时间反演电磁波在金属丝阵列媒质中的超分辨率聚焦

本文利用一种已有的金属丝阵列结构, 验证了时间反演技术的时空聚焦特性, 并证明了在该阵列结构中, 时间反演电磁波具有超分辨率聚焦特性. 利用金属丝阵列能为凋落波提供传播渠道这一特性, 通过改变信号对时间反演镜的激励方式, 得到了多种亚波长异地成像的仿真结果. 本文的分析和仿真结果证实了利用时间反演技术, 可以采用传统的材料和设备, 在远场实现超分辨率聚焦成像, 并能在多个位置实现对源信号的提取和分析. 关键词： 时间反演 金属丝阵列 超分辨率聚焦 异地成像     

一种用于时间反演通信的亚波长天线阵列设计

基于时间反演电磁波的远场超分辨聚焦特性, 设计了一种亚波长天线阵列, 其天线单元刻蚀有微结构、单元间距为1/20工作波长且信道相互独立. 在保证相似的辐射特性的条件下, 该亚波长天线阵列对比于其他微结构刻蚀所组成的亚波长天线阵列, 具有较好的远场超分辨率聚焦特性. 为基于时间反演的高速率、高质量多天线通信提供了一种有效的终端天线阵列.     

基于远场时间反演的亚波长天线阵列研究

基于远场时间反演, 从信号处理角度对亚波长阵列的超分辨率聚焦特性进行了理论分析. 提出了一种新型的微结构刻蚀亚波长阵列, 通过时间反演聚焦实验表明, 该阵列具有远场超分辨聚焦特性, 各单元间信道相互独立. 将这种亚波长阵列应用在时间反演镜天线上, 通过实验验证了可以获得更好的超分辨率聚焦效果. 所提出的亚波长天线阵列对多天线超宽带无线通信具有潜在的应用价值. 关键词： 时间反演 亚波长 天线阵列 超分辨率     

时间反演镜对时间反演电磁波聚焦特性影响因素的研究

时间反演电磁波聚焦特性的主要影响因素来自于时间反演镜(time reversal mirror,TRM).利用电磁仿真工具,对各种影响因素进行分析,给出了改善时间反演电磁波聚焦特性的方法.最后,通过实验对改善方法的有效性进行了验证. 关键词： 时间反演镜 时间反演电磁波 聚焦特性 影响因素     

微波时间反演系统的空间超分辨率机理

时间反演系统中存在亚波长结构是系统展示空间超分辨特性的必要条件. 在近场, 信号是通过占主导地位的库仑场来传输的, 而库仑场的分辨率极限只与散射体的线度和空间分布有关, 因此可以突破微波衍射极限实现空间超分辨.     

基于多径信道模型研究时间反演腔的反演特性

基于时间反演腔的电磁波时间反演技术在许多方面有着潜在的应用,如脉冲压缩、功率合成、微扰探测、波束成形等.其中,时间反演腔通常采用具有多径传输特征的微波混沌腔.利用衍射理论,虽然可以证明这类腔体在时间反演过程中具有时空聚焦特性并可用于脉冲压缩,但是它不能用于分析腔体的反演性能.为了得到一个合适的分析方法并可用于指导时间反演腔设计,本文基于信道理论,分析电磁波传播的散射、扩散和衰减特性,构建了时间反演腔的多径信道模型,并详细研究了路径之间的串扰特征,给出反演重构信号的时间旁瓣产生机理、时移特征以及对主瓣的干扰情况.另外,根据随机平面波假设,还分析了空间焦斑的分布特征.实际焦斑大小不但受限于衍射极限而且还与初始焦斑大小有关.这些理论分析结果与实验和数值仿真结果基本一致.     

