检索结果-内蒙古大学图书馆

arXiv 2017年

作者： Liu, Henan Zhang, Yong Steenbergen, Elizabeth H. Liu, Shi Lin, Zhiyuan Zhang, Yong-Hang Kim, Jeomoh Ji, Mi-Hee Detchprohm, Theeradetch Dupuis, Russell D. Kim, Jin K. Hawkins, Samuel D. Klem, John F. Optical Science and Engineering Graduate Program Department of Electrical and Computer Engineering University of North Carolina at Charlotte Charlotte NC United States Center for Photonics Innovation and School of Electrical Computer and EnergyEngineering Arizona State University Tempe AZ United States Center for Compound Semiconductors and School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA United States Sandia National Laboratories Albuquerque NM United States

InAs/InAs1-xSbx superlattice system differ distinctly from two well-studied superlattice systems GaAs/AlAs and InAs/GaSb, in terms of electronic band alignment, common-element at the interface, and phonon spectrum overlapping of the constituents. This fact leads to unique electronic and vibrational properties of the InAs/InAs1-xSbx system when compared to the other two systems. In this work, we report a polarized Raman study on the vibrational properties of the InAs/InAs1-xSbx SLs as well as selected InAs1-xSbx alloys, all grown on GaSb substrates by either MBE or MOCVD, from both growth surface and cleaved edge. In the SL, from the (001) backscattering geometry, an InAs-like LO mode is observed as the primary feature and its intensity is found to increase with increasing Sb composition;from the (110) cleaved edge backscattering geometry, an InAs-like TO mode is observed as the main feature in two cross-polarization configurations, but an additional InAs-like "forbidden" LO mode was observed in two parallel-polarization configurations. InAs1-xSbx alloys lattice-matched to the substrate (xSb ~ 0.09) grown by MBE were also found to exhibit the "forbidden" LO mode, implying the existence of some unexpected [001] modulation, but the strained xSb ~ 0.35 samples grown by MOCVD were found to behavior like a disordered alloy. The primary conclusions are (1) the InAs-like LO or TO mode could be either a confined or quasi-confined mode in the InAs layers of the SL or extended mode of the whole structure, depending on the Sb composition;(2) InAs/InAsSb and InAs/GaSb SLs exhibit significantly different behaviors in the cleaved edge geometry, but qualitatively similar in the (001) geometry;and (3) the appearance of the "forbidden" LO-like mode is a universal signature for SLs and bulk systems resulting from mixing of phonon modes due to structural modulation or symmetry reduction. Copyright © 2017, The Authors. All rights reserved.

关键词： III-V semiconductors

来源：评论

学校读者我要写书评

暂无评论

Riemann-Encircling Exceptional Points for Efficient Asymmetric Polarization-Locked Devices

引用

Physical Review Letters 2022年第12期129卷 127401-127401页

作者： Aodong Li Weijin Chen Heng Wei Guowei Lu Andrea Alù Cheng-Wei Qiu Lin Chen Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information Huazhong University of Science and Technology Wuhan 430074 China Department of Electrical and Computer Engineering National University of Singapore Singapore 117583 Singapore State Key Laboratory for Mesoscopic Physics School of Physics Peking University Beijing 100871 China Photonics Initiative Advanced Science Research Center City University of New York New York New York 10031 USA Physics Program Graduate Center City University of New York New York New York 10016 USA

Dynamically encircling exceptional points (EPs) have unveiled intriguing chiral dynamics in photonics. However, the traditional approach based on an open manifold of Hamiltonian parameter space fails to explore trajectories that pass through an infinite boundary. Here, by mapping the full parameter space onto a closed manifold of the Riemann sphere, we introduce a framework to describe encircling-EP loops. We demonstrate that an encircling trajectory crossing the north vertex can realize near-unity asymmetric transmission. An efficient gain-free, broadband asymmetric polarization-locked device is realized by mapping the encircling path onto L-shaped silicon waveguides.

