检索结果-内蒙古大学图书馆

Higher-harmonic generation in boron-doped silicon from band carriers and bound-dopant photoionization

Physical Review Research 2023年第4期5卷 043141-043141页

作者： Fanqi Meng Frederik Walla Sergey Kovalev Jan-Christoph Deinert Igor Ilyakov Min Chen Alexey Ponomaryov Sergey G. Pavlov Heinz-Wilhelm Hübers Nikolay V. Abrosimov Christoph Jungemann Hartmut G. Roskos Mark D. Thomson Physikalisches Institut J. W. Goethe-Universität Max-von-Laue-Strasse 1 60438 Frankfurt am Main Germany Helmholtz-Zentrum Dresden-Rossendorf Bautzner Landstrasse 400 01328 Dresden Germany Institute of Optical Sensor Systems German Aerospace Center (DLR) 12489 Berlin Germany Institut für Physik Humboldt-Universität zu Berlin 12489 Berlin Germany Leibniz-Institut für Kristallzüchtung (IKZ) 12489 Berlin Germany Institut für Theoretische Elektrotechnik RWTH Aachen 52062 Aachen Germany

We investigate ultrafast harmonic generation (HG) in Si:B, driven by intense pump pulses with fields reaching ∼100kVcm−1 and a carrier frequency of 300 GHz, at 4 K and 300 K, both experimentally and theoretically. We report several findings concerning the nonlinear charge carrier dynamics in intense sub-THz fields: (i) Harmonics of order up to n=9 are observed at room temperature, while at low temperature we can resolve harmonics reaching at least n=11. The susceptibility per charge carrier at moderate field strength is as high as for charge carriers in graphene, considered to be one of the materials with the strongest sub-THz nonlinear response. (ii) For T=300 K, where the charge carriers bound to acceptors are fully thermally ionized into the valence subbands, the susceptibility values decrease with increasing field strength. Simulations incorporating multi-valence-band Monte Carlo and finite-difference-time-domain (FDTD) propagation show that here, the HG process becomes increasingly dominated by energy-dependent scattering rates over the contribution from band nonparabolicity, due to the onset of optical-phonon emission, which ultimately leads to the saturation at high fields. (iii) At T=4K, where the majority of charges are bound to acceptors, we observe a drastic rise of the HG yields for internal pump fields of ∼30kVcm−1, as one reaches the threshold for tunnel ionization. We disentangle the HG nonlinear response into contributions associated with the initial photoionization and subsequent motion in the bands, and show that intracycle scattering seriously degrades any contribution to HG emission from coherent recollision of the holes with their parent ions.

关键词： Carrier dynamics High-order harmonic generation Multiphoton or tunneling ionization & excitation Strong electromagnetic field effects Ultrafast phenomena finite-difference time-domain method Monte Carlo methods Terahertz spectroscopy

来源：评论

学校读者我要写书评

暂无评论

Research on the electromagnetic scattering from foam sea based on small slope approximation

引用

JOURNAL OF ENGINEERING-JOE 2021年第4期2021卷 226-233页

作者： Li, Xin-Hong Yichun Univ Coll Math & Comp Sci Yichun Peoples R China

In order to improve the research of electromagnetic scattering characteristics and mechanism of the foam in the marine environment, considering the complexity and sensitivity of the electromagnetic scattering characteristics of the sea surface, the electromagnetic scattering characteristics of the foam sea surface are studied by the improved small slope approximation (SSA) method. The double Debye dielectric constant model is adopted to calculate the dielectric constant of seawater and foam. Based on the Elfouhaily sea spectrum model, the expression of scattering coefficient of the foam sea surface under SSA is derived, and then the theoretical calculation results of the SSA method are compared with the finite-difference time-domain method and the measured values in the literature, which verifies the effectiveness of the proposed algorithm. The model of the relationship between the thickness of the foam layer and the wind speed is established, and the composite backscattering characteristics of the ocean below the wind speed of 20 m/s are simulated. It is found that as the wind speed increases, the foam layer becomes thicker and the scattering intensity increases. The foam layer will weaken the ocean specular reflection and increase the diffuse reflection, which is more obvious when viewed at grazing and large incidence angle, and when the incident angle is greater than 83 degrees, the inflexion point caused by the foam will be clearly observed in the backscattering curve. The results of this study can provide a reference for civil and military activities and optimise the detection capability in the marine environment.