时间反演脉冲电磁波在双负材料中传播特性研究

利用全时域电磁仿真技术, 对比研究了时间反演脉冲电磁波和脉冲电磁波透过Smith结构双负材料后的时域波形、脉宽压缩以及材料内部空间电场峰值强度分布等时域传播特性. 结果表明：时间反演脉冲电磁波在透过双负材料后, 在初始源激励处表现出良好的时间和空间聚焦特性. 更重要的是, 在双负材料内部, 观测到了电场峰值强度减弱、截面电场峰值强度趋向均衡分布等新型的物理现象. 这些物理现象对发展能够承受大功率新型的双负材料电子器件及其应用系统很有参考研究价值.     

亚波长金属线阵中一维时间反演电磁波的聚焦机理研究

基于周期金属线阵的等效电介质模型, 并使用传输线理论方法, 得到了金属线阵中时间反演电磁波的解析表达式. 接着, 在等效电介质模型的适用范围内, 讨论了金属线半径、金属线阵周期、金属线阵周期数对时间反演电磁波聚焦的影响. 从而在理论上证实, 这种结构可以实现远场时间反演电磁波聚焦, 同时, 也为时间反演技术提供了工程参考.     

反激光器与光的捕获

时间反演对称性是经典电动力学与非相对论性量子力学的一种基本对称性,它描述的是时间反演后某些基本物理过程依然成立.例如,刚性光滑小球之间的碰撞过程在时间反演后仍然满足牛顿运动定律,然而微观尺度上摩擦力却导致了时间反演对称性破缺,即小球运动减慢与时间反演后加快不相符.推广到电磁场,一方面,真空中的电磁波传播就类似于无摩擦情况下的小球碰撞,满足时间反演不变性;另一方面,与电磁波相互作用的介质可以吸收电磁波,类似于摩擦力的作用,从而破坏了时间反演对称性.简单地说,吸收     

基于时间反演电磁波的微结构天线的单频点超分辨力聚焦研究

提出了在时间反演技术条件下单频的电磁波信号可以实现超分辨力聚焦这一思路,并基于信道理论推导了该思路的可行性;基于传统的同轴探针结构建立了间距为1/4波长的微结构模型,仿真结果证实了该模型结合时间反演技术在单频信号和宽带信号激励时均可以表现出超分辨力聚焦特性,理论分析和仿真结果为单频以及多频带天线的超分辨力聚焦特性的研究提供了重要的指导作用。     

Effect of fabrication errors on axial super-resolution property of a three-zone pupil filter

Two models have been established using the basic definitions of super-resolution characteristic parameters for normalized spot size G_A and Strehl ratio S_A, of a three-zone axial super-resolution pupil filter with fabrication errors, to quantitatively analyze the effect of these fabrication errors on the axial super-resolution property. These new models established to describe the analytic relationship of G_Ae and S_Ae of a pupil filter with its fabrication errors and its transmission function A(ρ), phase function φ(ρ) and structural parameters, directly relate the super-resolution parameters of a three-zone axial super-resolution pupil filter to its fabrication errors to make the quantitative analyses of the effect of fabrication errors easier, thereby providing a theoretical basis for the analysis, design and fabrication of a three-zone axial super-resolution pupil filter. The models established for G_Ae and S_Ae have been used to analyze the effect of the fabrication errors of a pupil filter on its super-resolution property, with a three-zone phase-only pupil filters as example.     

Effect of fabrication errors on lateral super-resolution property of a three-zone pupil filter

Two models have been established using the basic definitions of super-resolution characteristic parameters for normalized spot size G_T and Strehl ratio S_T of a three-zone lateral super-resolution pupil filter with fabrication errors to quantitatively analyze the effect of these fabrication errors on the lateral super-resolution property. These new models established to describe the analytic relationship of G_Te and S_Te of a pupil filter with its fabrication errors and its transmission function A(ρ), phase function φ(ρ) and structural parameters directly relate the super-resolution parameters of a three-zone lateral super-resolution pupil filter to its fabrication errors to make the quantitative analyses of the effect of fabrication errors easier, thereby providing a theoretical basis for the analysis, design and fabrication of a three-zone lateral super-resolution pupil filter. The models established for G_Te and S_Te have been used to analyze the effect of the fabrication errors of a pupil filter on its super-resolution property with a three-zone phase-only pupil filter as an example.     

