Co/Si多层膜的磁控溅射及其X射线衍射分析

用超高真空磁控溅射设备在不同溅射压强及衬底温度的工艺条件下制备了一系列Ｃｏ／Ｓｉ多层膜．Ｘ射线小角衍射证实所研制的多层膜具有周期调制结构．分别采用不同的理论方法计算了多层膜的周期和折射修正项．表明修正项不再仅对折射效应修正,而应理解为更广义的修正项．并应用广义修正总多层膜厚度Ｂｒａｇｇ公式确定出了主峰之间次峰的级数．     

磁控溅射Si/Co多层膜的小角X射线衍射测试研究

用小角X射线衍射方法对Si/Co多层膜进行了测试研究,应用衍射理论对测试中出现的周期数不多的强峰和其间的一系列次强峰进行了分析,在计算多层和单层膜厚度时,提出利用相邻两个衍射峰的角度之差来消除系统误差和定位误差的简便方法,使数据处理得到简化.最后,通过XPS分析指出,在膜层界面具有硅的化合物存在.     

磁控溅射Si／Co多层膜的小角X射线衍射测试研究

用小角X射线衍射方法对Si/Co多层膜进行了测试研究,应用衍射理论对测试中出现的周期数不多的强峰和其间的一系列次强峰进行了分析,在计算多层和单层膜厚度时,提出利用相邻两个衍射峰的角度之差来消除系统误差和定位误差的简便方法,使数据处理得到简化。最后,通过XPS分析指出,在膜层界面具有硅的化合物存在。     

宽波带高反射率介质膜的研究

本文从多层介质薄膜的特征矩阵方程出发概述了反射率透过率计算的一般理论。对于以λ／４高折射率介质和λ／４低折射率介质为基本周期的膜系的高反射率波带宽度进行了分析。给出利用一个中心波长λ／４膜系迭加另一个中心波长λ／４膜系中间插入补偿层的展宽波带的方法。 理论计算表明，在Ｋ－９玻璃上高折射率介质用硫化锌，低折射率介质用氟化镁，用两个１５层的λ／４膜系中间插入一层补偿层即可得到覆盖可见光区的宽波带高反射率。 在真空镀膜机上研制的膜片实测结果与理论计算基本相符。文中介绍了镀膜工艺的特点。所镀制的宽波带激光反射镜用于氦镉空阴极放电白激光器得到４４１６Ａ，５３Ｔ８Ａ，６３６０Ａ等多谱线激光输出大于５０毫瓦。     

射频溅射中氩气压强对Ge/Si多层膜的影响

用射频磁控溅射制备了一系列Ｇｅ／Ｓｉ多层膜,采用Ｘ射线小角衍射测量了不同溅射压强下制备的样品,计算出了多层膜的周期．通过计算机模拟实验曲线确定出了Ｇｅ和Ｓｉ的分层厚度,计算出了不同压强下的溅射速率．实验和计算机模拟都表明了在衬底温度为５９０℃、溅射功率为１５０Ｗ的溅射条件下１．５～２．５Ｐａ氩气压强时制备出的样品周期性、均匀性和平整性都比其它压强下制备的样品好．     

多层高反膜的理论设计与光学特性分析

从理论上对光学多层介质反射膜作了设计，用堆积密度的概念模拟了溶胶-凝胶法制备的纳米多孔薄膜的折射率；利用反射率增幅分析与膜层制备难度分析来选择理想的膜系设计；通过计算分析了经典四分之一波长膜系的光学特性，包括薄膜膜层的驻波场分布和镀膜过程中的随机误差对膜层反射率曲线的影响，为多层高反膜的化学法制备与实际应用提供了重要依据。     

多层高反膜的理论设计与光学特性研究

利用软件Essential Macloed对光学多层介质反射膜作了理论设计：用packing density的概念模拟了多孔薄膜,实现了材料折射率的可调节;通过计算分析了非四分之一波长膜系的光学特性,得出倍频反射带反射率随高折射率膜层厚度变化的关系,该结果对于特殊膜系的设计具有一定的理论指导意义。     

