一种基于Nd:GdVO4/PPMgLN的蓝光激光器

利用准相位匹配周期极化掺杂氧化镁(MgO)的铌酸锂(PPMgLN)晶体作为倍频晶体,在晶体最佳工作温度(25℃)时,当作为泵浦源的激光二极管的泵浦激光功率达到4.8W,输出得到了456nm的连续蓝光,最大输出功率为240mW,光光转换效率为5%。倍频晶体PPMgLN的尺寸为3×3×3mm3,极化周期为4.2μm。在此实验的基础上,制成了一台小型全固态456nm连续蓝光激光器。     

紧凑高效的Nd:YVO_4/PPMgLN腔内倍频3.8W连续绿光激光器

研究了一种基于周期极化掺镁铌酸锂(PPMgLN)晶体做倍频器件的新型、紧凑和高功率连续绿光激光器。利用外加电场极化法成功制备了厚度为1 mm,短周期为6.95μm,占空比接近50%,大面积均匀的PPMgLN;在6.8 W单管激光二极管(LD)抽运的情况下,利用通光长度仅1 mm的PPMgLN,腔内倍频获得了3.8 W的绿光532 nm激光输出,光-光转换效率高达56%。     

紧凑型连续波半导体激光倍频的488nm蓝光激光器

利用波导型准相位匹配周期极化反转铌酸锂(PPLN)晶体直接倍频波长为976nm的连续半导体激光二极管,在 接近室温的晶体工作温度(28℃)下,获得了488nm的连续蓝光输出,最大输出大于20mW。所用的晶体尺寸为8mm× 1．4mm×1mm,波导截面为4．5μm×3．5μm,极化周期为5．2μm。研究了波导型PPLN晶体的倍频效率与温度的关系。     

光纤激光器泵浦PPKTP晶体倍频连续绿光输出

用离子交换法降低了磷酸氧钛钾(KTP)晶体的电导率,用高压电场极化反转成功获得了体积为4mm×6mm×1mm,周期为Λ=9.0μm的周期极化KTP(PPKTP)晶体。在倍频(SHG)光学系统中用包层泵浦的光纤激光器输出的1064nm激光作为泵浦光,在室温下得到PPKTP器件的最高SHG转换效率为0.32%,归一化SHG效率为2 4%。化学蚀刻表面显示这种方法获得的PPKTP晶体反转畴边缘整齐,没有明显的畴壁扩展现象。     

周期极化铌酸锂绿光倍频器的研究

利用外加电场的方式，在0.5mm厚的z切铌酸锂晶体中实现了周期性极化反转，基频光波波长为1.064μm，功率为1.75W，在20℃的室温下，得到波长为0.532μm，输出功率为0.9mW的连续倍频绿光输出，倍频转换效率为0.052%。     

基于周期性极化钽酸锂晶体的连续激光倍频技术研究

针对连续激光倍频的需求,对比分析了周期性极化钽酸锂晶体和铌酸锂晶体的非线性光学特性,从技术研究角度确定了周期性极化钽酸锂晶体更适合用于连续激光倍频。依据非线性转换效率和晶体结构安装尺寸,确定了基频激光压缩及倍频激光准直的参数,从保证工程应用的角度选择了81μm极化周期的钽酸锂晶体,设计并实现了双光路倍频,获得了超过5W的540nm连续倍频激光输出。     

2.1 W连续绿光输出的一阶准相位匹配内腔倍频

利用周期极化化学计量比掺氧化镁LiTaO3晶体(PP-MgO∶SLT),对半导体激光器(LD)端面抽运的1064-nm-Nd∶YVO4激光器进行了一阶准相位匹配(QPM)内腔倍频(ISHG)。PP-MgO∶SLT晶体长20 mm,极化周期为7.93μm(室温下),利用外加电场极化法制作,极化沿晶体的z向进行。实验中基频光波和倍频光波均沿晶体z向偏振以利用其最大的有效非线性系数。Nd∶YVO4激光器选用三镜折叠腔结构,在半导体激光器抽运功率为11 W,晶体温度为70.4℃时,产生了最大输出功率为2.1 W的连续绿光激光,光-光转换效率为19%。同时对PP-MgO∶SLT晶体外腔单程倍频下的转换效率与晶体温度间的关系进行了理论研究。实验中测得的内腔倍频的允许温度要远大于外腔单程倍频;另外,观察到随着晶体温度的变化倍频光功率出现突然下降的现象,并给出了相应的讨论。     

