共查询到20条相似文献,搜索用时 93 毫秒
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《光学学报》2015,(11)
基于倏逝波理论和光学谐振原理,研究了倏逝波在光子晶体中的存在形式及空气栅光子晶体F-P腔的折射率传感机理,并建立谐振波长与待测气体折射率的关系模型。当入射光以大于全反射临界角的角度入射到光子晶体中,由于倏逝波的作用,在中心介质层形成F-P腔并产生谐振,电磁场被局部增强,与待测气体充分作用,从而使该传感结构对待测气体的折射率具有较高的敏感性。利用传输矩阵理论进行数值模拟,结果表明,折射率传感的Q值可达3447.0,灵敏度可达1260.0 nm/RIU,证明该光子晶体F-P腔折射率传感结构具有很好的传感特性,可为高精度气体折射率传感器的设计与应用提供一定的理论参考。 相似文献
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空间移频超分辨成像技术利用样品表面的微纳结构对照明倏逝波的散射,使其转换为传播波,并将倏逝波携带的高频空间信息转换成低频信息,可被远场的显微物镜所接收,实现超分辨成像.其极限分辨率由照明的倏逝波波长决定,但分辨率仅在倏逝波波矢方向上有提升.在现有的棱镜全反射倏逝波生成方案中,倏逝波的最短波长受棱镜折射率的限制,因此其最高分辨率也受限制;且生成的倏逝波波矢为单一方向,因此分辨率存在方向差异性.为解决上述问题,建立了完整的空间移频超分辨成像仿真模型,并提出了一种新型倏逝波生成方案,可利用微纳结构产生波长更短、具有全方向波矢的倏逝波.结果显示,新方案可产生波长更短的倏逝波,并消除成像分辨率的方向差异性,从而避免现有方案中的多方位成像和图像后处理.空间移频超分辨成像技术具有大视场、高分辨、结构简单、操作方便、无需逐点扫描、可与普通光学显微镜兼容等优点,改进后将具有更广阔的应用空间. 相似文献
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由于衍射极限的存在,传统光学透镜成像分辨率理论上只能达到入射光波长的一半。通过恢复和增强携带物体细部特征信息的高频倏逝波,基于表面等离子体的平面金属透镜有望突破这种光学衍射极限,实现超分辨成像。本文对平面薄膜式与纳米结构式两类平面金属透镜进行了综述,详细介绍了若干典型平面金属透镜的结构设计、工作机理及其聚焦性能,并对其特点与存在的问题进行了分析与讨论。由于光波在金属中传播时存在一定损耗,如何更高效地增强高频倏逝波信号并转换成传播波,使其参与成像,以更好地实现远场超分辨成像,以及如何进一步增大近场超高分辨率聚焦光斑焦深以及减小远场聚焦光斑尺寸,是表面等离子体平面金属透镜进一步研究的重点。 相似文献
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本文展示一种由两根微米光纤构成的耦合型环境折射率传感器。微米光纤表面存在倏逝波,芯外介质折射率微小的改变将引起倏逝场分布变化,从而导致能量在耦合器两臂中的重新分配。本文通过测量耦合器两端出射光功率的比值来对葡萄糖溶液的浓度进行传感,实验结果表明该微米光纤耦合型传感器的浓度传感灵敏度可达1.58 mol·L~(-1)。本文用耦合模理论详细分析了两根相邻微米光纤的耦合效率与芯外介质折射率之间的关系,发现减小耦合区的光纤的直径,增大入射光波长或增大耦合长度,都可以进一步提高这种传感器的灵敏度。 相似文献
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银金属在特定波长范围内的负折射率性质可以放大倏逝波,在近场成像中能够保留次波长信息,因此是制造"完美透镜"的优良材料。由银金属和其他介质组成的复合材料能够通过其调整体积分数来改变"完美透镜"的工作波长,使其在可见光和近红外范围内实现完美成像。除体积分数外,复合材料中金属颗粒的大小和形状也会对透镜的工作波长和成像质量有影响。在考虑尺寸效应修正的基础上,通过分析尺寸对成像性质的影响发现:减小金属颗粒尺寸会使工作波长发生蓝移,当银颗粒尺寸减小到10nm时,会显著降低成像质量。 相似文献
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We report analytical calculations for the propagation of electromagnetic radiation through an inhomogeneous layer whose refractive index varies in one-dimension situated between bulk right- and left-handed media. Significant field localization is generated in the layer that is caused by the coherent superposition of evanescent waves. The strength of the field localization and the transmission properties of the layer are investigated as a function of the layer width, losses and defects in the refractive index; the former two being modelled by continuous changes, and the latter by discontinuous changes, in the index profile. 相似文献
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Hala J. El-Khozondar Rifa J. El-Khozondar Said Zouhdi 《Applied Physics A: Materials Science & Processing》2012,109(4):865-867
The surface wave propagation at the interface between tunable metamaterials (MTMs) and nonlinear media is investigated. Tunable MTMs have a refractive index which can be tuned to negative?Czero?Cpositive values. The nonlinear media are assumed to have a Kerr-like refractive index. The dispersion equation is analytically derived and solved numerically. Results display the different behaviors of the propagating waves as the refractive index is tuned. 相似文献
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分析了隐失波透过负折射率材料制成的透镜时,可以实现相位的调整,从而实现波的聚焦的原理;另外利用叠加原理(干涉法)及场量匹配法分析了负折射率材料如何实现对隐失波的振幅的放大,得到负折射率材料对隐失波有幅度增益,行波和隐失波都能聚焦成像的结论;并利用传输线理论提出隐失波透过负折射率材料平板时可等效地形成一个LC振荡电路,从而实现对隐失波的幅度增益. 相似文献
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微波异常传播中的负折射率问题 总被引:10,自引:0,他引:10
给出关于电磁波折射率理论的评述,重点介绍了美国圣迭戈加州大学(UCSD)研究组关于负折射率的实验,该实验证明左手化物质(LHM)确实呈现负折射率。 相似文献