Fe-N/TiN纳米多层膜的结构与力学特性

该文用磁控溅射法制备了一系列Fe-N/TiN纳米多层膜;利用广角和小角X射线衍射和俄歇电子能谱对多层膜的微观结构和成分进行了测试;利用纳米硬度计和纳米划痕仪研究了多层膜的微观力学性能。固定Fe-N层厚度为20nm,改变TiN层的厚度,研究了TiN层厚度变化对Fe-N/TiN纳米多层膜的附着力、硬度、弹性模量等性能的影响。发现TiN层为2nm时多层膜有最好的力学性能,说明对Fe-N/TiN多层膜来说,对力学性能影响最大的是多层膜的调制周期。     

由正负折射率材料构成的Thue-Morse序列光子晶体的共振光传输

讨论了由正折射率材料和负折射率材料构成的Thue-Morse序列光子晶体的共振光传输特性。利用传输矩阵法，得到传输矩阵元的逆推关系式及透射率。数值计算结果表明，类似于普通材料构成的TM序列光子晶体，含负折射率材料的此种多层系统的完全透射态也存在自相似排列。     

含负折射率材料缺陷的一维光子晶体的透射性质

利用传输矩阵方法模拟了含负折射率材料缺陷的多层膜体系的透射率,发现这种结构具有高Q值的多共振透射峰。     

从负折射超材料到光学隐身衣

1964年俄罗斯科学家V.Vesalago从Maxwell方程组出发断言具有负折射率的左手材料(LHM)可以存在,1996年和1999年J.Pendry提出了LHM的初始设计。2000年D.Smith制成首个LHM,它可把微波波束弯折到与常规的不同方向。近年来LHM吸引了人们的兴趣,它也称为超材料,但在自然界并不存在。它可变更电磁波传播,从而造成负折射甚至隐形。一个时期以来,在微波和光频进行的隐身斗篷实验是2D或3D的,它们与通常的隐形方法显著不同。LHM的其他应用如左手传输线、成像技术等。本文首先对负折射研究和隐身衣设计的历史和进展作回顾,进而讨论了这些领域中理论与实验工作的意义。可以看出负折射问题是非常复杂的。还讨论了负折射与负波速、负折射与负GH位移的关系。     

Three-dimensional optical metamaterial with a negative refractive index

Metamaterials are artificially engineered structures that have properties, such as a negative refractive index, not attainable with naturally occurring materials. Negative-index metamaterials (NIMs) were first demonstrated for microwave frequencies, but it has been challenging to design NIMs for optical frequencies and they have so far been limited to optically thin samples because of significant fabrication challenges and strong energy dissipation in metals. Such thin structures are analogous to a monolayer of atoms, making it difficult to assign bulk properties such as the index of refraction. Negative refraction of surface plasmons was recently demonstrated but was confined to a two-dimensional waveguide. Three-dimensional (3D) optical metamaterials have come into focus recently, including the realization of negative refraction by using layered semiconductor metamaterials and a 3D magnetic metamaterial in the infrared frequencies; however, neither of these had a negative index of refraction. Here we report a 3D optical metamaterial having negative refractive index with a very high figure of merit of 3.5 (that is, low loss). This metamaterial is made of cascaded 'fishnet' structures, with a negative index existing over a broad spectral range. Moreover, it can readily be probed from free space, making it functional for optical devices. We construct a prism made of this optical NIM to demonstrate negative refractive index at optical frequencies, resulting unambiguously from the negative phase evolution of the wave propagating inside the metamaterial. Bulk optical metamaterials open up prospects for studies of 3D optical effects and applications associated with NIMs and zero-index materials such as reversed Doppler effect, superlenses, optical tunnelling devices, compact resonators and highly directional sources.     

Photonic crystals: imaging by flat lens using negative refraction

The positive refractive index of conventional optical lenses means that they need curved surfaces to form an image, whereas a negative index of refraction allows a flat slab of a material to behave as a lens and focus electromagnetic waves to produce a real image. Here we demonstrate this unique feature of imaging by a flat lens, using the phenomenon of negative refraction in a photonic crystalline material. The key advance that enabled us to make this observation lies in the design of a photonic crystal with suitable dispersion characteristics to achieve negative refraction over a wide range of angles.     

