光频段双层手征结构光学特性及负折射率研究

设计了一种工作在光波段的新型四重对称的双层手征结构,通过数值模拟得到透射系数和反射系数,反演计算了结构的圆二色性、旋光角、手征参数和折射率。结果表明该结构在谐振波长附近具有很强的旋光性,并且在椭偏度为零时,即透射光变成完全线偏振光时,旋光角达到了55°;在一定波段内可以实现左旋圆偏振光(LCP)和右旋圆偏振光(RCP)的负折射率,且不需要介电常数和磁导率同时为负,更重要的是,实现负折射率的左旋圆偏振光(LCP)具有较宽的频带,不局限于谐振波长附近,在椭偏度为零时,折射率也为负。考虑到具体的实验制作,对加衬底的手征结构进行了数值模拟,结果表明谐振波长向长波长方向产生了偏移,完全线性偏振光的旋光角仍然有40°。     

太赫兹波段双频带手征性超表面的设计

提出一种具有巨旋光性和负折射特性的双频带手征性超表面结构,该手征性超表面由中间介质层和双层共轭卍字形周期排列而成;通过研究面电流密度分布,解释了巨旋光性和负折射率产生的原因;研究了手征性超表面单元结构的连续圆金属贴片半径和介质层厚度对该结构旋光性和负折射特性的影响。数值模拟结果表明:该结构在0.1～2 THz频率范围内有4个谐振频点,在谐振频点附近,平均折射率均为负值,实部幅值最大为-3.7;该结构在谐振频点附近显示了巨旋光性以及双频带的左旋圆偏振波和右旋圆偏振波负折射特性,最大偏振旋转角达到了122°,右旋圆偏振波折射率实部幅值可达-12.74。     

基于折线形手征负折射介质结构的设计与仿真

分别设计和仿真了一种新型的工作在微波段和光波段的折线形手征介质结构.利用仿真得到的透射系数和反射系数反演计算了该结构的旋光角、椭偏度、相对介电常数、相对磁导率、手征参数以及折射率等参数.结果表明该结构在这两种波段下都显示出极大的旋光角和椭偏度,且因具有大的手征参数,而不再需要介电常数和磁导率同时为负就可实现左旋圆极化波(LCP)和右旋圆极化波(RCP)的负折射率. 关键词： 手征介质 旋光角 椭偏度 负折射率     

光轴平行于界面的单轴手征介质中的负折射研究

研究了光轴平行于界面时单轴各向异性手征介质中实现负折射的条件, 并详细分析了该介质中两个本征波在不同电磁参数和手征参数下折射角随入射角的变化规律. 结果表明, 利用单轴各向异性手征介质实现负折射, 条件更加宽松, 甚至在弱的手征参数下也可能实现负折射, 且在不同的介电常数、手征参数和入射角下, 该手征介质中两个本征波的相折射角存在很大的差异, 在特殊条件下, 某一个或两个本征波不能在介质内传播.     

填充多层互易手征介质金属同轴线传播特性

 采用在圆柱坐标系中分离变量的方法，推出填充多层互易手征介质的金属同轴线各层电磁场之间的关系，得到其模式特征方程和圆波导模式特征方程，给出了填充两层手征介质金属同轴线部分模式的色散特性的数值计算结果，分析了手征介质参量及两层手征介质厚度变化等对手征同轴线传播特性的影响。如果互易手征介质的手征参数等于零，可得填充普通介质的同轴线的模式特征方程。与填充普通介质的同轴线中的模式相比，手征同轴线中的模式发生了分叉。当同轴线中所填介质的折射率增大时，其模式归一化截止频率和进行基模单模传输的带宽归一化频率都将减小。     

线偏振光在手征负折射材料表面的传输特性研究

从理论上研究了手征负折射材料表面的反射与透射特性,给出了归一化的反射透射功率与入射角之间的关系曲线.当入射波分别为垂直和平行极化波(TE和TM波)时,得到了发生负折射时的布儒斯特角和全内反射角随手征参数和材料折射率的变化关系.手征负折射介质中的一个本征波发生了负折射,其功率流方向与波矢方向相反.     

