Analysis and design of LC amplifiers and LC oscillators using current-feedback amplifiers

The present paper discusses specific types of LC amplifier and LC oscillator using a current-feedback amplifier (CFA). The main advantage of the CFAs versus voltage-feedback amplifiers (VFAs) is their gain-bandwidth independence. Some of the monolithic CFAs provide an additional pin between the first stage (current-controlled current source) and the second stage (voltage follower), where the resistance is very high. This allows a parallel resonance LC tank to be connected to the additional op amp correction pin. The main advantage of this new configurations is the insignificant influence of the load over the parameters of the circuit (voltage gain, Q-factor, etc.). Some recommendations for designing this kind of analogue circuit are given, based on simulation results, symbol analysis of the transfer function and physical experiments as well as elements’ values calculation using centre frequency, voltage gain, bandwidth and Q-factor of the LC amplifiers as input parameters.     

光子晶体及其应用

光子晶体是一种具有光子带隙的新型功能材料,它独特的物理性质使得光子晶体具有理论研究价值和广泛的应用前景。主要介绍了光子晶体的基本概念和三维光子晶体的制备技术。并综述了光子晶体的一些物理特性及其在光学、通信、微波方面的应用。     

二维Kagome格子光子晶体禁带的数值模拟

采用平面波展开法模拟计算了由空气背景中的介质柱构成的二维Kagome格子光子晶体的能带结构，得到了使完全光子禁带最大化的结构参量．计算结果表明：由圆形、正六边形和正四边形三种不同形状锗介质柱构成的Kagome格子光子晶体都出现了完全光子禁带，最大禁带分别为△=0．014(ωa／2πc)、△=0．013(ωa／2πc)、△=0．011(ωa／2πc)．发现由圆形和正六边形两种介质柱构成的Kagome格子光子晶体在填充比连续变化的较大的范围内都有宽度较为稳定的完全禁带，且它们具有非常相似的能带结构．     

光子带隙型光子晶体光纤

光子晶体光纤（PCF）有着许多奇异的特点和广泛的应用前景。目前,光子晶体光纤的技术发展很快,其潜在应用不断被发掘出来。文章简要分析了光子带隙（PBG）型PCF的导光机制,介绍了它的典型结构、制作工艺和PBG的形成机理。探讨了其在光通信中的应用。     

Extending transmission bandwidth of air-core photonic bandgap fibers

Air-core photonic bandgap fibers offer many unique properties and are critical to many emerging applications. A notable property is the high nonlinear threshold which provides a foundation for applications at high peak powers. The strong interaction of light and air is also essential for a number of emerging applications, especially those based on nonlinear interactions and spectroscopy. For many of those applications, much wider transmission bandwidths are desired to accommodate a wider tuning range or the large number of optical wavelengths involved. Presently, air-core photonic bandgap fibers have a cladding of hexagonal lattice. The densely packed geometry of hexagonal stacking does not allow large nodes in the cladding, which would provide a further increase of photonic bandgaps. On the other hand, a photonic cladding with a square lattice can potentially provide much larger nodes and consequently wider bandgap. In this work, the potentials of much wider bandgap with square lattice cladding is theoretically studied and experimentally demonstrated.     

光子带隙结构在微带带通滤波器中的应用

介绍了两种带有一维光子带隙(Photonic Bandgap，简称PBG)结构的馓带带通滤波器。它们具有良好的慢波滞阻特性，同时在结构上又无须腐蚀接地板．而仅仅修改微带线的形状。计算仿真与测量结果基本相符合。     

分层手征介质的光子带隙特性

导出了分层手征介质中的斜入射电磁波的传输矩阵,由传输矩阵可以计算分层手征介质的反射和透射系数,研究了由手征介质构成的一维周期结构的光子带隙特性及其与入射角的变化关系,讨论了光子带隙与手征导纳之间的关系.研究表明,手征导纳可以控制光子带隙的特性,在适当的参数条件下,可以获得非常理想的多通道滤波特性.     

光子晶体光纤的原理及其应用的研究

光子晶体光纤具有与传统光纤完全不同的几何结构、导光机制、模式特性、色散以及双折射性质。本文简述了光子晶体光纤的一些重要特性及其应用。     

PBG结构在微波领域的应用

20世纪80年代末出现的光子晶体是一种具有光子带隙的新材料,其特有的性质使得光子晶体具有广泛的应用前景。本文介绍了光子晶体的概念,综述了光子带隙结构在微波领域的典型应用和研究进展。     

一种新型微带光子带隙结构的优化设计

本文对一种渐变尺寸的新型光子带隙结构进行了优化设计。根据优化后得出的最优结构参数 ,设计出PBG结构。实验结果证明 ,这种优化后的新型结构可以在保持阻带抑制幅度的同时减小通带内的波纹     

四方格子全固光子带隙光纤带隙特性研究

基于平面波展开法,对四方格子全固光子带隙光纤带隙随结构的变化特性进行了数值模拟,并与具有相同结构参数三角格子全固光子带隙光纤进行了比较,数值结果表明带隙的位置由高折射率棒的结构参数决定,而与高折射率棒的排列方式和棒之间的间距无关,这一结果与反谐振效应非常吻合。最后对理想和实际拉制出的四方格子的全固态光子带隙光纤的带隙进行了比较,得出了在设计光纤时,应利用较低的带隙的结论。     

FDTD方法分析光子带隙微带结构

本文采用时域有限差分法分析计算了一维光子带隙微带结构的S参数,并设计制作了光子带隙（PBG）微带线,进行了测量。将计算结果与测量结果对比可以看出两者吻合得比较好,说明采用的分析方法是有效的。     

