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Conference on Lasers and Electro-Optics (CLEO)

作者： Tristan Melton Alwaleed Aldhafeeri Hsiao Hsuan Chin Lala Rukh Gabriel M. Colación Tara E. Drake Chee Wei Wong Mesoscopic Optics and Quantum Electronics Laboratory University of California Los Angeles CA USA Optical Science & Engineering Program Center for High Technology Materials University of New Mexico Albuquerque NM USA Dept. of Physics & Astronomy University of New Mexico Albuquerque NM USA

We design microresonators for octave-spanning soliton frequency comb generation in silicon nitride. We lock the repetition rate via an electro-optic comb and achieve phase noise of -130-dBc/Hz, with the resultant modu... 详细信息

ISBN: (纸本)9798350369311

关键词： Phase noise Frequency modulation Laser noise Silicon nitride Solitons Electro-optic modulators Electro-optic effects Microcavities

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Ground state phases of the two-dimension electron gas with a unified variational approach

arXiv

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arXiv 2024年

作者： Smith, Conor Chen, Yixiao Levy, Ryan Yang, Yubo Morales, Miguel A. Zhang, Shiwei Center for Computational Quantum Physics Flatiron Institute New YorkNY10010 United States Department of Electrical and Computer Engineering University of New Mexico AlbuquerqueNM87131 United States Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

The two-dimensional electron gas (2DEG) is a fundamental model, which is drawing increasing interest because of recent advances in experimental and theoretical studies of 2D materials. Current understanding of the ground state of the 2DEG relies on quantum Monte Carlo calculations, based on variational comparisons of different ansatze for different phases. We use a single variational ansatz, a general backflow-type wave function using a message-passing neural quantum state architecture, for a unified description across the entire density range. The variational optimization consistently leads to lower ground-state energies than previous best results. Transition into a Wigner crystal (WC) phase occurs automatically at rs = 37±1, a density lower than currently believed. Between the liquid and WC phases, the same ansatz and variational search strongly suggest the existence of intermediate states in a broad range of densities, with enhanced short-range nematic spin correlations. Copyright © 2024, The Authors. All rights reserved.

关键词： Message passing

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Terahertz spin dynamics in rare-earth orthoferrites

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Photonics Insights 2022年第2期1卷 1-56页

作者： Xinwei Li Dasom Kim Yincheng Liu Junichiro Kono Department of Physics California Institute of TechnologyPasadenaUSA Department of Electrical and Computer Engineering Rice UniversityHoustonUSA Applied Physics Graduate Program Smalley-Curl InstituteRice UniversityHoustonUSA Department of Physics and Astronomy Rice UniversityHoustonUSA Department of Materials Science and NanoEngineering Rice UniversityHoustonUSA

Recent interest in developing fast spintronic devices and laser-controllable magnetic solids has sparked tremendous experimental and theoretical efforts to understand and manipulate ultrafast dynamics in *** of spin dynamics in the terahertz(THz)frequency range are particularly important for elucidating microscopic pathways toward novel device ***,we review THz phenomena related to spin dynamics in rare-earth orthoferrites,a class of materials promising for antiferromagnetic *** expand this topic into a description of four key elements.(1)We start by describing THz spectroscopy of spin excitations for probing magnetic phase transitions in thermal *** acoustic magnons are useful indicators of spin reorientation transitions,electromagnons that arise from dynamic magnetoelectric couplings serve as a signature of inversion-symmetry-breaking phases at low temperatures.(2)We then review the strong laser driving scenario,where the system is excited far from equilibrium and thereby subject to modifications to the free-energy *** pathways for ultrafast laser manipulation of magnetic order are discussed.(3)Furthermore,we review a variety of protocols to manipulate coherent THz magnons in time and space,which are useful capabilities for antiferromagnetic spintronic applications.(4)Finally,new insights into the connection between dynamic magnetic coupling in condensed matter and the Dicke superradiant phase transition in quantum optics are *** presenting a review on an array of THz spin phenomena occurring in a single class of materials,we hope to trigger interdisciplinary efforts that actively seek connections between subfields of spintronics,which will facilitate the invention of new protocols of active spin control and quantum phase engineering.

