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arXiv 2020年

作者： Hallman, Kent A. Miller, Kevin J. Baydin, Andrey Weiss, Sharon M. Haglund, Richard F. Department of Physics and Astronomy Vanderbilt University NashvilleTN37235 United States Interdisciplinary Graduate Program in Materials Science NashvilleTN37235 United States Department of Electrical Engineering and Computer Science Vanderbilt University NashvilleTN37235 United States AEgis Technologies Group 410 Jan Davis Drive HuntsvilleAL35803 United States Department of Electrical and Computer Engineering Rice University HoustonTX70005 United States

Achieving ultrafast all-optical switching in a silicon waveguide geometry is a key milestone on the way to an integrated platform capable of handling the increasing demands for higher speed and higher capacity for information transfer. Given the weak electro-optic and thermo-optic effects in silicon, there has been intense interest in hybrid structures in which that switching could be accomplished by integrating another material into the waveguide, including the phase-changing material, vanadium dioxide (VO2). It has long been known that the phase transition in VO2 can be triggered by ultrafast laser pulses, and that pump-laser fluence is a critical parameter governing the recovery time of thin films irradiated by femtosecond laser pulses near 800 nm. However, thin-film experiments are not a priori reliable guides to using VO2 for all-optical switching in on-chip silicon photonics because of the large changes in VO2 optical constants in the telecommunications band, the requirement of low insertion loss, and the limits on switching energy permissible in integrated photonic systems. Here we report the first measurements to show that the reversible, ultrafast photo-induced phase transition in VO2 can be harnessed to achieve sub-picosecond switching when small VO2 volumes are integrated in a silicon waveguide as a modulating element. Switching energies above threshold are of order 600 fJ/switch. These results suggest that VO2 can now be pursued as a strong candidate for all-optical switching with sub-picosecond on-off times. Copyright © 2020, The Authors. All rights reserved.

关键词： Optical switches

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Machine Learning-Based Statistical Hypothesis Testing for Fault Detection

Machine Learning-Based Statistical Hypothesis Testing for Fa...

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Conference on Control and Fault-Tolerant Systems (SysTol)

作者： Radhia Fazai Majdi Mansouri Kamal Abodayeh Mohamed Trabelsi Hazem Nounou Mohamed Nounou Electrical and Computer Engineering Program Texas A&M University at Qatar Doha Qatar Department of Mathematical Sciences Prince Sultan University Riyadh Saudi Arabia Department of Electronic and Communications Engineering Kuwait College of Science and Technology Kuwait Chemical Engineering Program Texas A&M University at Qatar Doha Qatar

ISBN: (纸本)9781728103815

This paper elaborates the development of machine learning approach merged with statistical hypothesis testing aimed at enhancing the operation of photovoltaic (PV) systems by developing intelligent PV fault detection framework. Fault detection in PV systems is important to ensure optimal energy harvesting and reliable power production because PV systems usually operate in a harsh outdoor environment and tend to suffer various faults. In this paper, therefore, special attention is paid to detection of various faults during different modes of operation. The proposed approach merges the benefits of machine learning technique (MLT) with statistical hypothesis testing to enhance the fault detection and monitoring of PV systems. The proposed technique will be effective in monitoring the PV faults under both normal and abnormal conditions. For the framework developed, the modeling phase is addressed using MLT and the faults are detected using the generalized likelihood ratio test (GLRT) chart. The MLT is used to compute the residuals monitored and the GLRT chart is applied to the monitored residuals evaluated for fault detection purposes. The developed MLT-based GLRT algorithm is implemented and validated using both simulated and real PV data. The results are evaluated in terms of false alarm rates (FAR), missed detection rates (MDR) and computation time.

关键词： Ground penetrating radar Monitoring Circuit faults Testing Photovoltaic systems Fault detection

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electrically injected AlGaN nanowire deep ultraviolet lasers

Electrically injected AlGaN nanowire deep ultraviolet lasers

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IEEE Photonics Conference (IPC)

作者： Z. Mi S. Zhao X. Liu S. Y. Woo M. Bugnet G. A. Botton Department of Electrical and Computer Engineering McGill University Montreal Quebec Canada Department of Materials Science and Engineering and Canadian Centrefor Electron Microscopy McMaster University Hamilton ON Canada McMaster University Michael G DeGroote School of Medicine Hamilton ON CA

We report on the demonstration of AlGaN nanowire lasers in the ultraviolet (UV)-B and UV-C bands. The AlGaN nanowires were grown directly on Si substrate and were characterized by the presence of quantum-dot-like nano... 详细信息

ISBN: (纸本)9781509019076

关键词： Aluminum gallium nitride Wide band gap semiconductors Temperature measurement Silicon Optical scattering Optical pumping