Time-reversal multiple signal classification in case of noise: a phase-coherent approach

The problem of locating point-like targets beyond the classical resolution limit is revisited. Although time-reversal MUltiple SIgnal Classification (MUSIC) is known for its super-resolution ability in localization of point scatterers, in the presence of noise this super-resolution property will easily break down. In this paper a phase-coherent version of time-reversal MUSIC is proposed, which can overcome this fundamental limit. The algorithm has been tested employing synthetic multiple scattering data based on the Foldy-Lax model, as well as experimental ultrasound data acquired in a water tank. Using a limited frequency band, it was demonstrated that the phase-coherent MUSIC algorithm has the potential of giving significantly better resolved scatterer locations than standard time-reversal MUSIC.     

Super-Resolved Raman Spectroscopy

In this paper we present a super-resolved Raman spectroscopy configuration where, due to the proposed resolution improvement, more chemical species can be simultaneously detected. The idea includes usage of the basic property of Raman in which shifting the excitation wavelength will shift the absolute wavelength of the Raman spectral lines. Thus, encoding the spectra prior to analysis by the spectrometer allows obtaining spectral super-resolved sensing via time multiplexing super-resolution concepts applied over the spectral domain.     

基于半像素错位的多幅图像重建高分辨率图像技术研究

介绍了一种基于半像素错位的多幅图像重建高分辨率图像技术。分析了半像素错位的多幅图像与高分辨率图像各像素灰度值的对应关系 ,并从CCD数字化采样的角度进行了论证。同时 ,结合实际摄像机CCD结构 ,求出了高分辨率图像重建的计算公式 ,并通过实验进行了验证和完善。重建的本质是以原高分辨率图像的 4邻域平均图像为基础 ,增加一定比例的边缘细节信息 ,去接近原高分辨率图像。CCD的动态范围越大 ,图像的灰度级越多 ,那么计算误差就越小 ,图像的边缘细节信息就可以利用更多 ,重建的图像就越接近原高分辨率图像。通过实验和分析表明 ,利用半像素错位的多幅低分辨率图像重建高分辨率图像的原理是正确的 ,方案是可行的     

Near-field multiple super-resolution imaging from Mikaelian lens to generalized Maxwell's fish-eye lens

Super-resolution imaging is vital for optical applications, such as high capacity information transmission, real-time bio-molecular imaging, and nanolithography. In recent years, technologies and methods of super-resolution imaging have attracted much attention. Different kinds of novel lenses, from the superlens to the super-oscillatory lens, have been designed and fabricated to break through the diffraction limit. However, the effect of the super-resolution imaging in these lenses is not satisfactory due to intrinsic loss, aberration, large sidebands, and so on. Moreover, these lenses also cannot realize multiple super-resolution imaging. In this research, we introduce the solid immersion mechanism to Mikaelian lens (ML) for multiple super-resolution imaging. The effect is robust and valid for broadband frequencies. Based on conformal transformation optics as a bridge linking the solid immersion ML and generalized Maxwell's fish-eye lens (GMFEL), we also discovered the effect of multiple super-resolution imaging in the solid immersion GMFEL.     

Si掺杂Ag基超分辨薄膜读出性能研究

超分辨薄膜是一种能够实现突破光学衍射极限的功能薄膜,它在超分辨近场光存储技术中起到至关重要的作用。采用磁控溅射共溅的方式制备了Ag掺杂一定量Si的超分辨复合薄膜,测试了其作为掩膜层的超分辨光盘读出性能,并获得了最佳的薄膜制备条件,即当Ag溅射功率为55 W,Si为95 W,溅射时间为80s,薄膜厚度为39nm时,超分辨光盘的读出信号载噪比(CNR)最高为28dB。用X射线光电子能谱测量了上述薄膜的组成,用扫描电子显微镜观察了薄膜微区形貌,并用椭圆偏振光谱仪测量了薄膜的光学常数和厚度。超分辨复合薄膜的读出机理可以用Ag的散射型机理解释。光盘在持续读出10万次以后读出信号基本没有下降。