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受衍射极限的限制,传统太赫兹成像分辨率在毫米量级,无法满足目前前沿研究向微纳米尺度发展的主要趋势。高时空分辨率太赫兹成像技术成为当下太赫兹领域最重要的研究热点之一。近场太赫兹成像技术是实验中将太赫兹成像分辨率提升至微纳米量级的重要方法。介绍了近场太赫兹成像技术的基本原理,详述了多种近场太赫兹成像技术的发展历程与技术路线,从时空分辨能力、频谱分辨能力、成像质量、成像信噪比和适用场景等多个角度分析并总结了各种近场太赫兹成像技术的优势和不足。最后,讨论并展望了太赫兹超分辨成像未来的发展趋势。 相似文献
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用平面波展开法研究了太赫兹(THz)波在二维三角晶格光子晶体中的传输特性。数值计算了以硅为背景的空气圆柱构成的二维三角晶格光子晶体的能带结构和态密度,计算表明在介质圆柱半径r=0.47a(a为空气介质柱的晶格常数)出现最大完全光子带隙,带隙宽度为0.070 1 THz;当r=0.49a和r=0.45a时,E偏振和H偏振分别出现最大光子带隙,带隙宽度分别0.102 2,0.192 3 THz。光子晶体能态密度的分布也表明了存在光子带隙的范围。研究结果为THz器件的开发提供了理论依据。 相似文献
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根据Drude模型在理论上计算了太赫兹(THz)波段二维黑磷(2D BP)在扶手椅方向(X)和锯齿方向(Y)上电导率随频率的色散及吸收.发现2D BP在X和Y两个方向上电导率不同,从而导致了其介电常数的不同,进而可以对不同偏振方向的THz波起到不同的调制作用.利用2D BP对THz波具有偏振依赖的特性,设计了2D BP-SiO2三明治周期结构,通过三维电磁场仿真软件CST Microwave Studio计算了这种结构对THz波的调控特性,研究发现,这种结构对不同偏振方向入射的THz波有不同的吸收;改变结构中底层SiO2层的厚度,结构的吸收率也发生了相应的变化.基于此,研究提出了这种结构对偏振平行于2D BP扶手椅方向和锯齿方向的THz脉冲有最大吸收率差时的底层SiO2层厚度.结果表明这种结构可以用于设计新型结构紧凑的THz吸收器和偏振器. 相似文献
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利用超材料吸波体对材料参数的电磁响应, 可将其应用于传感. 本文设计了一种工字形单元结构的超材料吸波体, 基于频域算法对其在太赫兹频段的传感特性进行数值模拟, 研究了待测样品折射率、厚度及电介质隔层厚度对超材料吸波体传感器的频率灵敏度、振幅灵敏度及品质因数的影响. 研究结果表明:当待测样品厚度为40 μm时, 折射率频率灵敏度可达到153.17 GHz/RIU, 折射率振幅灵敏度可达到41.37%/RIU; 待测样品折射率一定时, 厚度频率灵敏度随其厚度的增大而线性减小; 随着待测样品厚度的增加, RFOM呈增大趋势, 但增大幅度在逐渐减小; TFOM随待测样品厚度的增加而减小. 相似文献
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太赫兹科学技术在光谱、成像、传感、生物医药、安全检测等方面展现出了巨大的应用潜力和价值。基于新材料和新机理,研发高效、超宽带和低成本的太赫兹光子学器件是太赫兹科学技术的重要挑战。近年来的研究表明,太赫兹光子学和超快自旋电子学深度交叉,获得了很大的关注。本文对超快太赫兹自旋光电子学所研究的物理机理和器件设计应用进行讨论。在物理机理研究方面,阐明了太赫兹脉冲为研究超快自旋电子学提供强大工具,实现了太赫兹驱动自旋波,探测自旋输运和超快磁测量。在器件设计与应用方面,介绍了基于自旋的新型太赫兹光子学器件,包括自旋太赫兹辐射源的优化方法,自旋太赫兹调制器的工作原理,自旋太赫兹探测器的设计方案。超快太赫兹自旋光电子学不仅有助于人们理解宏观自旋电子学现象背后的微观物理机制,而且有望实现高效的太赫兹光子学器件和光谱学应用。 相似文献
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为实现高效太赫兹调控,迫切需要一种高效且成本低的材料。新型钙钛矿材料由于其优异的光电特性,加上钙钛矿制备工艺简单、可大批量生产等优点,非常适合作为太赫兹超材料的活性材料,通过外部激励改变活性材料的属性,可灵活调控太赫兹波。因此,选择新型钙钛矿材料外加光场调控太赫兹,分析在光场作用前(绝缘态)和在光场作用后(金属态)两种状态对单元结构太赫兹宽波段下幅值和相位的影响。设计出光场灵活调控的钙钛矿基1 bit太赫兹编码超表面结构,该结构由有机无机杂化钙钛CH3NH3PbI3(MAPbI3)、聚酰亚胺和铝构成。通过CST仿真结果显示,该超表面结构在光场的调控下能够实现宽谱(0.1、1、2、6 THz)太赫兹波的180°相位差变化,经过超表面编码结构的设计,同一编码序列实现远场波束的变换。研究结果表明,基于光场操控钙钛矿材料的编码超表面为实现灵活的太赫兹波调控提供了新的思路,在太赫兹通信、安检、生物医学成像等方面具有巨大的应用潜力。 相似文献
