Coupled with a scalable eld-programmable-gate-array (FPGA) digitalanalog control system, we can manipulate arbitrarily the phase-amplitude relationship of several dozens of laser elds across 300 nm to 1550 nm at mHz precision. In Chapter 5, we discuss the quantum trajectory simulations for manipulating the external degrees of freedom of ultracold atoms with external laser elds. Electrically tunable liquid crystal lens creates a dynamically tunable optical trap to move the ultracold atomic gases over long distance within the ultra-high-vacuum (UHV) chamber system. In Chapter 6, I discuss our collaborative development of two science cavity platforms { the \Rydberg" quantum dot and the many-body QED platforms. An important development was the research into new high-index IBS materials, where we have utilized our low-loss optical mirrors for extending the world's highest cavity nesse F 500k! We discuss the unique challenges of implementing optical cavity QED for Rydberg atoms, which required tremendous degrees of electromagnetic shielding and eld control. Single-crystal Sapphire structure, along with Angstrom-level diamond-turned Ti blade electrodes, is utilized for the eld compensation and extinction by > 60 dB. Single-crystal PZTs on silica V-grooves are utilized for the stabilization of the optical cavity with length uncertainty less than 1=100 of a single nucleon, along with extreme level of vibration isolation in a XHV environment. The capability to perform in-situ RF plasma cleaning allows the regeneration of optical mirrors when coated with a few Cs atoms. Lastly but not the least, we combine single-atom resolution quantum gas microscopy technique with superpixel holographic algorithm to project arbitrary real-time recon gurable di raction-limited optical potential landscapes for the preparation of low-entropy atom arrays