A Newtonian approach to extraordinarily strong negative refraction

Metamaterials with negative refractive indices can manipulate electromagnetic waves in unusual ways, and can be used to achieve, for example, sub-diffraction-limit focusing, the bending of light in the 'wrong' direction, and reversed Doppler and Cerenkov effects. These counterintuitive and technologically useful behaviours have spurred considerable efforts to synthesize a broad array of negative-index metamaterials with engineered electric, magnetic or optical properties. Here we demonstrate another route to negative refraction by exploiting the inertia of electrons in semiconductor two-dimensional electron gases, collectively accelerated by electromagnetic waves according to Newton's second law of motion, where this acceleration effect manifests as kinetic inductance. Using kinetic inductance to attain negative refraction was theoretically proposed for three-dimensional metallic nanoparticles and seen experimentally with surface plasmons on the surface of a three-dimensional metal. The two-dimensional electron gas that we use at cryogenic temperatures has a larger kinetic inductance than three-dimensional metals, leading to extraordinarily strong negative refraction at gigahertz frequencies, with an index as large as -700. This pronounced negative refractive index and the corresponding reduction in the effective wavelength opens a path to miniaturization in the science and technology of negative refraction.     

负折射物质特性的理论分析

从基本的电磁场理论出发,分析和解释负折射物质的电磁特性,以及负折射物质中的逆Cerenlov现象、逆Doppler现象、负折射率和完美透镜的工作原理,帮助人们更加清楚地认识负折射物质的本质特性,更好地开发和应用好负折射物质.     

一种电波折射订正方法及其在高空风探测中的应用

为提高无线电测风的精度,在根据二维射线追踪法的基础上,建立了适用于球面分层大气的电波折射高精度在线订正方法,并对电波折射误差及高空风探测误差进行了模拟计算和分析.结果表明,电波折射产生的仰角、斜距和高度误差通常为正值,3类误差均随仰角减小和斜距增大而增大;在低仰角和大斜距的条件下,电波折射误差大于定位设备误差,当仰角低...     

A terahertz metamaterial with unnaturally high refractive index

Controlling the electromagnetic properties of materials, going beyond the limit that is attainable with naturally existing substances, has become a reality with the advent of metamaterials. The range of various structured artificial 'atoms' has promised a vast variety of otherwise unexpected physical phenomena, among which the experimental realization of a negative refractive index has been one of the main foci thus far. Expanding the refractive index into a high positive regime will complete the spectrum of achievable refractive index and provide more design flexibility for transformation optics. Naturally existing transparent materials possess small positive indices of refraction, except for a few semiconductors and insulators, such as lead sulphide or strontium titanate, that exhibit a rather high peak refractive index at mid- and far-infrared frequencies. Previous approaches using metamaterials were not successful in realizing broadband high refractive indices. A broadband high-refractive-index metamaterial structure was theoretically investigated only recently, but the proposed structure does not lend itself to easy implementation. Here we demonstrate that a broadband, extremely high index of refraction can be realized from large-area, free-standing, flexible terahertz metamaterials composed of strongly coupled unit cells. By drastically increasing the effective permittivity through strong capacitive coupling and decreasing the diamagnetic response with a thin metallic structure in the unit cell, a peak refractive index of 38.6 along with a low-frequency quasi-static value of over 20 were experimentally realized for a single-layer terahertz metamaterial, while maintaining low losses. As a natural extension of these single-layer metamaterials, we fabricated quasi-three-dimensional high-refractive-index metamaterials, and obtained a maximum bulk refractive index of 33.2 along with a value of around 8 at the quasi-static limit.     

激光到达角误差修正方法研究

由于大气介质的不均匀性,导致大气折射率不再是常数,使得激光在大气中传播时产生折射效应,最终使激光束到达角产生误差,影响系统的通信性能.为了减小到达角产生的误差,提高系统的性能,提出了一种利用纯转动拉曼激光雷达修正对流层目标定位误差的方法,根据角度折射误差来调整光源仰角的方法.通过对新方法仿真计算证实,在进行远距离光通信时,经过大气折射误差修正后,可以在很大程度上提高光通信的速率,减小误码率.     

基底温度对Ti/TiN薄膜内应力的影响研究

摘要：采用反应直流磁控溅射法,在硅基底上制备了一系列不同结构的Ti/TiN多层薄膜。采用X射线衍射仪（XRD）对薄膜物相进行了分析,研究了溅射沉积过程中基底温度对周期薄膜结构及内应力的影响.结果表明：多层薄膜中的Ti出现（101）面,TiN的（200）面衍射峰强度在基底温度为600℃时为最高。随着衬底温度的升高,薄膜内部的压应力逐渐减小,当基底温度在600℃时,薄膜内应力最小。