检索结果-内蒙古大学图书馆

arXiv 2018年

作者： Chen, Q. Zhang, L. He, M. Gao, F. Chen, H. Chen, Q. Zhang, L. He, M. Gao, F. Chen, H. Wang, Z. Lin, X. Yang, Y. Zhang, B. Yang, Y. Zhang, B. State Key Laboratory of Modern Optical Instrumentation College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Electromagnetics Academy at Zhejiang University Zhejiang University Hangzhou310027 China School of Information Science and Engineering Shandong University Jinan250100 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore637371 Singapore Centre for Disruptive Photonic Technologies Photonics Institute Nanyang Technological University 50 Nanyang Avenue Singapore639798 Singapore

Extensive researches have revealed that valley, a binary degree of freedom (DOF), can be an excellent candidate of information carrier. Recently, valley DOF has been introduced into photonic systems, and several valley-Hall photonic topological insulators (PTIs) have been experimentally demonstrated. However, in the previous valley-Hall PTIs, topological kink states only work at a single frequency band, which limits potential applications in multiband waveguides, filters, communications, and so on. To overcome this challenge, here we experimentally demonstrate a valley-Hall PTI, where the topological kink states exist at two separated frequency bands, in a microwave substrate-integrated circuitry. Both the simulated and experimental results demonstrate the dual-band valley-Hall topological kink states are robust against the sharp bends of the internal domain wall with negligible inter-valley scattering. Our work may pave the way for multi-channel substrate-integrated photonic devices with high efficiency and high capacity for information communications and processing. Copyright © 2018, The Authors. All rights reserved.

关键词： Electric insulators

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Type-I hyperbolic metasurfaces for highly-squeezed designer polaritons with negative group velocity

arXiv

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arXiv 2018年

作者： Yang, Yihao Qin, Pengfei Lin, Xiao Li, Erping Wang, Zuojia Zhang, Baile Chen, Hongsheng State Key Laboratory of Modern Optical Instrumentation College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Electromagnetics Academy at Zhejiang University Zhejiang University Hangzhou310027 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore637371 Singapore Centre for Disruptive Photonic Technologies Photonics Institute Nanyang Technological University 50 Nanyang Avenue Singapore639798 Singapore School of Information Science and Engineering Shandong University Qingdao266237 China

Hyperbolic polaritons in van der Waals materials and metamaterial heterostructures provide unprecedenced control over light-matter interaction at the extreme nanoscale. Here, we propose a concept of type-I hyperbolic metasurface supporting highly-squeezed magnetic designer polaritons, which act as magnetic analogues to hyperbolic polaritons in the hexagonal boron nitride (h-BN) in the first Reststrahlen band. Comparing with the natural h-BN, the size and spacing of the metasurface unit cell can be readily scaled up (or down), allowing for manipulating designer polaritons in frequency and in space at will. Experimental measurements display the cone-like hyperbolic dispersion in the momentum space, associating with an effective refractive index up to 60 and a group velocity down to 1/400 of the light speed in vacuum. By tailoring the proposed metasurface, we experimentally demonstrate an ultra-compact (with a footprint shrunken by 3600 times) integrated designer polariton circuit including high-transmission 90° sharp bending waveguides and waveguide splitters. The designed metasurface with a low profile, lightweight, and ease of access, can serve as an alternatively promising platform for emerging polaritonics, and may find many other potential applications, such as waveguiding, sensing, subdiffraction focusing/imaging, low-threshold Cherenkov radiation, strong magnetic transition enhancement, wireless energy transfer, and so forth. Copyright © 2018, The Authors. All rights reserved.