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A theoretical study of harmonic generation in a short period AlGaN/GaN superlattice induced by a terahertz field 下载免费PDF全文
Based on an improved energy dispersion relation, the
terahertz field induced nonlinear transport of miniband electrons in
a short period AlGaN/GaN superlattice is theoretically studied in
this paper with a semiclassical theory. To a short period
superlattice, it is not precise enough to calculate the energy
dispersion relation by just using the nearest wells in tight binding
method: the next to nearest wells should be considered. The results
show that the electron drift velocity is 30% lower under a dc
field but 10% higher under an ac field than the traditional
simple cosine model obtained from the tight binding method. The
influence of the terahertz field strength and frequency on the
harmonic amplitude, phase and power efficiency is calculated. The
relative power efficiency of the third harmonic reaches the peak
value when the dc field strength equals about three times the
critical field strength and the ac field strength equals about four
times the critical field strength. These results show that the
AlGaN/GaN superlattice is a promising candidate to convert radiation
of frequency ω to radiation of frequency 3ω or even
higher. 相似文献
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X.L. Lei H.L. Cui 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(4):513-518
We suggest a balance-equation approach to hot-electron transport in a single arbitrary energy band subject to an intense radiation
field of terahertz (THz) frequency, including all the multiphoton emission and absorption processes and taking account of
realistic scatterings due to impurities and phonons. This approach, which allows one to calculate THz-driving, time-averaging
transport based on a set of time-independent equations, provides a convenient method to study the effect of an intense THz
electric field on carrier transport in a nonparabolic energy band. As an example, these fully three-dimensional, acceleration-
and energy-balance equations are applied to the discussion of superlattice miniband transport at lattice temperature T=77 and 300 K driven by the THz radiation field of varying strengths. It is shown that the current through a dc biased miniband
superlattice is greatly reduced by the irradiation of an intense THz electric field.
