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《物理学报》2016,(15)
本文设计了一种单层高效透射型相位梯度超表面,并通过仿真和实验进行了验证.在圆极化波入射条件下,超表面单元的交叉极化转化率大于90%的频带范围为14-15.8 GHz.通过对单元的面内旋转可实现在保持高交叉极化透射幅度的前提下对交叉极化透射相位进行调控.基于6个旋转步进为300的超表面单元周期排布设计了一维相位梯度超表面,该超表面对左/右旋圆极化波分别形成方向相反的相位梯度,因此线极化波经过超表面后将会分离成两束对称传播的圆极化波15 GHz处的近场电场分布和远场归一化透射能量方向图的仿真结果表明,奇异透射角仿真值为33.50,与理论设计值(33.75°)符合得很好.仿真并测试了透射功率密度谱,结果表明在14.9-15.3GHz频带范围内垂直入射的线极化波被高效分离成两束圆极化波.相比于以往的透射型极化调制超表面,该超表面具有工作效率高、厚度薄、重量轻等优点,在电磁波传播和极化操控领域具有重要的应用价值. 相似文献
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基于金属-光敏硅组合圆环提出了一种光可调太赫兹超表面,可用于实现多功能的波前操控。该超表面单元由正反两面的结构层和中间介质层组成,其中结构层是开口方向相反的金属环,开口处由光敏硅进行填充。在光照强度较低时,超表面可以将入射的圆极化波转换为交叉极化的透射波;随着光照强度升高,透射波将逐渐被完全抑制。根据几何相位原理,通过旋转金属-光敏硅组合圆环,透射的交叉极化波会携带额外的相位因子,并可实现完全的2π范围相位覆盖。通过合理排列超表面单元结构,可以对透射波的波前实现任意操控。利用提出的光可调超表面,在较低光照条件下实现了高效的异常折射、透镜以及轨道角动量产生器;在较高光照条件下,抑制了其透射效率,可有条件地选择应用功能,表现出较好的灵活性。提出的光可调超表面在太赫兹成像、通信、雷达等方面具有较大的潜在应用价值。 相似文献
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提出了一种基于双开口谐振环单元结构超表面的太赫兹宽带涡旋光束产生器.该结构由金属-电介质两层构成,位于顶层的是基于双开口谐振环单元结构的超表面,底层为介质层.对单元结构阵列进行数值仿真,圆偏振的入射光可以被转换成相应的交叉偏振透射光,通过旋转表层金属谐振环,可以控制交叉偏振透射光具有相同的振幅和不同的相位.这些单元结构按照特定的规律排列,可以形成用以产生不同拓扑荷数的涡旋光束的涡旋相位板.以拓扑荷数1和2为例,设计了两种涡旋相位板,数值分析了圆偏振波垂直入射到该涡旋相位板生成交叉圆偏振涡旋光束的特性.结果表明,在1.39—1.91 THz的频率范围内产生了比较理想的不同拓扑荷数的涡旋光束,且透过率高于20%,最高可达到24%,接近单层透射式超表面的理论极限值. 相似文献
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利用相变材料嵌入超表面组成复合结构实现太赫兹移相器,该器件自上而下依次为二氧化钒嵌入金属层、液晶、二氧化钒嵌入金属层、二氧化硅层.通过二氧化钒的相变特性和液晶的双折率特性同时作用实现对器件相位调控.随着外加温度变化二氧化钒电导率发生改变,器件的相位随之产生移动,同样的对液晶层施加不同的电压导致液晶折射率发生变化,器件相位也会有影响.经过这两种介质共同作用,最终实现对太赫兹波相位有效调控.仿真结果验证了该相移器在频率f=0.736 THz时,太赫兹移相器的最大相移量达到355.37°,在0.731—0.752 THz(带宽为22 GHz)频率范围相移量超过350°.这种基于相变材料与超表面复合结构为灵活调控太赫兹波提供了一种新思路,将在太赫兹成像、通信等领域有着广泛的应用前景. 相似文献
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提出了一种具有独立调控透射幅值与相位能力的新型惠更斯单元结构,能够实现透射幅值在0~0.9、透射相位在0~2π的任意调控.基于广义斯涅耳定理对惠更斯单元进行排列,设计并制备出具有异常透射功能的超表面结构.全波仿真结果表明超表面能够使频率为10 GHz的正入射电磁波产生约60°的偏折.近场测试结果与仿真结果基本一致,进一... 相似文献
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在线性光学范畴内,人们已经通过亚波长尺度的超薄超构表面成功实现了对光的众多新颖特性的调控功能.其主要理念是通过对具有亚波长尺度且空间方向变化的超构功能基元进行特定的排列,从而实现对光的偏振、相位和振幅的有效控制.近来,超构表面上的非线性光学特性也引起了大家的广泛关注.在本综述中,我们对非线性光学超构表面的设计、超构功能单元的材料和对称性选择、非线性手性光学、非线性贝里几何相位和非线性波前整形等内容进行了总结;最后对非线性光学超构表面在调控光与物质的相互作用中面临的挑战和前景进行了展望. 相似文献
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In this paper a flat structurally tunable acoustic metasurface is constructed based on the helical unit cell. The length of the acoustic channel can be tuned by the screw-in depth of the helix. Accordingly, the wave phase for the transmitted acoustic wave can be tuned and the wavefront can be manipulated. Then multifunctions such as anomalous refraction, point focusing, beam focusing and self-bending can be realized and switched just by screwing in or out the helixes. At the same time, the broadband operating frequency is also realized. The experiments for anomalous refraction and point focusing are also performed, and the results show that the designed metasurface is effective. The present studies have important applications in dynamic manipulation of acoustic waves by metasurfaces. 相似文献
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Jian-Wen Dong 《Physics letters. A》2008,372(24):4532-4535
Multiple omnidirectional resonances are found in a sandwich structure consisting of a left-handed metamaterial cavity and two single-negative-permittivity reflection walls. These resonances appear because the phase shift of left-handed metamaterial can cancel the reflection phase shift of single-negative-permittivity metamaterials at every incidence angle. By using such particular structure, a kind of structure possessing multiple omnidirectional resonances in both polarizations has been designed. In addition, issues associated with energy loss are discussed. 相似文献