负折射率介质测试装置设计与测试

为深人了解负折射率媒质的奇异传输特性,基于斯涅耳折射原理,设计并加工了一种用于测试X波段((8.2-12.4GHz),以亚铁磁材料为基体,内嵌金属线阵列宏结构的负折射率介质样品折射特性的实验装置.分别测试了楔形石蜡样品和楔形负折射率介质样品在波段的折射特性,对石蜡样品测试结果的分析证明了该折射特性测试装置的有效性,对负...     

单模手征光纤研究

对圆芯和内外包层都为手征介质构成的双包层手征光纤（W型）进行了解求解,导出了模式场解及模式特征方程,然后用数值计算的方法研究了手征参数对模式的色散曲线和截止频率的影响,结果发现在双包层光纤的纤芯中引入手征或在单包层光纤的包层中引入手征,都可以实现单模工作。     

单轴各向异性手征介质平板的反射和透射特性研究

研究了光轴平行于界面的单轴各向异性手征介质平板对平面电磁波的反射和透射特性, 推导出了反射和透射系数(功率)公式; 按介电常数的正负分4种情形给出了反射和透射功率曲线; 讨论了手征参数对反射和透射特性的影响, 特别是给出了伪布儒斯特角与手征参数的变化关系曲线. 关键词： 单轴各向异性手征介质 手征参数 伪布儒斯特角 反射和透射     

手征参数对光纤中模式特性的影响

对圆芯和包层都是手征介质的阶跃型手征光纤进行了解析求解，导出了模式特征方程，给出了手征光纤中模式场，光强和光功率分布的表达式。分别研究了纤芯和包层中的手征参数对模式特性的影响．。     

The negative electromagnetic attractive forces arising from kinetic energy of conduction electrons in double-layer metallic nanowire arrays

The coupled-nanowire plasmatic resonances and very strong negative electromagnetic force between the double-layer metallic nanowire arrays is investigated theoretically. The negative electromagnetic force indicates attractive interaction between the metallic nanowires with the air-gap cavity local resonance effect. Plasmon resonances lead to extremely large localized ?eld, thereby resulting in large mutual coupling forces between the double-layer metallic nanowire arrays. The light coupling into metallic microcavity can stimulate collective electron oscillations of plasmatic resonance, and cause the contraction of the negative pressure in metallic cavity wall. The electromagnetic field of the plasmatic resonance mode is mainly localized inside the air-gap region between the two wires.     

Chiral organic glass and its infrared spectrum property

Chiral molecules griseofulvin were disseminated homogeneously in poly methyl metahcrylate (PMMA) host, which agglomerate from methyl metahcrylate and N, N-dimethyl formamide dimethyl acetal, using benzoyl peroxide as a catalyst. So the chiral organic glass has been manufactured successfully. Its optical rotatory were investigated from a solution state to a solid state. The results of measurement show that the chiral parameter of the chiral organic glass is 2.65×10^{-7} and its specific rotation has increased compared with its solution condition. Its infrared spectra property has been measured by Fourier transformation infrared spectrometer. The results show that the chiral molecules fill in the pore of the network structure in the organic glass, which hardly link with the host.     

Enhanced and tunable circular dichroism in the visible waveband by coupling of the waveguide mode and local surface plasmon resonances in double-layer asymmetric metal grating

Circular dichroism (CD) has shown very interesting possibilities as a means to characterize the chiral signal of a chiral structure. Here, we theoretically demonstrated enhanced and tunable CD in the visible light regime using a composite structure consisting of a double-layer metal grating gaped by a dielectric waveguide layer. Based on the coupling of the waveguide modes and the localized plasmonic resonances, the CD could reach a maximum value as high as 0.52 at 635 nm, which is four times higher than the CD value obtained in a conventional double-layer grating without the waveguide coupling effect. Furthermore, the spectral positions of the enhanced CD bands could be easily tuned by controlling the structural parameters. The proposed hybrid double-grating and waveguide structures could have potential applications in chiral selective imaging, sensing and spectroscopy, especially where the transmission measurement is required.     

Tunable Polycyclic Chiral Beams

The generation of polycyclic chiral beams by inducing annular spiral zone phases that consist of multiple subphases is numerically and experimentally demonstrated. Each subphase is composed of a spiral phase, an equiphase, and a radial phase. The number and twisting direction of the spiral intensity lobes for every layer could be individually controlled. Furthermore, the orientations for the twisting lobes could be tuned by changing the introduced equiphase gradient. More importantly, such optical fields also show rotation property when the equiphases with gradient are dynamically and continuously imposed. This advantage of rotation also brings about the possibility of such chiral beams to rotate particles. Such beams would be advantageous for manufacturing tunable chiral metamaterials and have potential applications in optical tweezers and optical communication.     