关键词： Dielectric permittivity permittivity Instrumentation and techniques for geophysical, hydrospheric and lower atmosphere research scattering coefficient Other numerical methods ocean waves Numerical approximation and analysis slope approximation scattering intensity increases radiowave propagation velocity 20.0 m/s SSA method wind speed Radiowave propagation Surface waves, tides, and sea level foam layer finite difference time-domain analysis Winds and their effects in the lower atmosphere backscatter Elfouhaily sea spectrum model electromagnetic wave scattering marine environment wind rough surfaces composite backscattering characteristics Electromagnetic wave propagation foam sea surface finite-difference time-domain method seawater electromagnetic scattering characteristics

来源：评论

学校读者我要写书评

暂无评论

Inverse design of arbitrary optical helicity patterns

引用

Physical Review Research 2023年第3期5卷 033076-033076页

作者： Romuald Kilianski Robert Bennett School of Physics & Astronomy University of Glasgow Glasgow G12 8QQ United Kingdom

Superposing multiple plane waves can generate helicity lattices in which the optical helicity varies regularly in space. Here we propose an inverse design method for constructing arbitrary helicity structures based on placing a digital object consisting of dielectric inclusions in three-dimensional space. We apply the method to design structures that reproduce two-dimensional lattices embedded within a three-dimensional region using only a single plane wave as an input. In order to demonstrate the power and flexibility of our method, we go beyond the paradigm of a regular lattice and propose structures which can create arbitrary images consisting of regions of varying helicity, again using only a single plane wave as an input.

关键词： Optical lattices & traps Optimization problems finite-difference time-domain method

来源：评论

学校读者我要写书评

暂无评论

Mode Interference Effect in Optical Emission of Quantum Dots in Photonic Crystal Cavities

引用

Physical Review X 2022年第2期12卷 021042-021042页

作者： A. Lyasota C. Jarlov M. Nyman A. Miranda M. Calic B. Dwir A. Rudra A. Shevchenko E. Kapon Laboratory of Physics of Nanostructures Institute of Physics Ecole Polytechnique Federale de Lausanne (EPFL) CH-1015 Lausanne Switzerland Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of New South Wales Sydney New South Wales 2052 Australia Department of Applied Physics Aalto University P.O. Box 13500 FI-00076 Aalto Finland

Radiation properties of a pointlike source of light, such as a molecule or a semiconductor quantum dot, can be tailored by modifying its photonic environment. This phenomenon lies at the core of cavity quantum electrodynamics (CQED). Quantum dots in photonic crystal microcavities have served as a model system for exploring the CQED effects and for the realization of efficient single-photon quantum emitters. Recently, it has been suggested that quantum interference of the exciton recombination paths through the cavity and free-space modes can significantly modify the radiation. In this work, we report an unambiguous experimental observation of this fundamental effect in the emission spectra of site-controlled quantum dots positioned at prescribed locations within a photonic crystal cavity. The observed asymmetry in the polarization-resolved emission spectra strongly depends on the quantum dot position, which is confirmed by both analytical and numerical calculations. We perform quantum interferometry in the near-field zone of the radiation, retrieving the overlap and the position-dependent relative phase between the interfering free-space and cavity-mode-mediated radiative decays. The observed phenomenon is of importance for realization of photonic-crystal light emitters with near unity quantum efficiency. Our results suggest that the full description of light-matter interaction in the framework of CQED requires a modification of the conventional quantum master equation by also considering the radiation mode interference.