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Wave propagation through curved bends in integrated optical waveguides is governed by the evanescent field and the radiation loss of the eigenmodes. Since these parameters are influenced by the refractive index of the surrounding medium, circular bends in rib waveguides have been successfully employed as chemical sensors for liquids and gases. In this paper the electromagnetic field, the refractive index and the radiation loss of the eigenmodes are precisely determined by a fully vectorial approach based on the method of lines. An axial discretization and Bessel functions of complex order are employed for the rigorous computation of the evanescent field. The intensity distributions of the first modes in a rib waveguide are presented. The influence of the rib height on the sensitivity of the modal index to the refractive index of the surrounding medium is investigated. The results are useful for the optimization of the sensor design. 相似文献
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Propagation and tunneling of light through photonic barriers formed by thin
dielectric films with continuous curvilinear distributions of dielectric
susceptibility across the film, are considered. Giant heterogeneity-induced
dispersion of these films, both convex and concave, and its influence on
their reflectivity and transmittivity are visualized by means of exact
analytical solutions of Maxwell equations. Depending on the cut-off
frequency of the film, governed by the spatial profile of its refractive
index, propagation or tunneling of light through such barriers are examined.
Subject to the shape of refractive index profile the group velocities of EM
waves in these films are shown to be either increased or deccreased as
compared with the homogeneous layers; however, these velocities for both
propagation and tunneling regimes remain subluminal. The decisive influence
of gradient and curvature of photonic barriers on the efficiency of
tunneling is examined by means of generalized Fresnel formulae. Saturation
of the phase of the wave tunneling through a stack of such films (Hartman
effect), is demonstrated. The evanescent modes in lossy barriers and
violation of Hartman effect in this case is discussed. 相似文献
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G. Brida M. Genovese M. G. A. Paris F. Piacentini E. Predazzi E. Vallauri 《Optics and Spectroscopy》2007,102(1):90-97
The propagation of pulses of the pump and its second harmonic in a quadratically nonlinear medium whose linear properties are characterized by a negative refractive index at the pump frequency and by a positive refractive index at the harmonic frequency is considered theoretically. In the case of a low intensity of the interacting waves, the pump and second-harmonic pulses propagate in the opposite directions, but sufficiently powerful pulses can form a simulton—a solitary two-frequency wave propagating in a certain direction as a single whole. Solutions to a set of equations are found which describe the steady-state propagation of a solitary wave and of a nonlinear periodic (cnoidal) wave. 相似文献
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We theoretically studied a left-hand structure based on a two-dimensional (2D) photonic crystal (PC)with a negative refractive index. The propagation of electromagnetic waves in the proposed PC structure is investigated through dispersion characteristic analysis and numerical simulation of field pattern. The designed PC structure can exhibit all angle negative refraction, and the corresponding effective refractive indices along all directions are almost same and close to the ideal value of -1. A flat lens formed from such a PC has been designed and its imaging properties have been investigated systematically. 相似文献
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M. V. Golovkina 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(12):1669-1673
The propagation of electromagnetic waves in a rectangular waveguide containing layers of common dielectric and metamaterial
with a negative refractive index separated by a thin film of a superconductor of the second type in the mixed state is considered.
The possibility of amplifiying waves at frequencies lower than the cutoff energy due to the energy of an Abrikosov vortex
lattice moving in the superconductor is demonstrated. 相似文献