Roadmap on structured waves

Structured waves are ubiquitous for all areas of wave physics, both classical and quantum, where the wavefields are inhomogeneous and cannot be approximated by a single plane wave. Even the interference of two plane waves, or a single inhomogeneous (evanescent) wave, provides a number of nontrivial phenomena and additional functionalities as compared to a single plane wave. Complex wavefields with inhomogeneities in the amplitude, phase, and polarization, including topological structures and singularities, underpin modern nanooptics and photonics, yet they are equally important, e.g., for quantum matter waves, acoustics, water waves, etc. Structured waves are crucial in optical and electron microscopy, wave propagation and scattering, imaging, communications, quantum optics, topological and non-Hermitian wave systems, quantum condensed-matter systems, optomechanics, plasmonics and metamaterials, optical and acoustic manipulation, and so forth. This Roadmap is written collectively by prominent researchers and aims to survey the role of structured waves in various areas of wave physics. Providing background, current research, and anticipating future developments, it will be of interest to a wide cross-disciplinary audience.Comment: 110 pages, many figure

Miniaturized Transistors

What is the future of CMOS? Sustaining increased transistor densities along the path of Moore's Law has become increasingly challenging with limited power budgets, interconnect bandwidths, and fabrication capabilities. In the last decade alone, transistors have undergone significant design makeovers; from planar transistors of ten years ago, technological advancements have accelerated to today's FinFETs, which hardly resemble their bulky ancestors. FinFETs could potentially take us to the 5-nm node, but what comes after it? From gate-all-around devices to single electron transistors and two-dimensional semiconductors, a torrent of research is being carried out in order to design the next transistor generation, engineer the optimal materials, improve the fabrication technology, and properly model future devices. We invite insight from investigators and scientists in the field to showcase their work in this Special Issue with research papers, short communications, and review articles that focus on trends in micro- and nanotechnology from fundamental research to applications

Active graphene metasurfaces for optoelectronic applications

Plasmonic metasurfaces are optical components that enhance the light-matter interaction and can control the flow of light. The scalability and universality of the metasurface design enables their deployment across the entire electromagnetic spectrum. Especially attractive are the metasurfaces designed to operate in the mid-infrared part of the optical spectrum. That is due to two factors: the variety of technological applications and the limited choice of conventional optical components in the mid-IR spectral region. Graphene has emerged as a promising optoelectronic material because its optical properties can be rapidly and dramatically changed using electric gating. In particular in the mid-IR regime, graphene has plasmonic properties and can be utilized as a tunable inductor for active modulation of the light with an ultra-fast rate. However graphene’s weak optical response, especially in the infrared part of the spectrum, remains the key challenge to developing practical graphene-based optical devices such as modulators, infrared detectors, and tunable reflect-arrays. In this thesis, we take advantage of plasmonic metasurfaces to enhance the light interaction with graphene for crucial optoelectronic applications. The ability to modulate light at a high-speed is an important part of modern communication systems. We use the plasmonic properties of graphene in the mid-IR range to spectrally shift a narrow-width Fano resonance. Using this approach, we achieve strong modulation of amplitude and phase using plasmonic Fano-resonant metasurfaces integrated with graphene. We also demonstrate that the strong spectral shift of the plasmonic resonance can be used to extract one of the key optical parameters of graphene: the free carrier scattering rate. Another interesting branch of optics is wave-front engineering. The ability to dynamically manipulate the phase, inspires interesting applications such as beam steering and holograms. We use a Michelson interferometry to measure the graphene-induced phase modulation. In particular, we show that it is possible to modulate the phase of electromagnetic wave while the amplitude is constant. We demonstrate proof of concept application of active phase modulation in motion sensing and polarization conversion. An emerging area of optoelectronic is ultra-fast photodetectors based on graphene and other 2-D materials. We employ Full-wave and electrostatic simulations to study the performance of a metasurface-based photodetector. Circuit analysis is utilized to provide a mathematical relation for the responsivity of the metasurface-based graphene photodetector. It is shown that electrically-connected metasurfaces can dramatically enhance the collection efficiency of graphene photodetectors.Physic