Received: 23 January 1998 / Revised: 31 March 1998 / Accepted: 20 April 1998 相似文献
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Effect of magnetic field on the terahertz radiationdetection in high electron mobility transistors 下载免费PDF全文
In this paper, we make a theoretical investigation of the
plasma-wave instability mechanism in a two-dimensional electron
fluid in a high electron mobility transistor (HEMT) driven by the
terahertz radiation in the presence of a perpendicular magnetic
field. It is found that the resonant peaks of the
gate-to-source/drain admittances and detection responsivity depend
on the strength of the external magnetic field. Such phenomena can
be used to produce a desired effect by adjusting the intensity of
the magnetic field. 相似文献
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We investigate the shot noise properties in a monolayer graphene superlattice modulated by N parallel ferromagnets deposited on a dielectric layer. It is found that for the antiparallel magnetization configuration or when magnetic field is zero the new Dirac-like point appears in graphene superlattice. The transport is almost forbidden at this new Dirac-like point, and the Fano factor reaches its maximum value 1/3. In the parallel magnetization configuration as the number of magnetic barriers increases, the shot noise increases. In this case, the transmission can be blocked by the magnetic–electric barrier and the Fano factor approaches 1, which is dramatically distinguishable from that in antiparallel alignment. The results may be helpful to control the electron transport in graphene-based electronic devices. 相似文献
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研究了基于硅烯的静电势超晶格、铁磁超晶格、反铁磁超晶格中谷极化、自旋极化以及赝自旋极化的输运性质,分析了铁磁交换场、反铁磁交换场以及化学势对输运性质的影响,讨论了电场对谷极化、自旋极化以及赝自旋极化的调控作用.结果表明:当3种超晶格的晶格数达到10以上时,在硅烯超晶格中很容易实现100%的谷极化、自旋极化和赝自旋极化,而且通过调节超晶格上的外加电场可以使极化方向发生翻转,从而在硅烯超晶格中实现外电场对谷自由度、自旋自由度以及赝自旋自由度的操控. 相似文献
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Dynamics of a pair of electron and hole in semiconductor superlattice under an intense electric field 下载免费PDF全文
This paper investigates the behavior of a pair of electron and hole
in semiconductor superlattice under an external electric field with
the consideration of Coulomb interaction. By numerically calculating
the corresponding probability in the nearest neighbor tight binding
approximation, we find that the single electron (or the hole) can
not be dynamically localized due to the Coulomb interaction, while
the dynamic localization of exciton (the pair of the electron and
hole) still exists. Moreover we find that with the increase of the
intensity of electric field, the exciton can be dynamically
localized more completely. 相似文献
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双阱光学超晶格中的超冷原子是近期冷原子物理领域的研究热点. 本文推广提出了实现三阱光学超晶格的方案, 并采用精确对角化的方法分别研究了弱磁场下对称三阱 光学超晶格中铁磁性和反铁磁性的自旋为1的原子系统的基态, 发现二者的相图很不相同: 反铁磁性原子对应的相图中没有沿磁场方向总自旋磁量子数为±2的基态, 而铁磁性原子对应的相图中可能有. 在负的二次塞曼能量区域, 铁磁性原子的相图中只有完全极化态. 分析了可控参数影响基态的物理本质. 由于这些量子自旋态可以通过调节外磁场和光势垒的高度非常简便而精确地控制, 适合用来研究自旋纠缠.
关键词:
三阱光学超晶格
自旋为1的原子
弱磁场 相似文献
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Optical absorption and electromagnetically induced transparency in semiconductor quantum well driven by intense terahertz field 下载免费PDF全文
An approach for solving the excitonic absorption in a semiconductor quantum well driven by an intense terahertz field is presented.The formalism relies on the stationary single-photon Schro¨dinger equation in the full quantum mechanical framework.The optical absorption dynamics in both weak and strong couplings are discussed and compared.The excitonic absorption spectra show the Autler-Townes doublets for the resonance terahertz field,a replica peak for the non-resonance terahertz field,and the electromagnetically induced transparency phenomenon for modulating the decay rate of the second electron state in the weak coupling.In particular,the electromagnetically induced transparency phenomenon window range is discussed.In the strong coupling region,the multi-order energy level resonance splitting due to the strong optical field is found.There are three(non-resonance terahertz field) or four(resonance terahertz field) peaks in the optical absorption spectra.This work provides a simple and convenient approach to deal with the optical absorption in the exciton system. 相似文献
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Electron transport across a quantum wire embedding a saw-tooth superlattice 总被引:1,自引:0,他引:1 下载免费PDF全文
By developing the recursive Green function method, the transport properties through a quantum wire embedding a finite-length saw-tooth superlattice are studied in the presence of magnetic field. The effects of magnetic modulation and the geometric structures of the superlattice on transmission coefficient are discussed. It is shown that resonant peak splitting of this kind of structure is different from that of ‘magnetic' and ‘electric' superlattices in two-dimensional electron gas. The transmission spectrum can be tailored to match requirements through adjusting the size of saw-tooth quantum dot and field strength. 相似文献