基于腔结构的射频微机械谐振元件的设计

对圆柱形复合腔结构微机械谐振元件进行了设计研究,提出了一种基于柱形腔结构的微机械复合谐振元件的设计方法,并对其结构及特性进行了研究.建立了复合腔结构的电磁场数学方程,腔体基于体微机械微细加工技术实现工艺设计,最后对该元件进行了仿真分析.TM010模式下,谐振腔谐振频率为24.313299GHz,Q值为3529.707890,考虑微带耦合时仿真出复合谐振元件的最佳谐振频率为24.75GHz.仿真实验结果和理论值的平均误差不到1%,两者吻合得很好,说明了该设计的可行性.进一步改变结构参数,可获取不同谐振频率的器件,且可在腔体中填充高介电常数介质来减小器件的谐振频率,克服了以往使用腔体结构在低频段时体积过大等问题.     

基于Cantor结构的一维光子晶体耦合腔的光学特性

在N=3的三分Cantor多层结构的基础上设计了一种光子晶体耦合腔结构,用传输矩阵法研究了这种耦合腔结构的光学特性。结果表明,新结构有更宽的带隙,并在宽带隙中出现了一个损耗非常小的超窄透射窗口;保持缺陷层的几何厚度不变,改变缺陷层介质的折射率,该透射窗口位置能在很大的范围内移动。这种新的耦合腔结构可用作超窄带光子晶体滤波器或波长可调谐滤波器,在光通信超密集波分复用和光学精密测量等领域中有应用价值。     

四通道二维光子晶体解波分复用系统

利用光子晶体环形腔缺陷模与线缺陷波导之间的共振耦合原理,设计了一种由主波导、环形腔和60°弯波导组成的四通道二维三角晶格光子晶体解波分复用系统。通过平面波展开法计算线缺陷波导的能带结构;利用时域有限差分法(FTDT)计算了不同频率的光波在该系统中的传输特性。最后,分析了影响输出效率和品质因子的因素并对该系统进行了改进。分析表明:改变环形腔内介质柱的半径可调节谐振频率,而在主波导末端增加反射介质柱以及改变耦合区域中介质柱的形状可提高各通道的谐振频率光波的透射率。计算结果显示:该系统较好地实现了4个波长的解波分复用,透射率均达90%以上。另外,该系统结构简单,便于加工制造,且体积小,有利于大规模集成。     

液晶F-P腔中的反射相移

采用一种简化的薄膜矩阵方法,引入相移系数N的概念,分析了可调谐液晶Fabry-Perot腔(F-P腔)介质反射镜中心波长附近的反射相移色散对其调谐性能的影响。对文中给出的具体器件参数,在腔长小于5μm时,即约为3倍中心波长(1.55μm)时,受反射相位穿透深度的影响,器件的半峰值全宽(FWHM)急剧变小,自由光谱范围(FSR)将变窄;且腔长越小,影响越大。     

多信道二维光子晶体滤波器

根据光波模在光子晶体线缺陷波导和环形谐振腔之间的耦合原理,在二维三角晶格光子晶体中设计了一款由线缺陷主波导、环形谐振腔、60°弯下载波导组成的多信道下载滤波器。利用平面波展开方法计算了完整光子晶体及线缺陷波导的能带结构;基于时域有限差分方法计算了各目标频率光信号在器件中的传输特性,分析了影响器件耦合效率的因素并对其进行了改进。分析表明:通过改变环形谐振腔内介质柱的半径可以调节光子晶体环形谐振腔的谐振频率,而改变线缺陷主波导与环形谐振腔之间耦合区域中介质柱的形状以及将直下载波导改换成60°弯下载波导可以提高线缺陷主波导、60°弯波导与环形谐振腔之间的耦合效率。计算结果显示:优化后的多信道二维光子晶体滤波器具备优良的选频功能,各目标频率光信号的透射率均达90%以上。与传统半导体介质材料器件相比,该器件体积较小,结构简单,易于大规模集成,很有应用前景。     

基于温控系统的太赫兹可调谐滤波器

集成太赫兹滤波器是实现集成太赫兹通信系统的基本器件之一,为了使太赫兹滤波器实现片上可调,提出了基于温控系统的太赫兹可调谐滤波器。相比于其他的太赫兹滤波器,提出的片上可调谐滤波器的调谐方法简单,尺寸小,可以很好地与其他太赫兹器件集成到晶片上。利用温控系统改变晶片的温度,再利用硅材料的热光效应改变折射率,使得微环耦合状态发生变化,从而让太赫兹滤波器的谐振峰发生漂移。在将加热片从30℃逐渐加温到90℃的过程中,太赫兹可调谐滤波器在180 GHz附近的谐振峰中心频率从180.453 GHz逐渐减小到180.224 GHz,变化范围为0.229 GHz,谐振深度从-68 dB逐渐变化为-44 dB,半高宽由原来的0.040 GHz逐渐变为0.246 GHz。     