高掺镁铌酸锂晶体周期极化及倍频特性研究

研究了掺镁(5mol％)铌酸锂晶体的周期极化特性,发现晶体的极化矫顽场仅为3kV／mm,根据镁掺杂对晶体本征缺陷的影响解释了极化矫顽场降低的原因．采用短脉冲极化电场,对极化电流的热效应进行抑制从而消除了晶体均匀性对制备周期极化光栅的影响,在1mm厚的掺镁(5mol％)铌酸锂晶体上成功制备出了均匀的周期极化光栅．在室温下,利用1．064μm的Nd：YAG调Q激光器对得到的周期极化掺镁铌酸锂晶体进行了倍频实验,在输入功率为75mW时,得到3．5mW的532nm倍频绿光输出,转换效率为4．6％．     

双棒串接、声光调Q Nd:YAG激光器

在计算谐振腔稳定参数(A+D)/2基础上,采用双捧串接、声光调Q,获得了75W1.06μm准连续激光输出.在此基础上,腔内插入一块8mm×8mm×7mm的高纯KTP晶体,获得了31.1W的倍频绿光输出.     

周期极化钽酸锂倍频窄谱线全光纤连续激光放大器特性

通过准相位匹配技术,采用1μm波段高功率窄谱线连续光纤激光放大器抽运高二次谐波转换效率周期性极化晶体,是实现高光束质量、小型化、高功率连续绿光激光器的一个非常有前途的方向。实验自主研发了高效率主振荡功率放大(MOPA)全光纤保偏放大模块,获得中心波长为1064.25nm,线宽为0.035nm的30 W连续线偏振激光,并以此作为基频光抽运国产周期极化钽酸锂(PPSLT)晶体进行了外腔单通倍频实验。保持PPSLT晶体的控制温度为145.6℃,在抽运光功率为21.5W时得到了2.1W的绿光输出。实验分析了温度、基频光功率密度和Boyd-Kleinman聚焦因子对倍频光转换效率的影响。实验过程中没有出现饱和现象,进一步提高抽运功率有望获得更高功率的绿光。     

聚对苯撑苯并双(口恶)唑发光及其器件制备

采用光谱技术,研究了聚对苯撑苯并双(口恶)唑(PBO)溶液的光敏发光特性,并用相对法估算出溶液发光效率在50%范围.结合光谱技术、半导体电学和电化学等研究手段,具体研究了以PBO为发光层的单层电致发光器件,研究结果显示,电致发光与薄膜的光致发光有具有相同的发光中心,峰值位于510 nm左右.同时发现,由于存制备过程中不同处理条件使得不同厚度薄膜残留的掺杂物质浓度不同,从而引起薄膜的导电性的不同.使得器件的阈值场强随PBO厚度的减小而逐渐增加.     

系统级封装新型埋入式电源滤波结构的研究

在高密度小尺寸的系统级封装(SiP)中,对供电系统的完整性要求越来越高,多芯片共用一个电源网路所产生的电压抖动除了会影响到芯片的正常工作,还会通过供电网路干扰到临近电路和其他敏感电路,导致芯片误动作,以及信号完整性和其他电磁干扰问题.这种电压抖动所占频带相当宽,几百MHz到几个GHz的中频电源噪声普通方法很难去除.结合埋入式电容和电源分割方法的特点,提出一种新型高性能埋入式电源低通滤波结构直接替代电源/地平面.研究表明,在0.65～4GHz的频带内隔离深度可达-40～75 dB,电源阻抗均在0.25ohm以下,实现了宽频高隔离度的高性能滤波作用.分别用电磁场和广义传输线两种仿真器模拟,高频等效电路模型分析这种低通滤波器的工作原理以及结构对隔离性能的影响,并进行了实验验证.     