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Lattice-Matched Multiple Channel AlScN/GaN Heterostructures

arXiv

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arXiv 2024年

作者： Nguyen, Thai-Son Pieczulewski, Naomi Savant, Chandrashekhar Cooper, Joshua J.P. Casamento, Joseph Goldman, Rachel S. Muller, David A. Xing, Huili G. Jena, Debdeep Department of Materials Science and Engineering Cornell University IthacaNY14853 United States Department of Materials Science and Engineering University of Michigan Ann ArborMI48109 United States Department of Materials Science and Engineering Massachusetts Institute of Technology CambridgeMA02139 United States Kavli Institute at Cornell for Nanoscale Science Cornell University IthacaNY14853 United States School of Applied and Engineering Physics Cornell University IthacaNY14853 United States Department of Electrical and Computer Engineering Cornell University IthacaNY14853 United States

AlScN is a new wide bandgap, high-k, ferroelectric material for RF, memory, and power applications. Successful integration of high quality AlScN with GaN in epitaxial layer stacks depends strongly on the ability to control lattice parameters and surface or interface through growth. This study investigates the molecular beam epitaxy growth and transport properties of AlScN/GaN multilayer heterostructures. Single layer Al1−xScxN/GaN heterostructures exhibited lattice-matched composition within x = 0.09 – 0.11 using substrate (thermocouple) growth temperatures between 330 ◦C and 630 ◦C. By targeting the lattice-matched Sc composition, pseudomorphic AlScN/GaN multilayer structures with ten and twenty periods were achieved, exhibiting excellent structural and interface properties as confirmed by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). These multilayer heterostructures exhibited substantial polarization-induced net mobile charge densities of up to 8.24 × 1014/cm2 for twenty channels. The sheet density scales with the number of AlScN/GaN periods. By identifying lattice-matched growth condition and using it to generate multiple conductive channels, this work enhances our understanding of the AlScN/GaN material platform. © 2024, CC BY.

关键词： Thermocouples

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Molecular dynamic simulation of heat pulse propagation in multiwall carbon nanotubes

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Physical Review B 2007年第15期76卷 155424-155424页

作者： Taejin Kim Mohamed A. Osman Cecilia D. Richards David F. Bahr Robert F. Richard Material Science Program Washington State University Pullman Washington 99164-4620 USA Department of Physics Washington State University Pullman Washington 99164-2814 USA School of Electrical Engineering and Computer Science Washington State University Pullman Washington 99164-2752 USA School of Mechanical and Materials Engineering Washington State University Pullman Washington 99164-2920 USA

The propagation of heat pulses in zigzag and armchair double wall nanotubes (DWNTs) has been investigated using molecular dynamics simulations. It is found that the leading heat wave packets in zigzag (9,0)∕(18,0) and armchair (5,5)∕(10,10) DWNTs move with the speed of longitudinal acoustic (LA) phonon modes. The intensities of the leading heat wave packets in outer and inner shells in DWNTs were found to be five to seven times larger than that of the corresponding single wall nanotubes (SWNTs). The heat energy carried by the leading heat wave packets in zigzag DWNT was about four and five times more than those in armchair DWNT shells. Within the leading LA wave packet, the strain in the inner shell of the DWNTs is stronger than the strain in the outer shell and considerably larger than strain in the corresponding SWNTs. The regions with the largest strain coincide with the regions of high kinetic temperatures within the LA mode wave packets. The higher energy of the LA mode waves in DWNT shells compared to SWNT is attributed to the presence of higher strain fields in DWNTs compared to individual SWNTs. The higher strain in the inner shell of DWNT compared to the outer shell accounts for the three to five times higher kinetic energy of leading wave packets in inner shells compared to those in outer shells. The induced strain fields in zigzag DWNT are distributed over a wider region compared to armchair DWNT, and the strains in inner and outer shells of zigzag DWNT are out phase by 180°.

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Multifunctional Spin Logic Operations in Graphene Spin Circuits

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Physical Review Applied 2022年第6期18卷 064063-064063页

作者： Dmitrii Khokhriakov Shehrin Sayed Anamul Md. Hoque Bogdan Karpiak Bing Zhao Supriyo Datta Saroj P. Dash Department of Microtechnology and Nanoscience Chalmers University of Technology SE-41296 Göteborg Sweden Department of Electrical Engineering and Computer Sciences University of California-Berkeley Berkeley California 94720 USA Materials Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Electrical and Computer Engineering Purdue University West Lafayette Indiana 47907 USA Graphene Center Chalmers University of Technology SE-41296 Göteborg Sweden

Spin-based computing, combining logic and nonvolatile magnetic memory, is promising for emerging information technologies. However, the realization of a universal spin logic operation, representing a reconfigurable building block with all-electrical spin-current communication, has so far remained challenging. Here, we experimentally demonstrate reprogrammable all-electrical multifunctional spin logic operations in a nanoelectronic device architecture, utilizing graphene buses for spin communication and mixing and nanomagnets for writing and reading information at room temperature. This device realizes a multistate spin-majority logic operation, which is reconfigured to achieve (n)and, (n)or, and xnor Boolean operations, depending on the magnetization of inputs. The results are in good agreement with the predictions from a spin-circuit model, providing an experimental demonstration of a spin-based logic unit that takes advantage of the vector nature of spin, as opposed to conventional scalar charge-based devices. These spin logic operations in large-area graphene are fully compatible with industrial fabrication processes and represent a promising platform for scalable all-electric spin-based logic-in-memory computing architecture.