关键词： terahertz spin dynamics magnetism orthoferrite ultrafast spectroscopy magneto-optics

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Modifying BiVO4 as a photocatalyst for water oxidation using constant-duration alkaline-etched post treatments

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New Journal of Chemistry 2023年第2期48卷 569-577页

作者： Hsu, Chuan-Chih Chuang, Kai-Jie Huang, Hsiao-Wen Pan, Bo-Jin Chen, Hung-Ming Husain, Sadang Yougbaré, Sibidou Hsiao, Yu-Cheng Wu, Yung-Fu Lin, Lu-Yin Division of Cardiovascular Surgery Department of Surgery School of Medicine College of Medicine Taipei Medical University Taiwan Division of Cardiovascular Surgery Department of Surgery Taipei Medical University Hospital Taiwan Department of Chemical Engineering and Biotechnology National Taipei University of Technology Taipei Taiwan Department of Chemical Engineering Ming Chi University of Technology New Taipei City24301 Taiwan Gingen Technology Co. Ltd. Rm. 7 10F. No. 189 Sec. 2 Keelung Rd. Xinyi Dist. Taipei11054 Taiwan Department of Physics Faculty of Mathematics and Natural Science Lambung Mangkurat University Banjarmasin70124 Indonesia /Nanoro Ouagadougou03 Burkina Faso International PhD Program in Biomedical Engineering College of Biomedical Engineering Taipei Medical University Taipei11031 Taiwan Stanford Byers Center for Biodesign Stanford University CA94305-5428 United States Graduate Institute of Biomedical Optomechatronics College of Biomedical Engineering Taipei Medical University Taipei11031 Taiwan Cell Physiology and Molecular Image Research Center Wan Fang Hospital Taipei Medical University Taipei11696 Taiwan

BiVO4 with suitable band edges and a small band gap is considered an efficient photocatalyst for the oxygen evolution reaction (OER), but short charge-transfer lengths limit its photocatalytic ability. Increasing active sites can essentially enhance oxidation reactions and photocatalytic ability. The alkaline etching technique can refine the surface properties of BiVO4 by introducing oxygen vacancies and possibly establishing a heterojunction, but suitable alkaline etching methods are rarely discussed. In this study, three alkaline etching methods, including hydrothermal, soaking, and electrodeposition processes, are first applied for a constant duration to tailor the surface properties of BiVO4 as a photocatalyst for the OER. Alkaline-etched BiVO4 prepared using hydrothermal and soaking processes shows better photocatalytic abilities due to the generation of additional oxygen vacancies, while poor photocatalytic ability is found for that fabricated using electrodeposition due to the formation of less photocatalytic VO2. The highest photocurrent density of 2.38 mA cm−2 is obtained at 1.23 V versus a reversible hydrogen electrode in an electrolyte without a hole scavenger for the BiVO4 etched in the hydrothermal process, while the untreated BiVO4 presents a photocurrent density of 0.58 mA cm−2. A photocurrent retention of 92.3% is achieved after 5000 seconds of continuous illumination. The study supplies blueprints for establishing effective alkaline etching methods for enhancing the photocatalytic ability of BiVO4, with the exception of time costs. © 2024 The Royal Society of Chemistry.

关键词： Charge transfer

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The Potential of Rooftop Solar Photovoltaic Generation System at The Laboratory Complex of University of Riau

The Potential of Rooftop Solar Photovoltaic Generation Syste...

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International Conference on Electrical engineering and Informatics (ICon EEI)

作者： Nurhalim Dani Ali Syaiful Bahri Yusni Ikhwan Siregar Zulfan Saam Juandi Muhammad Suwondo Suwondo Iswadi Hasyim Rosma Postgraduate Program and Electrical Engineering Dept. Enviromental Science University of Riau Pekanbaru Indonesia Chemical Enginerring Dept. University of Riau Pekanbaru Indonesia Enviromental Sciences Dept. University of Riau Pekanbaru Indonesia Physics Science Dept. University of Riau Pekanbaru Indonesia Electrical Engineering Dept. University of Riau Pekanbaru Indonesia