关键词： Cavity quantum electrodynamics Light-matter interaction Nanophotonics Open quantum systems Photonic crystals Photonics Quantum description of light-matter interaction Quantum interference effects Single photon sources Quantum cavities Quantum dots finite-difference time-domain method finite-element method Interferometry Optical spectroscopy Photoluminescence Quantum master equation time-resolved photoluminescence

来源：评论

学校读者我要写书评

暂无评论

finite-difference time-domain scheme for nonlinear acoustic waves in solids

引用

MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2019年第0期130卷 790-799页

作者： Wang, Xiaoyu Gong, Xun Qin, Chuanxi Zhang, De Wu, Haodong Zhang, Dong Nanjing Univ Key Lab Modern Acoust Dept Acoust Sci & Enginee Coll PhysMinist EducInst Acoust 22 Hankou Rd Nanjing 210093 Jiangsu Peoples R China

A general finite-difference time-domain (FDTD) method for numerical simulation of the nonlinear acoustic wave in conservative (nondissipative) solids is presented. We apply the spatial derivatives of displacements instead of stress and particle velocity as the bases to discretize the governing partial differential equations. The mathematical model is completely compatible with its linear counterpart. The model solution keeps stable even very near to the formation of a shock wave. As numerical examples, the FDTD scheme is used to investigate the longitudinal and transverse plane waves in infinite isotropic material. In the case of longitudinal wave, a sinusoidal wave transforms into a wave with a sawtooth profile eventually. The distance for the formation of a discontinuity can be obtained directly. The primary and the high order harmonic waves vary with the travelling distance in a very complex way. In the case of transverse wave, high order transverse waves are neglectable and high order longitudinal waves are generated instead. This method dose not need linearization of the governing equations. It can also be used to deal with nonlinear acoustic wave in anisotropic solids without modification. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Nonlinear acoustic waves in solids finite-difference time-domain method Perturbation theory

来源：评论

学校读者我要写书评

暂无评论

Interaction between microwave and dielectric surface discharge in vacuum and low-pressure gas

引用

PLASMA SOURCES SCIENCE & TECHNOLOGY 2022年第9期31卷 095005-095005页

作者： Zhao, Pengcheng Wang, Rui Guo, Lixin Xidian Univ Sch Phys Xian 710071 Peoples R China China Acad Space Technol Natl Key Lab Sci & Technol Space Microwave Xian 710100 Peoples R China

The interaction between high-power microwave and dielectric surface discharge in vacuum and low-pressure gas is investigated by using an electromagnetic particle-in-cell-Monte Carlo collision model. Maxwell equations are solved by the finite-difference time-domain method combined with the boundary condition between the total and scattered field. The simulation results show that the transmission power loss is small and mainly attributed to the absorption of surface discharge, when the secondary electron multipactor reaches a steady state in vacuum. The simulated value of transmission power loss in vacuum is in good agreement with the experimental data. At a low pressure, the multipactor is the main source of electrons in the initial stage of discharge. After the multipactor reaches a steady state, the ionization leads to a significant increase in the number density of plasma near the dielectric surface. The absorbed power of plasma is greater than the reflected power in the initial stage of discharge, but with the increase of time, the latter becomes larger and even close to the power of incident wave. As the pressure increases, the transmission power decays faster due to the increase of ionization rate. When the microwave field near the dielectric surface decays significantly at a low pressure, the steady state of multipactor disappears, and the peak of plasma number density is near the surface, but not closest to the surface.

关键词： secondary electron multipactor collisional ionization dielectric surface discharge particle-in-cell-Monte Carlo collision model finite-difference time-domain method high-power microwave

来源：评论

学校读者我要写书评

暂无评论

Optical Performance of CMOS Image Sensor Pixels: Simulation Study

Optical Performance of CMOS Image Sensor Pixels: Simulation ...

引用

International Symposium of the Applied-Computational-Electromagnetics-Society (ACES)

作者： Banejiee, Saswatee Sawai, Yusuke Chen, Anny Miyauchi, Ken Han, Sangman BRILLNICS Japan Inc Tokyo Japan

ISBN: (纸本)9781733509626

CMOS image sensor (CIS) pixels are formed by stacking multiple layers of semiconductor materials. Currently, industrial development of such photonic devices includes a design step where light propagation is simulated using numerical methods such as, finite-difference time-domain (FDTD). We discuss the FDTD simulation of CIS pixels to predict the optical properties as function of wavelength and incident angle.