关键词： Magnetotransport Spin current Devices for digital logic, storage & processing Graphene Nanotechnology

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Wide field-of-view flat lens: An analytical formalism

arXiv

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arXiv 2021年

作者： Yang, Fan Sensong, An Shalaginov, Mikhail Y. Hualiang, Zhang Hu, Juejun Gu, Tian Department of Materials Science and Engineering Massachusetts Institute of Technology CambridgeMA02139 United States Department of Electrical and Computer Engineering University of Massachusetts Lowell LowellMA01854 United States Materials Research Laboratory Massachusetts Institute of Technology CambridgeMA02139 United States

Wide field-of-view (FOV) optics are widely used in various imaging, display, and sensing applications. While conventional wide FOV optics rely on cascading multiple elements to suppress coma and other aberrations, it has recently been demonstrated that diffractionlimited, near-180° FOV operation can be achieved with a single-piece flat fisheye lens designed via iterative numerical optimization [Nano Lett. 20, 7429(2020)]. Here we derive an analytical formalism to enable physics-informed and computationally efficient design of wide FOV flat lenses based on metasurfaces or diffractive optical elements (DOEs). Leveraging this analytical approach, we further quantified trade-offs between optical performance and design parameters in wide FOV metalenses. Copyright © 2021, The Authors. All rights reserved.

关键词： Economic and social effects

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Entanglement-enhanced Optomechanical Sensing

Entanglement-enhanced Optomechanical Sensing

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Conference on Lasers and Electro-Optics (CLEO)

作者： Yi Xia Aman R. Agrawal Christian M. Pluchar Quntao Zhuang Dalziel J. Wilson Zheshen Zhang James C. Wyant College of Optical Sciences University of Arizona Tucson Arizona USA Department of Materials Science and Engineering University of Arizona Tucson Arizona USA Department of Electrical and Computer Engineering University of Arizona Tucson Arizona USA

We experimentally demonstrate entanglement-enhanced optomechanical sensing in which entangled optical probes jointly read out the displacements of two mechanical membranes, enabling enhanced force sensitivities and en... 详细信息

ISBN: (数字)9781957171050

ISBN: (纸本)9781665466660

关键词： Sensitivity Force measurement Force Measurement by laser beam Displacement measurement Optical variables measurement Lasers and electrooptics

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Topology-Preserving Nonlinear Structured Light Generation from All-Dielectric Metasurfaces

Topology-Preserving Nonlinear Structured Light Generation fr...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Jiannan Gao Dmitrii Tsvetkov Danilo Gomes M Pires Yun Xu Ivan Kravchenko Liang Feng Natalia M. Litchinitser Department of Electrical and Computer Engineering Duke University Durham NC USA Dassault Systemes Simulia Corp (CST) Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN USA Department of Materials Science and Engineering University of Pennsylvania Philadelphia PA USA

We experimentally demonstrate the simultaneous generation of phase-locked structured light beams, including optical vortices, Hopf links, and trefoil knots at fundamental and tripled frequencies in all-dielectric nonl... 详细信息

ISBN: (纸本)9781957171258

关键词： Laser beams Light beams Optical vortices Quantum optics Structured light Vortex beams

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Direct observation of site-specific dopant substitution in Si doped (AlxGa1-x)2O3 via atom probe tomography

arXiv

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arXiv 2020年

作者： Sarker, Jith Anhar Uddin Bhuiyan, A.F.M. Feng, Zixuan Zhao, Hongping Mazumder, Baishakhi Department of Materials Design and Innovation University at Buffalo BuffaloNY14260 United States Depertment of Electrical and Computer Engineering Ohio State University ColumbusOH43210 United States Department of Materials Science and Engineering Ohio State University ColumbusOH43210 United States

In this work, the interaction of n-type dopants in Si doped (AlxGa1-x)2O3 films with varying Al content over the entire composition range (x = 0-100%) was analyzed using atom probe tomography. An almost uniform dopant distribution with dopant density in the range of 1018 cm-3 was obtained in all (AlxGa1-x)2O3 layers containing different Al contents. We have demonstrated that for the single phase β-(AlxGa1-x)2O3 films with Al content of x0.50) (AlxGa1-x)2O3 layers. It was also observed for Al content, x = 0.30-0.50, no specific cationic site occupancy was observed, Si occupies either Al or Ga sites. This can be attributed to highly inhomogeneous layers within this composition range due to which dopant Si atoms are either in the Al-rich or Al-depleted regions. Copyright © 2020, The Authors. All rights reserved.

关键词： Atoms

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