ISBN: (数字)9798331540791

ISBN: (纸本)9798331540807

Solar photovoltaic (PV) systems are becoming the future type of power plant to meet the electrical energy needs of buildings. The open roof of the building facing the sky has the potential to harvest energy from solar energy. The roof of the Faculty of engineering Laboratory Building at Riau University has the potential to be used to capture solar energy. In this study, the research is focused on designing a comprehensive solar PV system that adapts to the geographical conditions of the campus. The data was calculated using software to design and analyze the rooftop PV system. Meteorological data was collected using an automatic weather station (AWS). The data measured through the AWS includes solar irradiation, temperature, humidity, and wind speed. The data is sampled once every 5 minutes, resulting in 12 data points per hour. The amount of data for one day is 12 multiplied by 24 hours. The total data for one month is obtained by multiplying the daily data by the number of days in the month. In details of this study, the PV panels were installed on the roof space of the Laboratory Building which is grid-connected. In addition, detailed technical analysis including effective roof area, roof orientation, number of panels and power capacity of the proposed PV were analyzed. As the result an effective roof area of 1,510.500 m2, the total number of panels of 656 pieces, the total power capacity of 229,600 Wp, and the total amount of energy generated by the module array of 160,545 kWh per year were achieved respectively. The energy delivered to the grid amounted to as much as 155,414 kWh per year. The specific energy generated was 677 kWh/KWp/year and the Performance Ratio (PR) reached 82%.

关键词： Temperature measurement Photovoltaic systems Electrical engineering Electric potential Wind speed Buildings Solar energy Software Inverters Solar radiation

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Ab initio phonon transport across grain boundaries in graphene using machine learning based on small dataset

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Physical Review Materials 2022年第4期6卷 044004-044004页

作者： Amirreza Hashemi Ruiqiang Guo Keivan Esfarjani Sangyeop Lee Computational Modeling and Simulation Program University of Pittsburgh Pittsburgh Pennsylvania 15261 USA Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh Pennsylvania 15261 USA Department of Mechanical and Aerospace Engineering University of Virginia Charlottesville Virginia 22904 USA Department of Materials Science and Engineering University of Virginia Charlottesville Virginia 22904 USA Department of Physics University of Virginia Charlottesville Virginia 22904 USA Department of Physics and Astronomy University of Pittsburgh Pittsburgh Pennsylvania 15261 USA

Establishing the structure-property relationship for grain boundaries (GBs) is critical for developing next-generation functional materials but has been severely hampered due to its extremely large configurational space. Atomistic simulations with low computational cost and high predictive power are strongly desirable, but the conventional simulations using empirical interatomic potentials and density functional theory suffer from the lack of predictive power and high computational cost, respectively. A machine learning interatomic potential (MLIP) recently emerged but often requires extensive size of the training dataset, making it a less feasible approach. Here, we demonstrate that an MLIP trained with a rationally designed small training dataset can predict thermal transport across GBs in graphene with ab initio accuracy at an affordable computational cost. We employed a rational approach based on the structural unit model to find a small set of GBs that can represent the entire configurational space and thus can serve as a cost-effective training dataset for the MLIP. Only 5 GBs were found to be enough to represent the entire configurational space of graphene GBs. Using the atomistic Green's function approach and the MLIP, we revealed that the structure-thermal resistance relation in graphene does not follow the common understanding that large dislocation density causes larger thermal resistance. In fact, thermal resistance is nearly independent of dislocation density at room temperature and is higher when the dislocation density is small at sub-room temperature. We explain this intriguing behavior with the buckling near a GB causing a strong scattering of flexural phonon modes. In this paper, we show that a machine learning technique combined with conventional wisdom (e.g., structural unit model) can extend the recent success of ab initio thermal transport simulation, which has been mostly limited to single crystals, to complex yet practically important polycry

关键词： Phonons Graphene Landauer formula Machine learning

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Chiral, Topological, and Knotted Colloids in Liquid Crystals

arXiv

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arXiv 2024年

作者： Yuan, Ye Smalyukh, Ivan I. Hiroshima University Hiroshima Higashi-Hiroshima739-8526 Japan Department of Physics Department of Electrical Computer and Energy Engineering Materials Science and Engineering Program Soft Materials Research Center University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States

The geometric shape, symmetry, and topology of colloidal particles often allow for controlling colloidal phase behavior and physical properties of these soft matter systems. In liquid crystalline dispersions, colloidal particles with low symmetry and nontrivial topology of surface confinement are of particular interest, including surfaces shaped as handlebodies, spirals, knots, multi-component links, and so on. These types of colloidal surfaces induce topologically nontrivial three-dimensional director field configurations and topological defects. Director switching by electric fields, laser tweezing of defects, and local photo-thermal melting of the liquid crystal host medium promote transformations among many stable and metastable particle-induced director configurations that can be revealed by means of direct label-free three-dimensional nonlinear optical imaging. The interplay between topologies of colloidal surfaces, director fields, and defects is found to show a number of unexpected features, such as knotting and linking of line defects, often uniquely arising from the nonpolar nature of the nematic director field. This review article highlights fascinating examples of new physical behavior arising from the interplay of nematic molecular order and both chiral symmetry and topology of colloidal inclusions within the nematic host. Furthermore, the article concludes with a brief discussion of how these findings may lay the groundwork for new types of topology-dictated self-assembly in soft condensed matter leading to novel mesostructured composite materials, as well as for experimental insights into the pure-math aspects of low-dimensional topology. © 2024, CC BY.