Emerging interconnects: a state-of-the-art review and emerging solutions

Aluminium was a primary material for interconnection in integrated circuits (ICs) since their inception. Later, copper was introduced as interconnect material which has better metallic conductivity and resistance to electromigration. As the aggressive technology scaling continues, the copper resistivity increased because of size effects, which causes increase in delay, power dissipation and electromigration. The need to reduce the resistor-capacitor??????? delay, dynamic power utilisation and the crosstalk commotion is as of now the fundamental main impetus behind the presentation of new materials. The purpose of this paper is to do a survey of interconnect material used in IC from introduction of ICs to till date. This paper studies and reviews new materials available for interconnect application which are optical interconnects, carbon nanotube (CNT), graphene nanoribbons (GNRs) and silicon nanowires which are alternatives to copper. While doing a survey of interconnect material, it is found that multiwalled CNTs, multilayer GNR and mixed CNT bundles are promising candidates and are ultimate choice that can strongly address the problems faced by copper but on integration basis copper would last for coming years.     

Arsenic deposition as a precursor layer on silicon (211) and (311) surfaces

We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations. It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311) had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy, while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites. This would ensure a nonpolar, B-face growth.     

光子晶体微腔发光二极管

光子晶体微腔因其具有增强自发辐射、定向输出和单模工作的能力而受到广泛关注。介绍了光子晶体微腔发光二极管的基本原理、设计、特性、制作及其典型器件。     

Comparative study of maximum power point tracking techniques for hybrid renewable energy system

The power generation demand is increasing day-by-day throughout the world, therefore, the use of hybrid systems becomes a significant solution. The hybrid renewable energy system (HRES) is used for delivering power in various regions in order to overcome intermittence of wind and solar resources. Because of increasing environmental problems, for example, greenhouse gas emission and energy cost have interested novel research into substitute methods in favour of electrical power generation. Maximum Power Point Tracking (MPPT) control method is a vast deal of novel research used for enhancing the efficiency of HRES. The authors have revealed that the hybrid techniques i.e. Global MPPT, fuzzy-neuro systems, Adaptive Neuro-Fuzzy Inference System (ANFIS), Perturbed and Observe (P&O) + Adaptive Neural Network (ANN) etc. can provide best results as compared to other MPPT control methods. This paper offering a state of art review of MPPT control techniques for HRES.     

用于单光子TOF测量的时间-幅度变换器

基于新型共源共栅电流源的积分方法,设计了一种用于单光子飞行时间(TOF)测量的时间-幅度变换器(TAC)。该方法有效简化了TAC电路结构,减小了TAC占用面积,显著提高了TOF的满量程范围(FSR)。采用0.18 μm标准CMOS工艺设计。集成TAC的单光子探测器像素单元的填充因子可达到26.8%。后仿真结果表明,该TAC在120 ns的FSR内具有230 ps的定时分辨率,微分非线性(DNL)低于0.05 LSB,积分非线性(INL)低于1.1 LSB。蒙特卡洛仿真表明,512个TAC像素间的不均匀性低于0.5 %。该TAC非常适用于高密度时间相关的单光子计数(TCSPC)探测器阵列。     

Joint estimation of TOA and DOA in IR-UWB system using a successive propagator method

Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm.     

多孔硅发光机制的分析

从量子力学的基本理论出发讨论了量子限制效应，推导出多孔硅有效禁带宽度增量并用量子限制效应和表面态及其物质在发光中作用的理论解释了ＰＳ光致发光的实验现象。     

一种基于分段CRC的LDPC译码的改进算法

级联多个循环冗余校验(CRC)的LDPC译码算法有效地改善了译码的收敛特性。然而在其译码算法中,当CRC检测的整体漏检概率不够低时,出现误码平台。因此,该文提出了改进算法,通过减少在译码算法中CRC检测的次数,降低整体漏检概率,提高了误码性能。仿真表明改进的算法提高了误码性能,译码复杂度也增加不大。