一种新型的分段曲率补偿带隙基准源设计

针对传统的带隙基准源曲率补偿效果较差的问题,采用两路跨导放大器设计了一种新型的分段曲率补偿的带隙基准源。其中一路跨导放大器比较三极管的发射极-基极电压VEB和一个粗略的基准电压,在低温段产生随温度升高近似成指数减小的电流;另一路跨导放大器比较VEB和另一个粗略的基准电压,在高温段产生随温度升高近似成指数增大的电流,对传统的电流型带隙基准源进行精确的分段曲率补偿。基于TSMC 0. 18μm CMOS工艺,对电路进行设计和仿真。仿真结果表明,3. 3 V电源电压时,在-40～+150℃温度范围内,温度系数为1. 84×10^-6/℃,低频时的电源抑制比为-98. 3 d B,线性调整率为0. 0047%。     

Acrylate‐Based Photopolymer for Two‐Photon Microfabrication and Photonic Applications

This paper provides a photopolymerizing material suitable for stereolithography of complex submicrometer‐sized three‐dimensional (3D) structural elements to a broad scientific public. Here, we present the formulation of a polymer (LN1 resin) that allows further research in the field of nanofabrication and ‐technology as it surpasses current material limitations. The polymer consists of multifunctional acrylate oligomers as binder, polyfunctional monomers, and a photoinitiator (PI). The chemistry to form 3D structures is based on photopolymerization of the acrylate system initiated by free‐radical species that are triggered by two‐photon absorption of a PI. Important parameters of photocuring, such as the effects of PI concentration, temperature, and light intensity, were studied using photocalorimetry. The thermal stability of the material was tested using thermal gravimetric analysis, providing key information for electronic and photonic applications. Photonic‐crystal structures generated from this resin exhibiting photonic stop gaps in near‐infrared‐ and telecommunication‐wavelength regions are presented.     

Recent progress in microstructured polymer optical fibre fabrication and characterisation

Recent progress in microstructured polymer optical fibre fabrication and characterisation will be presented. A wide range of different optical functionalities can now be obtained by modifications of the microstructure, as is demonstrated by the fibres presented here. Microstructured fibres that are single-mode, highly birefringent or show twin-core coupling are described, in addition to graded-index microstructured fibres and hollow core fibres, the latter case being where light is guided in an air core. Microstructured polymer optical fibres are an exciting new development, offering opportunities to develop fibres for a wide range of applications in telecommunications and optical sensing.     

一种新型光子晶体结构的微带天线

提出了一种新型的基于二维光子晶体基底的微带天线,光子晶体结构是人造的周期性电介质结构,本文采用的方法是在电介质中引入周期性分布的空气孔洞,孔洞的分布是三角形点阵,然后在中心孔洞引入缺陷,但只是在中心孔洞的下半部分引入缺陷,即中心孔洞的深度为周围孔洞深度的一半,天线的贴片放在孔洞的底部,即将天线贴片放在了光子晶体内部。我们采用HFSS仿真软件对该结构进行了模拟,数值仿真结果表明该结构对天线的方向性有明显改善。     

High power ytterbium fiber lasers at extremely long wavelengths by photonic bandgap fiber technology

Yb-doped fiber laser operating at the long-wavelength edge (1150–1200 nm) of the broad gain spectrum has been investigated for yellow-orange sources. Power scaling in this region has been recently achieved by Yb-doped solid-core photonic bandgap fibers, in which the Yb gain profile is engineered by the sharp-cut, bandpass distributed filtering and therefore amplified spontaneous emission in the high-gain region (1030–1100 nm) is strictly inhibited. We have recently demonstrated amplification with as high as 167 W output power and 61% slope efficiency at 1178 nm. The novel gain profiling technique by photonic bandgap fibers can be extended to other rare-earth doped fibers.     

Modification of the Natural Photonic Bandgap of Synthetic Opals via Infilling with Crystalline InP

The growth of high‐quality stoichiometric indium phosphide by atmospheric pressure metal–organic chemical vapor deposition within thin‐film artificial opals has been optimized. The optical properties of these systems have been studied as a function of the filling fraction. A consistent behavior has been found which substantially differs from that of other common infilled opals. The evolution of the InP morphology seems to be strongly correlated with this anomalous photonic response. At the first infiltration stages, the growth leads to the formation of nanocrystallites that eventually, as the infiltration increases, coalesce in single‐crystalline grains of increasing size. The possibility to oxidize the material adds to its potential as a useful optical material.     

平面型金属-电介质光子带隙结构的表面电磁波传输特性

研究了一种平面型金属—电介质光子带隙结构的表面电磁波传输特性。该材料利用常规的印刷电路板技术制作．其金属单元的平面斑图(pattern)分别为六角形和方形两种，空间层状结构为二层与三层两种。在1—20GHz范围内对TE表面波传输情况进行了测试，观察到了TE表面波的能隙结构。不同结构的测试结果表明，三层结构的材料具有较低的禁带中心频率。用局域电感—电容模型定型解释了本文的实验结果。     

光子晶体带隙法在溶液浓度测量中的应用

本文从光子晶体带隙理论出发,分析了相对带隙宽度与测量溶液浓度的之间的对应关系,提出了采用光子晶体平面波展开法测定牛奶浓度的新方案。通过研究以硅半导体材料为背景介质周期性排列空气孔圆柱构成的光子晶体,发现在高频率区域,二维三角晶格结构各向同性光子晶体的光子带隙随待测溶液百分浓度不同而单调变化的。这对浓度测量和高血糖患者的临床应用有一定的指导作用。