关键词： PT-symmetric quantum mechanics Photonics

来源：评论

学校读者我要写书评

暂无评论

Assembly of CdSeS(ZnS) quantum dots in langmuir films with tertiary alkyl phosphine ligands

Assembly of CdSeS(ZnS) quantum dots in langmuir films with t...

引用

Nanotechnology - General - 214th ECS Meeting/PRiME 2008

作者： Giles, Alexander J. Pagan, J. Patel, K. Stokes, E.B. Nanoscale Science Graduate Program Department of Chemistry University of North Carolina at Charlotte 9201 University City Boulevard Charlotte NC 28223 United States Dot Metrics Technologies Charlotte Research Institute University of North Carolina at Charlotte 9201 University City Boulevard Charlotte NC 28223 United States Department of Electrical and Computer Engineering University of North Carolina at Charlotte 9201 University City Boulevard Charlotte NC 28223 United States Center for Optoelectronics and Optical Communications University of North Carolina al Charlotte 9201 University City Boulevard Charlotte NC 28223 United States

ISBN: (纸本)9781615672998

The focus of this paper is to describe studies on pre-prepared hydrophobic CdSeS(ZnS) quantum dots (QDs) at the air-water interface. Surface pressure-area (π-A) isotherms were extensively studied using QDs capped with either trioclylphosphine oxide or triethylphosphine oxide. The role of these two different ligands on monolayer behavior and thin film quality has been investigated using the Langmuir-Blodgett (LB) technique. The thin films were characterized by scanning electron microscopy (SEM), fluorescence spectroscopy, and UV-vis spectroscopy. ©The Electrochemical Society.

关键词： Cadmium compounds

来源：评论

学校读者我要写书评

暂无评论

Shape-dependent dispersion and alignment of nonaggregating plasmonic gold nanoparticles in lyotropic and thermotropic liquid crystals

引用

Physical Review E 2014年第5期89卷 052505-052505页

作者： Qingkun Liu Jianwei Tang Yuan Zhang Angel Martinez Shaowei Wang Sailing He Timothy J. White Ivan I. Smalyukh Department of Physics and Materials Science and Engineering Program University of Colorado at Boulder Boulder Colorado 80309 USA Centre for Optical and Electromagnetic Research Zhejiang University Hangzhou 310058 People's Republic of China Air Force Research Laboratory Materials and Manufacturing Directorate WPAFB OH USA Department of Electrical Computer and Energy Engineering and Liquid Crystals Materials Research Center University of Colorado at Boulder Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado Boulder Colorado 80309 USA

We use both lyotropic liquid crystals composed of prolate micelles and thermotropic liquid crystals made of rod-like molecules to uniformly disperse and unidirectionally align relatively large gold nanorods and other complex-shaped nanoparticles at high concentrations. We show that some of these ensuing self-assembled orientationally ordered soft matter systems exhibit polarization-dependent plasmonic properties with strongly pronounced molar extinction exceeding that previously achieved in self-assembled composites. The long-range unidirectional alignment of gold nanorods is mediated mainly by anisotropic surface anchoring interactions at the surfaces of gold nanoparticles. Polarization-sensitive absorption, scattering, and extinction are used to characterize orientations of nanorods and other nanoparticles. The experimentally measured unique optical properties of these composites, which stem from the collective plasmonic effect of the gold nanorods with long-range order in a liquid crystal matrix, are reproduced in computer simulations. A simple phenomenological model based on anisotropic surface interaction explains the alignment of gold nanorods dispersed in liquid crystals and the physical underpinnings behind our observations.

