抗冲击高绝缘电阻平面光窗金属外壳的研制

采用独特的结构设计,利用高频熔封工艺制作出了抗冲击管帽,并通过选材、优化工艺、改进模具等手段制作了高绝缘电阻管座.实验结果显示,采用以上方法制作的平面光窗外壳能承受3×9.806 N的机械冲击,绝缘电阻达到1×1012Ω,较常规的外壳提高了2～3个数量级.     

光窗的铟锡合金真空焊接工艺研究

采用真空炉对铟锡合金焊料的焊接技术及在光电光窗封装外壳中的应用进行研究分析。根据光电外壳气密性封装要求,设计了完整的蓝宝石-可伐光窗真空焊接工艺方法和流程。通过大量实验得出了优化的焊接工艺曲线(包括温度、时间、气氛和压强等),讨论了封接表面质量、压块重量、焊料厚度对焊接质量的影响。对采用InSn48合金焊料焊接的蓝宝石-可伐光窗管帽按GJB548B-2005中方法1010.1试验条件A、方法2002.1试验条件E分别进行了温度循环、机械冲击考核,气密性能很好地满足相关要求。该研究在光学镀膜层耐温低的光窗封接领域有潜在的应用价值。     

光窗封接工艺对光电外壳抗强冲击影响的研究

通过对三种光窗封接工艺的对比分析,探索了怎样提高带光窗光电外壳的抗强冲击能力。运用有限元软件ANSYS分析MBCY009-W8W的局部封接工艺、高温封接工艺、低温钎焊工艺及其存在微裂纹对抗强冲击能力的影响。按GJB548B-2005方法 2002.1对样品进行机械冲击试验,结果表明低温钎焊工艺很好地满足抗强冲击的要求,研究在有强冲击载荷要求的光窗封接上有潜在的应用价值。     

三种光电外壳光窗封接工艺的强度对比分析

从理论上分析了带光窗外壳的三种制作方式在成型变形上的不同,并对各自进行了强冲击应力模拟分析,最后通过锤击试验对理论分析进行验证,实验结果与结论分析一致,得出金属钎焊管帽抵抗外力的效果最好,高温管帽次之,高频管帽相对较差.     

胶层厚度对多点支撑光窗面形的影响

以某型战斗机光雷保护罩采用的多点支撑光窗为研究对象,建立胶层连接的多点边缘支撑结构模型,通过仿真分析胶层厚度对多点边缘支撑光窗面型的影响。建立“压块-胶层-光窗”有限元分析模型,在结构航向过载、航向随机振动、高低温冲击情况下,对不同胶层厚度仿真结果数据处理,分析胶层厚度对光窗面形变形的影响。结果可知:胶层在0.1~0.5 mm范围内,光窗表面PV值与RMS值,在过载冲击与随机振动仿真试验中,随着胶层厚度的增加呈现先减小后增加的趋势;在温度冲击仿真中,呈现逐渐减小的趋势。     

用电镀法制造硅靶铜导电帽的研究

具有导电帽的硅靶视像管可以减小其惰性,并提高其抗晕光的能力。本文着重对用电镀法制造硅靶铜导电帽的有关问题如:电镀液的组成;电镀槽、电极结构;电流;硅靶表面等诸因素对铜导电帽质量的影响进行了分析。结果表明用电镀法制备硅靶导电帽是一种成本低、无毒害、无污染的简便易行的方法。     

玻璃——金属全气密性封接研究

本文简述了玻璃——金属全气密性高频熔封技术。该技术具有工艺简单、成本低、气密性好、透过率、热稳定性优异等,适合作半导体光电器件光窗帽,也适合于批量生产。     

光学探测系统电磁屏蔽设计与应用

光学探测系统在高功率微波系统运行造成的强辐射、强电磁干扰环境下工作,HPM产生的强电磁脉冲会通过后门耦合的方式由探测器前端光学镜头进入内部的电路系统造成光学探测系统瞬间黑屏、图像抖动、器件毁坏等现象,通过采用光学玻璃金属丝夹层的方法研制光窗,在2.4 GHz±100 MHz频段内电磁屏蔽性能达到了65 dB,同时满足探测目标的光窗透过率的要求。经过应用后表明:加载了这种电磁屏蔽光窗的光学探测系统在HPM工作时图像稳定,未受到干扰。     

基于遗传算法和等效电路模型的窄带通频率选择表面光窗设计方法

提出了一种窄带通频率选择光窗的快速设计方法,该方法结合遗传算法和等效电路模型,能快速准确地给出特定设计目标下光窗的结构参数。该光窗由石英玻璃及镀制在玻璃上下表面的亚波长的金属网栅构成。利用上述方法,可以在几十秒内直接优化出光窗在特定设计目标下的结构参数。与全波仿真相比较,正入射下等效电路模型的准确度高于93%。利用上述方法对光窗的结构参数进行优化,实现了通带透过系数损失小于1.5dB、带外抑制大于20dB、品质因子高于26的性能,同时光窗保持一定的可见光透过率且具有极化不敏感性。结果表明,该方法能快速有效地设计窄带通频率选择光窗。     