Dielectric Chiral Metasurfaces for Second-Harmonic Generation with Strong Circular Dichroism

Dielectric chiral metasurfaces can generate harmonic waves with high efficiency and strong circular dichroism (CD), when they are supported by metallic substrates. Numerical results show that the second-harmonic generation (SHG) efficiency of about 10⁻³% for a peak pump intensity of about 5 GW cm⁻² can be achieved in the blue-UV, and the SHG CD reaches up to about 1.8, from a metasurface of Z-shaped lithium niobate nanoantenna array supported by gold substrate. Highly efficient and strong circular dichroic nonlinear responses are attributed to the plasmon-assisted local field enhancement in the dielectric chiral nanoantennae adjacent to the metallic substrate.     

A chiral granular gas

Inspired by rattleback toys, we created small chiral wires that rotate in a preferred direction on a vertically oscillating platform and quantified their motion with experiment and simulation. We demonstrate experimentally that angular momentum of rotation about particle centers of mass is converted to collective angular momentum of center-of-mass motion in a granular gas of these wires, and we introduce a continuum model that explains our observations.     

Left-handed chiral metamaterials

In this work, the concept of left-handed chiral metamaterials is analyzed by emphasizing their optical ability on the rotation of the plane of polarization of a wave. The possibilities of a negative phase velocity, negative and positive propagation constants, and basic electromagnetic properties of this novel medium are also presented. After the characterization of left-handed chiral metamaterial, we provide a reflection and transmission study for two planar boundaries of nonchiral-left-handed chiral metamaterial for normal angles of incidence. Some numerical results are also provided to validate the formulation found in the analysis and to show the role of the chirality in the propagation constants, phase velocities, reflection and transmission.      

原子核层次的手征对称性

对称性及其破缺是基本的科学问题。手征对称性在自然界中广泛存在,大至星系旋臂、行星自转,小到矿物晶体、有机分子、基本粒子,都与手征对称性密切相关。原子核层次的手征对称性概念于1997年提出,随后成为核物理研究的热点问题。目前,实验上已经在核素图上的80,100,130和190质量核区发现了30多例可能具有手征对称性的原子核。简要介绍原子核中的手征对称性概念;手性原子核的预言、识别以及实验验证;并通过展示手性原子核结构的多样性（M_χD）,回顾了理论和实验研究进展;介绍最新发现的原子核中手性和空间反射对称性的联立自发破缺,对未来手性原子核研究的前景进行了展望。Symmetry and its breaking are basic scientific problems. Chiral symmetries are common in nature, for example, the macroscopic spiral arms of galaxies and the rotation of planets; the microscopic spirals of the mineral crystalline, the organic molecules and the elementary particles. The concept of chirality in atomic nuclei was first proposed in 1997. Since then many efforts have been made to understand chiral symmetry and its spontaneous breaking in atomic nuclei. Up to now, more than 30 candidates of chiral nuclei have been reported in the 80, 100, 130, and 190 mass regions. The concept of the chirality in atomic nuclei, the prediction, the signal, and the experimental verification of the chiral nuclei are briefly introduced; the recent theoretical and experimental progress are reviewed, in particular the existence of multiple chiral doublets (M_χD), i.e., more than one pair of chiral doublet bands in one single nucleus; the simultaneous spontaneous breaking of chiral and reflection symmetry in the newly observed atomic nuclei is introduced, together with a prospect on the future study on nuclear chiral symmetry.     

单壁碳纳米管能带及其电子特性研究

从能带理论出发,采用电子紧束缚能量色散关系,推导锯齿,扶手椅和手性单壁碳纳米管(SWCNT)的电子能带结构表达式,指出单壁碳纳米管或为金属或为半导体的判据。结果表示:单壁碳纳米管的电子结构与其几何结构密切相关,如扶手椅型单壁碳纳米管是金属性的,而对其它类型的单壁碳纳米管是与碳纳米管的手性指数有关,只有手性指数n和m的差别等于3的倍数时,单壁碳纳米管是金属性的,否则会显出有带隙的半导体特性。这意味着单壁碳纳米管是由特殊的电子传输和光学性质,在纳米电子学领域具有巨大的潜在应用价值。