关键词： LYOTROPIC liquid crystals PLASMONS (Physics) GOLD nanoparticles MICELLES NANORODS COMPOSITE materials

来源：评论

学校读者我要写书评

暂无评论

Resolving spin, valley, and moiré quasi-angular momentum of interlayer excitons in WSe2/WS2 heterostructures

arXiv

引用

arXiv 2019年

作者： Jin, Chenhao Regan, Emma C. Wang, Danqing Iqbal Bakti Utama, M. Yang, Chan-Shan Cain, Jeffrey Qin, Ying Shen, Yuxia Zheng, Zhiren Watanabe, Kenji Taniguchi, Takashi Tongay, Sefaattin Zettl, Alex Wang, Feng Department of Physics University of California at Berkeley BerkeleyCA94720 United States Graduate Group in Applied Science and Technology University of California at Berkeley BerkeleyCA94720 United States Department of Materials Science and Engineering University of California at Berkeley BerkeleyCA94720 United States Institute of Electro-Optical Science and Technology Undergraduate Program of Electro-Optical Engineering National Taiwan Normal University Taipei11677 Taiwan Material Science Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Kavli Energy NanoSciences Institute University of California Berkeley Lawrence Berkeley National Laboratory BerkeleyCA94720 United States School for Engineering of Matter Transport and Energy Arizona State University TempeAZ85287 United States National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan

Moiré superlattices provide a powerful way to engineer properties of electrons and excitons in two-dimensional van der Waals heterostructures1-11. The moiré effect can be especially strong for interlayer excitons, where electrons and holes reside in different layers and can be addressed separately. In particular, it was recently proposed that the moiré superlattice potential not only localizes interlayer exciton states at different superlattice positions, but also hosts an emerging moiré quasi-angular momentum (QAM) that periodically switches the optical selection rules for interlayer excitons at different moiré sites12,13. Here we report the observation of multiple interlayer exciton states coexisting in a WSe2/WS2 moiré superlattice and unambiguously determine their spin, valley, and moiré QAM through novel resonant optical pump-probe spectroscopy and photoluminescence excitation spectroscopy. We demonstrate that interlayer excitons localized at different moiré sites can exhibit opposite optical selection rules due to the spatially-varying moiré QAM. Our observation reveals new opportunities to engineer interlayer exciton states and valley physics with moiré superlattices for optoelectronic and valleytronic applications. Copyright © 2019, The Authors. All rights reserved.

关键词： Angular momentum

来源：评论

学校读者我要写书评

暂无评论

High-Order Nonlinear Electrophoresis in a Nematic Liquid Crystal

引用

Physical Review Letters 2024年第15期132卷 158102-158102页

作者： Mojtaba Rajabi Taras Turiv Bing-Xiang Li Hend Baza Dmitry Golovaty Oleg D. Lavrentovich Advanced Materials and Liquid Crystal Institute Kent State University Kent Ohio 44242 USA Department of Physics Kent State University Kent Ohio 44242 USA College of Electronic and Optical Engineering & College of Flexible Electronics (Future Technology) Nanjing University of Posts and Telecommunications Nanjing 210023 China Department of Mathematics The University of Akron Akron Ohio 44325-4002 USA Materials Science Graduate Program Kent State University Kent Ohio 44242 USA

Electrophoresis is the motion of particles relative to a surrounding fluid driven by a uniform electric field. In conventional electrophoresis, the electrophoretic velocity grows linearly with the applied field. Nonlinear effects with a quadratic speed vs field dependence are gaining research interest since an alternating current field could drive them. Here, we report on the giant nonlinearity of electrophoresis in a nematic liquid crystal in which the speed grows with the fourth and sixth powers of the electric field. The mechanism is attributed to the shear thinning of the nematic environment induced by the moving colloid. The observed giant nonlinear effect dramatically enhances the efficiency of electrophoretic transport.