塑封隧道结脉冲半导体激光器的研制

报道了一种新型塑料封装隧道结脉冲半导体激光器.采用MOCVD生长了隧道结串联双叠层激光器材料.激光器芯片为标准宽发射区结构.采用塑封结构,在脉冲宽度小于500ns,重复频率小于8kHz工作条件下,其输出光功率斜率效率达到1.7W/A, 是标准单芯片的1.7倍.采用塑封结构,克服了金属封装玻璃光窗在受冲击时易碎的弱点,其抗冲击达到20kg以上,且封装成本低廉.     

Comparative analysis of cumulative distribution function for TCP congestion window size and triple‐duplicate period

Various version of Transmission Control Protocol (TCP) congestion window model are available in the literature. TCP congestion control is handled in two phases: (a) slow start and (b) congestion avoidance. This paper deals with congestion avoidance phase that is based on additive increase multiplicative decrease (AIMD) mechanism in which window size either increase by one or cuts to half of the previous window size. For distribution of window sizes, a model developed by Yan et al has been presented for two loss indications: (a) triple duplicate (TD) and (b) time‐outs (TOs) only while it does not deal with the window size limitation. It does not allow to cap over the TCP congestion window size if the buffer size is restricted to a fixed value though window size could not move beyond that. The unconstrained window size moves on in the presence of low loss probability. In this paper, we propose a model for the case where the window size is bounded by a maximum value that makes applicable to window size limitation as well. Further, the work has been extended to develop a new model that obtains a cumulative distribution function for TD periods (TDPs). The proposed model is validated on ns‐2, and we conclude that observed results for distribution function are very closed to our proposed model.     

Parasitic source and drain resistance in high-electron-mobility transistors

The parasitic source and drain resistances of a high-electron-mobility transistor were analyzed in terms of a two layer transmission line model. The analysis showed that a highly conductive cap layer can function as an extension of the alloyed contact provided that tunneling between the cap layer and the channel is significant. The tunneling between the cap layer and the channel was analyzed in terms of a thermionic-field emission model in which a one dimensional time-dependent WKB transmission probability for the barrier was considered as well as Maxwell-Boltzman statistics for the tunneling carrier distribution. The GaAs cap, GaAlAs layer and 2-DEG channel can then be treated as a distributed resistance element with a characteristic coupling length. A reduction of the parasitic resistance can be obtained for a device structure with a short characteristic coupling length even if there exists an ideal alloyed contact to the 2-DEG channel. A multilayer cap consisting of an undoped GaAs layer inserted between the n-type GaAs and n-type GaAlAs is also proposed to reduce the barrier height for tunneling between the cap layer and the channel. The multilayer cap structure is predicted to appreciably reduce the parasitic resistance at room temperature and still be effective at 77 K.     

Low threshold room temperature pulsed and -57°C CW operationsof 1.3 μm GaInAsP/InP circular planar buried heterostructuresurface-emitting lasers

Room temperature pulsed lasing operation of a 1.3-μm GaInAsP/InP vertical-cavity surface-emitting laser has been achieved by using an effective carrier confinement of circular planar buried heterostructure (CPBH) and high reflectivity SiO₂/Si dielectric multilayer mirrors. The threshold current for a device having a nearly 12-μm-diameter active region was 34 mA at 24°C under pulsed operation. The optimized window cap structure reduces the series resistance to 6~15 Ω. Continuous wave lasing was also obtained up to -57°C, and the threshold below -61°C was still lower than 22 mA     

THz输能窗及天线一体化结构的研究

提出了一种THz输能窗及天线一体化结构,并利用三维电磁仿真软件对其进行模拟计算。计算结果表明这种结构在0.20 THz～0.24 THz范围内的驻波比小于1.5,而所需蓝宝石窗片厚度为0.3 mm,是已知盒型窗窗片厚度的在2倍。这表明在相同工艺条件下,这种结构可以工作在相同厚度窗片盒形窗的2倍工作频率。此外,这种结构还集成了小型天线,减少了太赫兹源的外围波导系统,方便了使用。     