关键词： Crystal symmetry

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Quantum aspects of hydrodynamic transport from weak electron-impurity scattering

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Physical Review B 2020年第12期101卷 121107(R)-121107(R)页

作者： Aaron Hui Samuel Lederer Vadim Oganesyan Eun-Ah Kim School of Applied & Engineering Physics Cornell University Ithaca New York 14853 USA Department of Physics Cornell University Ithaca New York 14853 USA Department of Physics and Astronomy College of Staten Island CUNY Staten Island New York 10314 USA Physics Program and Initiative for the Theoretical Sciences The Graduate Center CUNY New York New York 10016 USA

Recent experimental observations of apparently hydrodynamic electronic transport have generated much excitement. However, the understanding of the observed nonlocal transport (whirlpool) effects and parabolic (Poiseuille-like) current profiles has largely been motivated by a phenomenological analogy to classical fluids. This is due to difficulty in incorporating strong correlations in quantum mechanical calculation of transport, which has been the primary angle for interpreting the apparently hydrodynamic transport. Here we demonstrate that even free-fermion systems, in the presence of (inevitable) disorder, exhibit nonlocal conductivity effects such as those observed in experiments because of the fermionic system's long-range entangled nature. On the basis of explicit calculations of the conductivity at finite wave vector, σ(q), for selected weakly disordered free-fermion systems, we propose experimental strategies for demonstrating distinctive quantum effects in nonlocal transport at odds with the expectations of classical kinetic theory. Our results imply that the observation of whirlpools or other “hydrodynamic” effects does not guarantee the dominance of electron-electron scattering over electron-impurity scattering.

关键词： Electrical conductivity Quantum field theory Disordered systems Hydrodynamics

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Electronic-photonic quantum systems on-chip

Electronic-photonic quantum systems on-chip

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Quantum 2.0, QUANTUM 2022

作者： Wang, Imbert Ramesh, Anirudh Kramnik, Danielius Fargas Cabanillas, Josep M. Stojanović, Vladimir Kumar, Prem Popović, Miloš A. Department of Electrical and Computer Engineering Photonics Center Boston University BostonMA02215 United States Graduate Program in Applied Physics Northwestern University EvanstonIL60208 United States Department of Electrical Engineering and Computer Science UC Berkeley BerkeleyCA94720 United States Center for Photonic Communication and Computing Dept. of Electrical and Computer Eng. Northwestern University EvanstonIL60208 United States

We present progress towards realizing electronic-photonic quantum systems on-chip;particularly, entangled photon-pair sources, placing them in the context of previous work, and outlining our vision for mass-producible... 详细信息

ISBN: (纸本)9781957171111

关键词： Quantum entanglement

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Overcoming intensity saturation in second harmonic nonlinear intersubband polaritonic metasurfaces using two-level systems 13

Overcoming intensity saturation in second harmonic nonlinear...

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Photonic and Phononic Properties of Engineered Nanostructures XIII 2023

作者： Krakofsky, Jonas H. Stich, Simon Cotrufo, Michele Mekawy, Ahmed Mann, Sander A. Köninger, Anna Boehm, Gerhard Alù, Andrea Belkin, Mikhail A. Walter Schottky Institute Technical University of Munich GarchingD-85748 Germany Photonics Initiative Advanced Science Research Center City University of New York New YorkNY10031 United States Physics Program Graduate Center City University of New York New YorkNY10016 United States Department of Electrical Engineering City College The City University of New York New YorkNY10031 United States

ISBN: (纸本)9781510659674

Nonlinear metasurfaces based on coupling of intersubband transitions in n-doped semiconductor heterostructures with optical modes in nanoresonators provide the largest known second-order nonlinear response in condensed matter systems in the mid-infrared spectral range. However, these giant nonlinearities are only present at relatively low pumping intensities which limits the maximum achievable frequency conversion efficiency. We experimentally investigate a new nonlinear intersubband metasurface design for second harmonic generation based on two-level nonlinear intersubband system that provides high nonlinearity combined with significantly reduced intensity saturation compared to the intersubband metasurfaces based on three-level intersubband systems demonstrated so far. © 2023 SPIE.

关键词： Harmonic generation

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