关键词： Electrophoresis Non-Newtonian fluids Nonlinear dynamics in fluids Colloids Liquid crystals Nematic liquid crystals optical microscopy Rheology techniques

来源：评论

学校读者我要写书评

暂无评论

Effect of Growth Pressure and Gas-Phase Chemistry on the optical Quality of InGaN/GaN Multi-Quantum Wells

引用

MRS Online Proceedings Library (OPL) 2013年第1期1538卷 341-351页

作者： E.A. Armour D. Byrnes R.A. Arif S.M. Lee E.A. Berkman G.D. Papasouliotis C. Li E.B. Stokes R. Hefti P. Moyer Veeco Instruments Turbodisc Operations 394 Elizabeth Avenue Somerset NJ 08873 U.S.A. Department of Electrical and Computer Engineering University of North Carolina at Charlotte 9201 University City Blvd Charlotte NC 28223 U.S.A. Center for Optoelectronics and Optical Communications University of North Carolina at Charlotte 9201 University City Blvd Charlotte NC 28223 U.S.A. Nanoscale Science Program University of North Carolina at Charlotte 9201 University City Blvd Charlotte NC 28223 U.S.A. Department of Physics & Optical Science University of North Carolina at Charlotte 9201 University City Blvd Charlotte NC 28223 U.S.A.

Blue light-emitting diodes (LED's), utilizing InGaN-based multi-quantum well (MQW) active regions deposited by organometallic chemical vapor epitaxy (OMVPE), are one of the fundamental building-blocks for current solid-state lighting applications. Studies [1,2] have previously been conducted to explore the optical and physical properties of the active MQW's over a variety of different OMVPE growth conditions. However, the conclusions of these papers have often been contradictory, possibly due to a limited data set or lack of understanding of the fundamental fluid dynamics and gas-phase chemistry that occurs during the deposition ***-quantum well structures grown over a range of pressures from typical low-pressure production processes at 200 Torr, up to near-atmospheric growth conditions at 700 Torr, have been investigated in this study. At all growth pressures, clear trends of gas-phase chemical reactions are observed for increased gas residence times (lower gas speeds from the injector flange and lower rotation rates) and increased V/III ratios (higher NH3 flows).Confocal microscopy, excitation-dependent PL (PLE), and time-resolved photo-luminescence (TRPL) have been employed on these MQW structures to investigate the carrier lifetime characteristics. Confocal emission images show spatially-separated bright and dark regions. The bright regions are red-shifted in wavelength relative to the dark regions, suggesting microscopic spatial localization of high indium content regions. As the growth pressure and gas residence times are reduced, a larger difference in band-gap between bright and dark regions, longer lifetimes, and higher average PL intensities can be obtained, indicating that higher optical quality material can be realized. Optimized MQW's grown at high pressure exhibit higher PLE slope intensities and IQE characteristics than lower pressure samples. Results on simple LED structures indicate that the improvement in MQW optical quality at high press

关键词： epitaxy metalorganic deposition optical properties

来源：评论

学校读者我要写书评

暂无评论

Multi-state Chiral Switching Through Adiabaticity Control in Encircling Exceptional Points

arXiv

引用

arXiv 2024年

作者： Li, Aodong Wang, Jian Alù, Andrea Chen, Lin Wuhan National Laboratory for Optoelectronics School of Optical and Electronic Information Huazhong University of Science and Technology Wuhan430074 China 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 Shenzhen Huazhong University of Science and Technology Research Institute Shenzhen518063 China School of Science and Engineering The Chinese University of Hong Kong Shenzhen518172 China

Dynamic encircling of exceptional points has attracted significant interest in recent years, as it can facilitate chiral transmission selectivity due to a nontrivial eigenstate evolution. Recently, multi-state systems have been explored, associated with more complex topologies supporting a larger number of exceptional points, but chiral switching among multiple eigenstates has remained elusive in experiments. Here, we overcome this challenge by dividing the eigenstate space into multiple subspaces by controlling the adiabaticity. The eigenstates in different subspaces can evolve without crosstalk, and chiral switching occurs as the eigenstates within each subspace are subject to a non-adiabatic transition while they encircle exceptional points. We experimentally demonstrate this phenomenon by reporting chiral switching for two groups of optical modes at telecom wavelengths in a four-state optical system, and theoretically demonstrate that our approach can be extended to higher-order systems. Our findings pave new avenues for studying chiral dynamics based on exceptional-point physics in multi-state systems, and offer opportunities to develop multiplexed photonic devices. © 2024, CC BY.