关键词： CMOS Image Sensors silicon photonics subwavelength optics design and simulation finite-difference time-domain method refractive indices of materials thin films

来源：评论

学校读者我要写书评

暂无评论

Realization of topological superlattices and the associated interface states in one-dimensional plasmonic crystals

引用

Physical Review B 2022年第4期106卷 045401-045401页

作者： C. Liu H. C. Ong Department of Physics The Chinese University of Hong Kong Shatin Hong Kong

In analogy to the Su-Schrieffer-Heeger (SSH) model, one-dimensional (1D) electromagnetic (EM) crystals can exhibit nontrivial topological properties. When a nontrivial EM crystal is in contact with its trivial counterpart, a topologically protected interface state is formed. While much attention has been focused on a single interface state, multiple interface states can interact collectively when suitable conditions are met, giving rise to nontrivial band topologies resembling the standard SSH model. Here, we study the topological properties of 1D metallic superlattices that support multiple interface states. We first demonstrate that a single interface state exists at the boundary between two topologically distinct metallic arrays that carry Bloch-like surface plasmon polaritons. Such an interface state is then used as the building block for further constructing the superlattices. By exploiting the separation between two dimerized interface states and the distinct inter- and intrainterface configurations to facilitate different intracell and intercell interactions, we vary the band topology of the superlattices. More importantly, a new superlattice interface state is formed when trivial and nontrivial superlattices are brought together. The superlattice interface state is found to have smaller angular divergence and longer localization length than its single counterpart, thus is desired for robust signal transmission and a high finesse cavity.

关键词： Plasmonics Topological effects in photonic systems Superlattices finite-difference time-domain method Reflectivity

来源：评论

学校读者我要写书评

暂无评论

Surface-Emitting Broadband THz Quantum Cascade Laser Frequency Combs with Inverse-Designed Waveguide Facets

Surface-Emitting Broadband THz Quantum Cascade Laser Frequen...

引用

Conference on Lasers and Electro-Optics Europe (CLEO EUROPE)

作者： Sebastian Gloor Urban Senica Paolo Micheletti Mattias Beck Jérôme Faist Giacomo Scalari Institute of Quantum Electronics ETH Zürich Zürich Switzerland

ISBN: (纸本)9798350345995

THz Quantum Cascade Lasers are unipolar electrically driven semiconductor lasers that can also operate as frequency combs for broadband metrology and sensing [1], [2]. THz quantum cascade lasers are usually processed in double metal waveguide ridges exhibiting low slope efficiencies and a patterned far field [3]. Surrounding the ridge structure with the low-loss polymer Benzocyclobuten (BCB) allows for an extended top contact improving waveguide and thermal properties as well as permitting the implementation of passive structures [4].

关键词： finite-difference time-domain method Frequency combs Laser coupling Laser operation Lasers Semiconductor lasers

来源：评论

学校读者我要写书评

暂无评论

Recent techniques on sound field simulation

引用

JAPANESE JOURNAL OF APPLIED PHYSICS 2022年第SG期61卷 SG0801-SG0801页

作者： Tsuchiya, Takao Doshisha Univ Dept Informat Syst Design Kyoto 6100321 Japan

This is a tutorial paper on the basics and applications of the finite-difference time-domain (FDTD) method. Two types of discretization of the linear governing equations, the scalar-type FDTD method and the vector-type one, are first discussed. Then the basic concept of the compact explicit-FDTD (CE-FDTD) method is described. By considering the relationship between the cutoff frequency and the computer resources, it is shown that the interpolated wide band scheme requires the least computer resources among the derivative schemes of the CE-FDTD method. The discretization of the arbitrary shaped sound field by voxels and its boundary conditions, and the implementation of the density variation are also described. The sound field rendering and its real time renderer "Silicon concert hall" are introduced.

关键词： finite-difference time-domain method compact explicit FDTD method sound field rendering Silicon concert hall SUF2VOX voxelizer

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：