低温光学用杜瓦柔性外壳结构热力特性研究

为了满足低温光学系统低背景、低功耗和红外探测器制冷组件高环境适应性的要求,提出了探测器制冷组件杜瓦主体（窗口、窗口帽和引线盘） 200 K低温保持,与制冷机膨胀机或脉管散热面柔性绝热连接的设计思想。针对低温光学用杜瓦柔性外壳工程应用中的特点,文中以某低温光学用长波12.5 μm 2 000元红外探测器杜瓦组件以例,提出了波纹管作为绝热连接的柔性外壳,重点阐述杜瓦柔性波纹管隔热、力学和相关漏热的设计,并开展不同热负载条件下波纹管热特性验证,可实现最小温度梯度为37.22 K,绝热热阻为1142 K/W,误差在37%。为综合评价低温光学用柔性外壳结构杜瓦组件的性能,对某低温光学用长波12.5 μm 2 000元探测器柔性外壳杜瓦组件开展热真空和鉴定级的力学试验考核验证,试验结果表明实现了200 K低温窗口,探测器60 K工作,杜瓦漏热为544 mW,低温工况工作时相对于常温工况制冷机的功耗下降了53%,并通过了4 g的随机力学考核,验证了低温光学用杜瓦柔性波纹管外壳模型合理可行,对于后续低温光学用杜瓦柔性外壳结构工程应用提供了重要参考。     

Source resistance reduction of AlGaN-GaN HFETs with novel superlattice cap layer

We have developed a novel AlGaN-GaN heterojunction field effect transistor (HFET) with an ultralow source resistance by employing the novel superlattice (SL) cap structure. The particular advantage of the SL cap, i.e., the existence of multiple layers of the polarization-induced two-dimensional electron gas (2DEG) with high mobility and high concentration at each AlGaN-GaN interface, is fully exploited for lowering the lateral resistance and the potential barrier at the interface of the SL cap and the HFET barrier layer. By designing the AlGaN-GaN thickness ratio, we have established a method to obtain the optimized SL structure and have achieved an extremely low source resistance of 0.4 /spl Omega//spl middot/mm which is lower not only than HFETs with the conventional structure but also than those with the n-GaN cap structure. The SL cap HFET fabricated on a sapphire substrate exhibited excellent dc and RF performance, i.e., maximum transconductance of over 400 mS/mm, maximum drain current of 1.2 A/mm, a cutoff frequency of 60 GHz, a maximum frequency of oscillation of 140 GHz, and a very low noise figure minimum of 0.7 dB at 12 GHz.     

Characterizing the layer properties of AlGaAs/GaAs heteroface solar cell structures by specular spectral reflectance

A cheap and non-destructive method for characterizing wafers prior to, during, and after processing is presented. This method is based on optical reflectance measurements. Its application to AlGaAs/GaAs heteroface solar cell structures allows the determination of the thickness of both the cap and window layers, the aluminum composition (even if it is graded) of the window layer and both the thickness and composition of surface oxide (if any). The feasibility of the procedure and method here presented is demonstrated by applying it to two kinds of structures grown by MOCVD (metal organic chemical vapor deposition) and LPE (liquid phase epitaxy). The results obtained are validated experimentally by SIMS and Raman. Finally, the influence of several calculation parameters on the final result is analyzed.     

光学窗口的抗振结构优化分析

作为航空侦察设备中的重要组成部分,光学窗口材料昂贵,加工周期长,而其工作环境非常恶劣,所以如何提高其环境适应性就显得尤为重要。据统计,振动是其失效的主要原因。本文以某工程项目中使用的试验窗口为例,以提高抗振能力为目的,通过理论分析,找出其改善措施,然后通过Ansys Workbench进行有限元仿真,最终得出的分析结果及半实物仿真试验均验证了此措施的可行性。     

Structural and Chemical Comparison of Graphite and BN/AlN Caps Used for Annealing Ion Implanted SiC

The effectiveness of AlN/BN and graphite annealing caps for ion implanted SiC was examined morphologically, structurally, chemically, and electrically. The AlN/BN cap more effectively blocks the out-diffusion of silicon because it is essentially inert. Relatively small amounts of silicon from the SiC diffuse out into the graphite cap and react with it. This has the effect of lowering the Si vapor pressure so that it does not create blow holes in this relatively weak structure. The graphite cap can be removed easily with an oxygen plasma, while warm KOH has to be used to remove the nitride cap, and not all of it can be removed after an 1800°C anneal. The out-diffusion of silicon through the graphite cap is most severe at 1800°C, where it roughens the SiC surface and forms reaction products when the Si reacts with the graphite at a significant rate. At lower temperatures these reaction products form small particulates on the surface that are visible only at higher magnifications. In those regions where the graphite cap crystallized, isolated morphological damage on the SiC surface was also detected, appearing to be in the vicinity of the grain boundaries. Scratches on the substrate surface were not affected even at temperatures as high as 1800°C.     

X波段速调管功率合成输出结构研究(TE01模输出窗设计)

在对X波段高峰值功率微波源迫切需求的牵引下,该文为X波段高峰值功率速调管功率合成输出结构设计了一个工作在9GHz的TE01模输出窗,输出窗相对带宽大于7%,通带内插入驻波比小于1.2.此外,该文还建立了TE01模输出窗窗片稳态温度分布的计算方法.理论分析表明,该输出窗传输50MW的高峰值功率不会由于温升而出现窗片的破裂.