关键词： Phonons

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Graphene based functional devices: A short review

arXiv

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arXiv 2018年

作者： Wang, Rong Jiang, Lijun Ren, Xingang Yan, Ze Sha, Wei E.I. Shan, Guangcun Department of Electrical and Electronic Engineering University of Hong Kong Pokfulam Road Hong Kong Key Laboratory of Intelligent Computing & Signal Processing Ministry of Education Anhui University Hefei230039 China School of Instrumentation Science & Opto-electronics Engineering Beihang University Beijing100191 China Key Laboratory of Micro-nano Electronic Devices and Smart Systems of Zhejiang Province College of Information Science & Electronic Engineering Zhejiang University Hangzhou310027 China School of Instrumentation Science & Opto-electronics Engineering Beihang University Beijing100191 China California NanoSystem Institute Department of Chemistry & Biochemistry University of California Los AngelesCA90095 United States

Graphene is an ideal 2D material system bridging electronic and photonic devices. It also breaks the fundamental speed and size limits by electronics and photonics, respectively. Graphene offers multiple functions of signal transmission, emission, modulation, and detection in a broad band, high speed, compact size, and low loss. Here, we will have a brief view of graphene based functional devices at microwave, terahertz, and optical frequencies. Their fundamental physics and computational models will be discussed as well. Copyright © 2018, The Authors. All rights reserved.

关键词： Graphene

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Multifrequency superscattering from subwavelength hyperbolic structures

arXiv

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arXiv 2018年

作者： Qian, Chao Lin, Xiao Yang, Yi Gao, Fei Shen, Yichen Lopez, Josue Kaminer, Ido Zhang, Baile Li, Erping Soljačić, Marin Chen, Hongsheng Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Electromagnetics Academy at Zhejiang University Zhejiang University Hangzhou310027 China ZJU-UIUC Institute College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore637371 Singapore Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Centre for Disruptive Photonic Technologies NTU Singapore637371 Singapore

Superscattering, i.e., a phenomenon of the scattering cross section from a subwavelength object exceeding the single-channel limit, has important prospects in enhanced sensing/spectroscopy, solar cells, and biomedical imaging. Superscattering can be typically constructed only at a single frequency regime, and depends critically on the inescapable material losses. Under such realistic conditions, superscattering has not been predicted nor observed to exist simultaneously at multiple frequency regimes. Here we introduce multifrequency superscattering in a subwavelength hyperbolic structure, which can be made from artificial metamaterials or from naturally-existing materials, such as hexagonal boron nitride (BN), and show the advantage of such hyperbolic materials for reducing structural complexity. The underlying mechanism is revealed to be the multimode resonances at multiple frequency regimes as appear in BN due to the peculiar dispersion of phonon-polaritons. Importantly, the multifrequency superscattering has a high tolerance to material losses and some structural variations, bringing the concept of multifrequency superscattering closer to useful and realistic conditions. Copyright © 2018, The Authors. All rights reserved.

关键词： III-V semiconductors

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Dissipative quantum electromagnetics

arXiv

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arXiv 2017年

作者： Wei, E.I.Sha Aiyin, Y.Liu Chew, Weng Cho Key Laboratory of Micro-nano Electronic Devices and Smart Systems of Zhejiang Province College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign ChampaignIL61801 United States Department of Electrical and Computer Engineering Purdue University West LafayetteIN47907 United States

The dissipative quantum electromagnetics is introduced in a comprehensive manner as a field-matter-bath coupling problem. First, the matter is described by a cluster of Lorentz oscillators. Then the Maxwellian free field is coupled to the Lorentz oscillators to describe a frequency dispersive medium. The classical Hamiltonian is derived for such a coupled system, using Lorenz gauge and decoupled scalar and vector potential formulations. The classical equations of motion are derivable from the Hamiltonian using Hamilton equations. Then the Hamiltonian is quantized with all the pertinent variables with the introduction of commutators between the variables and their conjugate pairs. The quantum equations of motion can be derived using the quantum Hamilton equations. It can be shown that such a quantization scheme preserves the quantum commutators introduced. Then a noise bath consisting of simple harmonic oscillators is introduced and coupled to the matter consisting of Lorentz oscillators to induce quantum loss. Langevin source emerges naturally in such a procedure, and it can be shown that the results are consistent with the fluctuation dissipation theorem, and the quantization procedure of Welsch's group. The advantage of the present procedure is that no diagonalization of the Hamiltonian is necessary to arrive at the quantum equations of motion. Finally, we apply the quantization scheme to model spontaneous emission of a two-level polarized atom placed above a dielectric cylinder that supports a bound state in the continuum. Copyright © 2017, The Authors. All rights reserved.

关键词： Hamiltonians

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