Exploring the potential of brain-inspired computing

The gap between brains and computers regarding both their cognitive capability and power efficiency is remarkably huge. Brains process information massively in parallel and its constituents are intrinsically self-organizing, while in digital computers the execution of instructions is deterministic and rather serial. The recent progress in the development of dedicated hardware systems implementing physical models of neurons and synapses enables to efficiently emulate spiking neural networks. In this work, we verify the design and explore the potential for brain-inspired computing of such an analog neuromorphic system, called Spikey. We demonstrate the versatility of this highly configurable substrate by the implementation of a rich repertoire of network models, including models for signal propagation and enhancement, general purpose classifiers, cortical models and decorrelating feedback systems. Network emulations on Spikey are highly accelerated and consume less than 1 nJ per synaptic transmission. The Spikey system, hence, outperforms modern desktop computers in terms of fast and efficient network simulations closing the gap to brains. During this thesis the stability, performance and user-friendliness of the Spikey system was improved integrating it into the neuroscientific tool chain and making it available for the community. The implementation of networks suitable to solve everyday tasks, like object or speech recognition, qualifies this technology to be an alternative to conventional computers. Considering the compactness, computational capability and power efficiency, neuromorphic systems may qualify as a valuable complement to classical computation

Particle Physics Reference Library

This second open access volume of the handbook series deals with detectors, large experimental facilities and data handling, both for accelerator and non-accelerator based experiments. It also covers applications in medicine and life sciences. A joint CERN-Springer initiative, the “Particle Physics Reference Library” provides revised and updated contributions based on previously published material in the well-known Landolt-Boernstein series on particle physics, accelerators and detectors (volumes 21A,B1,B2,C), which took stock of the field approximately one decade ago. Central to this new initiative is publication under full open access

Understanding Quantum Technologies 2022

Understanding Quantum Technologies 2022 is a creative-commons ebook that provides a unique 360 degrees overview of quantum technologies from science and technology to geopolitical and societal issues. It covers quantum physics history, quantum physics 101, gate-based quantum computing, quantum computing engineering (including quantum error corrections and quantum computing energetics), quantum computing hardware (all qubit types, including quantum annealing and quantum simulation paradigms, history, science, research, implementation and vendors), quantum enabling technologies (cryogenics, control electronics, photonics, components fabs, raw materials), quantum computing algorithms, software development tools and use cases, unconventional computing (potential alternatives to quantum and classical computing), quantum telecommunications and cryptography, quantum sensing, quantum technologies around the world, quantum technologies societal impact and even quantum fake sciences. The main audience are computer science engineers, developers and IT specialists as well as quantum scientists and students who want to acquire a global view of how quantum technologies work, and particularly quantum computing. This version is an extensive update to the 2021 edition published in October 2021.Comment: 1132 pages, 920 figures, Letter forma