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In this Letter, we investigate giant and negative bistable lateral shifts for a light beam transmitted through a one-dimensional photonic crystal containing a nonlinear metamaterial defect. It is shown that there exists a typical S-shaped curve of the normalized input-output intensity. The hysteresis of lateral shift, resulting from the reshaping effect (constructive and destructive interferences of each plane wave components undergoing different phase shifts) is dependent on the nonlinear defect, the incident intensity and incidence angle. Numerical simulations are also made for the validity of stationary phase approach. All these phenomena lead to potential applications in integrated optics and optical switches. 相似文献
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在CH_2~+体系的电子基态势能面上运用准经典轨线方法,研究了当碰撞能E=500 me V时,反应物分子的振动激发对H(~2S)+CH~+(X~1Σ~+)→C+(~2P)+H_2(X1_gΣ~+)反应的反应概率、反应截面和立体动力学性质的影响.分别计算了两矢量相关k-j′的P(θ_r)分布,三矢量相关k-k′-j′的P(φr)分布以及反应产物的四个极化微分截面.结果表明,产物分子转动角动量不仅在Y轴方向有取向效应,还定于Y轴的正方向.并且发现,随着振动量子数的增加,对反应体系产物分布的影响就越明显. 相似文献
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A three-dimensional chiral metamaterial with four-fold rotational symmetry is designed, and its optical properties are investigated by numerical simulations. The results show that this chiral metamaterial has the following features: high polarization conversion, perfect circular dichroism, and asymmetric transmission of circularly polarized light. A comparison of the results of chiral metamaterials without and with weak coupling between the constituent nanostructures enables us to confirm that the optical properties of our proposed nanostructure are closely related to the coupling between the single nanoparticles. This means that the coupling between nanoparticles can enhance the polarization conversion, circular dichroism, and asymmetric transmission. Due to the excellent optical properties, our metamaterial might have potential applications in the development of future multi-functional optical devices. 相似文献
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A cold atomic medium(Rydberg medium) with cascade configuration under the blockade mechanism is considered. A partial coherent light(PCL) beam is incident on the medium, which makes an angle θ with z-axis. We study the influence of PCL field on the transmission spectrum and find high transmission of probe field for PCL field.Conversely, it is investigated that the transparency of probe field decrease for coherent light field. The transmission of probe field is also studied via beam width of PCL field and investigated high transmission of probe field for small beam width and vice versa. Interestingly, the Goos-H?nchen shift(GHS) in the transmitted light(TL) is studied for PCL field. Large negative and positive GHS in the TL are investigated for PCL field and small beam width of PCL field. 相似文献
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本文通过设计出一种反射型极化旋转超表面,在8—12 GHz频域内实现高效的极化旋转,并将其加载于微带缝隙天线下方构成新型的极化旋转超表面天线,利用超表面的90°极化旋转效应,成功实现了天线的圆极化辐射调制.仿真与实验结果表明:圆极化天线的中心工作频率为GHz,阻抗带宽为8.3—10 GHz.当微带缝隙天线与极化旋转超表面的间距H=4.5mm时,天线在8.3—8.8 GHz频带内实现了圆极化辐射;当mm时,天线在8.8—9.3 GHz频带内实现了圆极化辐射;当=8mm时,天线在9.3—10 GHz频带内实现了圆极化辐射.实验结果与仿真结果相符,证明了此种设计方法的有效性,也为微带缝隙天线的圆极化设计提供了一种新的途径. 相似文献
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We use numerical methods to study the model x(n+l)=λx(n) (x(n)-1)+ef(θ(n),φ(n)),θ(n+1)=θ(n)+A, φ(n+1)=φ(n)+B. As e is small, we get doubled three-tori. Increasing e the tori become fractal three-tori, the dimension is not integer, while the trajectory does not diverge exponentially. Finally it changes into chaos. The critical parameter values.for chaos are approximately calculated. So one of the roads from three-tori to chaos is three-tqri→fractal three-tori (not chaos)→chaos. 相似文献
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Diffraction of monochromatic light on a grating leads to the attenuation of the transmitted beam of diffraction order zero. In the case of a thick grating the diffraction efficiency, and hence the effective attenuation coefficient, is a fast-varying function of the Bragg mismatch angle. According to Kramers-Kronig theory, the transmitted beam encounters a phase shift that also depends on the mismatch angle. This phase shift is measured for holographic gratings in a photoaddressable block copolymer and compared with analytical calculations. 相似文献