金属和介质组合的双半波滤光片的设计和制备

前言用一层金属膜代替全介质双半波滤光片中两间隔层之间的反射膜,组成了介质多层膜|间隔层|金属膜|间隔层|介质多层膜这样的混合结构。这种组合的滤光片中,介质多层膜和间隔层实质上是金属膜的减反射膜,使金属膜对于中心波长λ_0的反射率减至接近于零。因而波长λ_0的透射率可增至80％左右,同时这组减反射膜对波长变化很敏感,稍一偏离中心波长,其减反射特性就减退,使透射率下降,这样使形成了一通带轮廓,在通带的两侧,多层介质膜系增进了金属膜的反射率,因此仍然保持着金属膜的宽反射区。理论计算表明,中心波长的位置,主要决定于两间隔层的厚度,两间隔层厚度的一致性对滤光片的峰值透射率,通带形状和半宽度有     

微机械多层短接式蓝牙天线

集成电路与微机械天线对于基底介质的要求不同,前者需要高介电常数的介质,而后者所需介质的介电常数则较低,要将两者集成到一起存在一定困难.为了满足蓝牙通信器件的需要,以便将微带天线与电路集成在一起,设计了背腔-短接式微带贴片天线,并采用微机械加工工艺制作了样品,其10dB带宽达到了10%以上,辐射效率为67%,长度仅为1/6波长,基本达到了蓝牙通信器件的要求.     

采用微机械加工技术的微光学加速度

表面微机械加工技术是实现单片集成微光学系统的一种新方法。本文介绍一种新型的采用微机械加工技术的微型光学加速度计,包括设计、关键器件的加工和测试,它是基于光线和光闸相互作用引起通光量变化的工作原理。这一微光学加速度计包含一个2μm厚的多晶硅光闸,光闸采用微弹簧支撑在基片上,微弹簧是长度为200μm的多晶硅褶曲梁,硅基片和微结构之间所夹的牺牲层采用氢氟酸湿法刻蚀去除。光闸设计为一个质量弹簧系统,对加速度力产生响应。     

硅基铁电微声学器件中薄膜残余应力的研究

采用基底曲率法测量了硅基铁电微声学器件中各层薄膜的残余应力情况,通过调节热氧化的二氧化硅层的厚度,优化了微声学器件中复合膜的残余应力,得到平整的振膜结构,提高了器件的可靠性和成品率。     

Hybrid microcavity for superminiature single quantum dot based emitters

This paper describes the development and implementation of a microcavity based on a semiconductor Bragg reflector and a microlens selectively positioned over a single (111) InGaAs quantum dot. The structure of the microcavity ensures effective pumping of quantum dots and high external quantum emission output efficiency. This microcavity can be used to create single photon emitters and emitters of entangled photon pairs based on single semiconductor quantum dots.     

二层结构（介质＋金属）节能膜特性分析

本文给出了二层结构(介质+金属)节能膜的反射率与单层金属膜反射率之间的关系,提出二层结构节能膜的反射率存在着极小值,并据此提出了设计二层结构节能膜时确定介质膜折射率和位相厚度的方法。     

单层带通FSS的带内传输损耗机理

阐述了平面波在无限平面单层频率选择表面(FSS)中的带内损耗机理,区分失配损耗和介质损耗,基于模分析法研究了诸多因素对损耗特性的影响.介质有耗时,TE波大入射角下损耗最大;阵列分布或单元缝隙影响带宽的同时,介质损耗与带宽总是呈相反的趋势;单侧介质加载的带内传输损耗主要是由介质损耗还是带内反射所致取决于介质厚度,但任何厚度的介质覆盖均比衬底时的带内反射要小;对称加载时则主要为介质损耗,且低于单侧加载.     