Tuning resistive switching in complex oxide memristors

The continuous demand of lightweight portable, cheap and low-power devices has pushed the electronic industry to the limits of the current technology. Flash memory technology which represents the mainstream non-volatile memories has experienced an impressive development over the last decade. This led their fabrication down to a 16 nm node and implementation of high-density 3D memory architectures. Due to the scaling limit of Flash technology, the need of new memories that combine the characteristics of a Flash but overcome the scaling limits is increasing. In this surge, oxide-based resistive memories – also called memristors – have emerged as a new family of storage-class memory. The extremely simple physical structure fast response, low cost and power consumption render resistive memories as a valid alternative of the Flash technology and an optimal choice for the next generation memory technology. The nanoscale resistive memories have demonstrated a variety of memory characteristics which depends on the electrochemical properties of the oxide system and several physical parameters including device structure and electrical biasing conditions. This indicates a complex nature of the underlying microscopic switching mechanisms which require a thorough understanding in order to fully benefit from the virtue of this technology. The work presented in this Doctoral Dissertation focuses on the realization and fine tuning the memory characteristics of SrTiO3 based resistive switching memories. A novel synthesis route is adopted to realize highly complementary metal oxide semiconductor (CMOS) compatible nanoscale memristive devices and engineer the composition of the functional SrTiO3 perovskite oxide. By following the novel synthesis approach, SrTiO3 memristive devices with different stoichiometry such as different concentration of oxygen vacancies, metallic dopant species and physical structures are fabricated to achieve multifunctional characteristics of these devices. Rigorous electrical and material characterizations are carried out to analyze the resistive switching performance and understand the underlying microscopic mechanisms. Stable multi-state resistive switching is demonstrated in donor (Nb) doped oxygen-deficient amorphous SrTiO3 (Nb:a-STOx) memories. The dynamics of multi-state switching behavior and the effect of Nb-doping on tuning the resistive switching are investigated by utilizing a combination of interfacial compositional evaluation and activation energy measurements. Furthermore, multiple switching behaviors in a single acceptor (Cr) doped amorphous SrTiO3 (Cr:a-STOx) memory cell are demonstrated. A physical model is also suggested to explain the novel switching characteristics of these versatile memristive devices. A highly transparent and multifunctional SrTiO3 based memory system is fabricated which offers a reliable data storage and photosensitive platform for further transparent electronics. Also a unique photoluminescence mapping is presented as an identification technique for localized conduction mechanism in oxide resistive memories. Finally, SrTiO3 resistive memories are engineered to mimic biological synapses. A hybrid CMOS-memristor approached is presented to demonstrate first implementation of higher order time and rate dependent synaptic learning rules. Furthermore, these artificial synapses are tuned for energy-efficient performance to highlight their potential for the future neuromorphic networks

Dynamic Control of Metamaterials at Terahertz Frequencies

Thesis advisor: Willie J. PadillaProgress in the field of metamaterials has started coming to a point where the field may finally begin to emerge as a viable solution to many electromagnetic challenges facing the community. No where is that more true then at terahertz frequencies where there lies an immense opportunity for growth. The development of mature technologies within this region of the electromagnetic spectrum would provide a valuable resource to become available for a multitude of applications. In order to achieve this, the necessary first steps of identifying viable materials and paths to integrate these with metamaterials will need to be completed. In this dissertation, we examine several different paths to achieve dynamic metamaterial electromagnetic response at terahertz frequencies, and demonstrate several paths to package these devices into imaging systems. In Chapter 1, we introduce the basic theory and design principles of metamaterials. We also describe the experimental techniques involved in the study of terahertz metamaterials. Chapter 2 presents a computational and experimental study investigating the integration of high electron mobility transistors with metamaterials allowing for high speed modulation of incident terahertz radiation. In Chapters 3 and 4, we investigate several different paths to create tunable terahertz metamaterial absorbers. Chapter 3 presents an investigation where we encapsulate a metametarial absorber unit cell with liquid crystals. We study both computationally and experimentally the tuning mechanism of the absorber as the liquid crystal refractive index is controlled as a function of the applied electric field strength and modulation frequency. In Chapter 4, we form a doped semiconducting metamaterial spatial light modulator with multi-color super-pixels composed of arrays of electronically controlled terahertz metamaterial absorbers. We computationally and experimentally study the independent tunability of each pixel in the spatial array and demonstrate high speed modulation. Chapter 5 introduces a multiplex imaging approach by using a terahertz spatial light modulator to enable terahertz imaging with a single pixel detector. We demonstrate the capability for high speed image acquisition, currently only limited by the commerical software used to reconfigure the spatial masks. We also configure the system to capture high fidelity images of varying complexity. In Chapter 6, we show how a metamaterial absorber can be implemented into a detector focal plane array for high sensitivity, low mutual coupling, and broad angle performance. Finally, we summarize in Chapter 7 the achievments of the research presented and highlight the direction of future work.Thesis (PhD) — Boston College, 2013.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Physics