关键词： Photonic devices

来源：评论

学校读者我要写书评

暂无评论

optical Imaging of Flavor Order in Flat Band Graphene

arXiv

引用

arXiv 2024年

作者： Xie, Tian Wolf, Tobias M. Xu, Siyuan Cui, Zhiyuan Xiong, Richen Ou, Yunbo Hays, Patrick Holleis, Ludwig F. Guo, Yi Sheekey, Owen I. Patterson, Caitlin Arp, Trevor Watanabe, Kenji Taniguchi, Takashi Tongay, Seth Ariel Young, Andrea F. MacDonald, Allan H. Jin, Chenhao Department of Physics University of California at Santa Barbara Santa BarbaraCA93116 United States Department of Physics University of Texas at Austin AustinTX78712 United States Materials Science and Engineering Program School of Engineering for Matter Transport and Energy Arizona State University TempeAZ85287 United States Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan

Spin- and valley flavor polarization plays a central role in the many-body physics of flat band graphene1–21, with fermi surface reconstructions—often accompanied by quantized anomalous Hall1–8 and superconducting state9–14—observed in a variety of experimental systems. Here we describe an optical technique that sensitively and selectively detects flavor textures via the exciton response of a proximal transition metal dichalcogenide layer. Through a systematic study of rhombohedral and rotationally faulted graphene bilayers and trilayers, we show that when the semiconducting dichalcogenide is in direct contact with the graphene, the exciton response is most sensitive to the large momentum rearrangement of the Fermi surface, providing information that is distinct from and complementary to electrical compressibility measurements. The wide-field imaging capability of optical probes allows us to obtain spatial maps of flavor orders with high throughput, and with broad temperature and device compatibility. Our work paves the way for optical probing and imaging of flavor orders in flat band graphene systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Graphene

来源：评论

学校读者我要写书评

暂无评论

Full-color complex-amplitude vectorial holograms based on multi-freedom metasurfaces

arXiv

引用

arXiv 2019年

作者： Deng, Zi-Lan Jin, Mingke Ye, Xuan Wang, Shuai Shi, Tan Deng, Junhong Mao, Ningbin Cao, Yaoyu Guan, Bai-Ou Alù, Andrea Li, Guixin Li, Xiangping Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications Institute of Photonics Technology Jinan University Guangzhou510632 Department of Materials Science and Engineering Southern University of Science and Technology Shenzhen518055 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Photonics Initiative Advanced Science Research Center City University of New York 85 St. Nicholas Terrace New YorkNY10031 United States Physics Program Graduate Center City University of New York 365 Fifth Avenue New YorkNY10016 United States Department of Electrical Engineering City College of New York New YorkNY10031 United States

Phase, polarization, amplitude and frequency represent the basic dimensions of light, playing crucial roles for both fundamental light-mater interactions and all major optical applications. Metasurface emerges as a compact platform to manipulate these knobs, but previous metasurfaces have limited flexibility to simultaneous control them. Here, we introduce a multi-freedom metasurface that can simultaneously and independently modulate phase, polarization and amplitude in an analytical form, and further realize frequency multiplexing by a k-space engineering technique. The multi-freedom metasurface seamlessly combine geometric Pancharatnam-Berry phase and detour phase, both of which are frequency-independent. As a result, it allows complex-amplitude vectorial hologram at various frequencies based on the same design strategy, without sophisticated nanostructure searching of massive size parameters. Based on this principle, we experimentally demonstrate full-color complex-amplitude vectorial meta-holograms in the visible with a metal-insulator metal architecture, unlocking the long-sought full potential of advanced light field manipulation through ultrathin metasurfaces. Copyright © 2019, The Authors. All rights reserved.

关键词： Polarization

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：