Study of the influence of the dielectric layer thickness in a CNT-FED

An experimental investigation is carried out to study the influences of the dielectric layer thickness variation on the field emission characteristics and luminance distribution in a CNT-FED fabricated by screen-printing. Two steps are contained in the investigation: (1) the dielectric layer thickness fluctuations are presented with an ultrasonic thickness gauge, and (2) a simulation model is constructed to study the corresponding influences of the dielectric layer thickness fluctuations on the field emission characteristics and luminance uniformity on the screen. Our findings indicate that the dielectric layer thickness fluctuations are mainly larger than 5 microm, which mean the dielectric layer thickness fluctuation is an important cause of the non-uniform luminance distribution according to the analysis results from our simulation model. From the simulation results, we also determine the tolerance of the dielectric layer thickness in a CNT-FED to achieve uniform luminance and spot size on the screen.     

微腔对有机发光的影响的研究

利用介质膜反射镜 ,在光泵浦有机小分子薄膜微腔的研究中 ,观察到了谱线窄化、峰值强度增强、方向性集中于腔轴、控制发射波长和荧光寿命的缩短等一系列腔效应。其中用软膜反射镜 ,消除了镀制过程中热辐射对有机发光材料的影响 ,谱线半宽最窄达3.4nm,窄化了 2 5倍 ;峰值强度最大增强了 1 6倍。     

Fabrication of high quality factor lithium niobate double-disk using a femtosecond laser

We demonstrate fabrication of a high-quality factor lithium niobate double-disk whispering-gallery microcavity using femtosecond laser assisted ion beam milling. Using this method, two vertically stacked 30-µm diameter disks with a 200-nm gap are fabricated. With our device, an optical quality factor as high as 1.35?×?10⁵ is demonstrated. Our approach is scalable to fabricate multiple disks on a single chip.     

Thermal analysis of high power LEDs on the MCPCB

The management of the reduced junction temperature of LEDs is a critical issue because it will affect many physical parameters such as light output, wave length and LED’s lifetime. The model used in this simulation consists of a metal core PCB attached with six chips(GaN on sapphire, Ag paste, cathode/anode, silicone encapsulant, mold frame) for 5W LED module. The MCPCB is composed of an aluminum base plate, a thin layer of dielectric, and a layer of copper. The temperature distribution of the developed LED module was simulated, and the thermal behavior within this 3-D model was investigated by using a commercial computational fluid dynamic code (Fluent 6.3). The results showed that the temperature variation along the vertical direction is more dominant than that in the circumferential direction due to the heat spreading effect of the copper layer. The ratio of heat dissipation through the each thermal path was calculated and compared for various input conditions. Several parameters that increase the junction temperature, such as the thermal conductivity and thickness of the dielectric layer and the encapsulate material, heat transfer coefficient and input power were also examined. Finally, a combination of designs for attenuating the junction temperature was proposed.     

Analysis of the Transmission Spectra of Optical Microcavities Using the Mode Broadening Method

This paper presents an algorithm for processing the transmission spectra of whisperinggallery optical microcavities for use as a nanoparticle detector. The algorithm is based on the broadening of the microcavity resonance curve during precipitation of nanoparticles on the microcavity surface. Experimental results on the detection of particles are compared with Langmuir adsorption theory. The contribution of the instability of the excitation radiation source due to the temperature drift of the resonant frequency to the measurement error is estimated.     

The Analysis of Multi-Layer Conductor-Backed Coplanar Waveguide for Moisture Sensor Application

The analysis of conductor-backed coplanar waveguide moisture sensor by using numerical method is described. The effective dielectric constant, characteristic impedance and dielectric loss of this multi-layer structure are calculated at various moisture contents with respect to protective layer thickness. The analysis shows that calculated values are drastically affected by a small thickness of the protective layer. The experimental results of the attenuation of sensor at various moisture contents agree reasonably with the theoretical data based on the above analysis. The information available from this study is important for estimating of the dynamic range and optimal design of the sensor.     

混粉准干式电火花加工试验研究

提出一种混粉准干式电火花加工技术,其加工介质是气液固三相流混合物。试验结果表明,材料去除率与表面粗糙度随脉冲宽度、峰值电流及分层厚度的增大而增大,脉冲间隙作用则相反,提高空气压力既有助于提高材料去除率又可降低表面粗糙度,电极损耗随脉冲宽度增大而减小,当脉冲宽度较大时电极损耗接近于零,随峰值电流增大而增加。由于液滴、粉末的介入,气体介质的绝缘强度降低,放电间隙会增加,有利于电蚀产物的排除,可减少短路、电弧放电的发生率,加工稳定性得到提高,从而材料去除率得到提高;由于粉末会产生放电分散效果,电蚀凹坑深度减小,工件表面粗糙度降低。