自成像列阵共振腔的分析——Ⅰ.Talbot共振腔

利用自成像效应进行半导体列阵激光器锁相是一种重要的外腔锁相技术,所构成的共振腔可分为Talbot腔和带相位补偿板的Lau腔。我们用Fox-Li方法计算了共振模式。本文给出了Talbot腔的计算结果和分析,表明同相和反相模的损耗随腔长变化存在临界点。     

外腔锁相改善半导体激光器列阵输出光束特性

采用一个由快轴准直透镜和一个高反射率平面镜组成的简单外腔,实现了半导体激光器列阵(DLA)锁相运行,改善了DLA的出射光束质量。DLA远场出现了3个瓣,每瓣发散角为10mrad左右;光谱从自由运行时的2 .2nm压缩到了0 .3nm ;阈值电流由7A降低到了5 .5A。     

基于Talbot效应的激光二极管阵列外腔锁相

对基于Talbot效应的激光二极管（LD）阵列外腔锁相进行了理论和实验研究。在腔内各阶超模近场分布的基础上，在腔外加会聚透镜，在其焦平面上得到了同相模和异相模的远场分布。根据同相模和异相模在Talbot腔中的分布特性，提出ZT／2腔（指腔长的往返长度）进行外腔锁相时的理想腔长。由于ZT／2腔内是异相模振荡，远场图像为双瓣模，这时如果让外腔镜在慢轴方向倾斜角度α，让反馈回阵列的同相模和异相模成像位置各发生d／2的偏移，恰好可以选择同相模而抑制异相模。最后采用ZT／2腔对LD阵列的外腔锁相进行了实验研究，并在外腔镜不偏转和偏转角度α时分别观察到同相模和异相模的锁相现象。经过分析计算，同相模锁相时，奠远场单瓣模的发散角约为1.96mrad．     

外腔锁相二极管激光列阵超模的阈值分析

利用耦合矩阵本征值求得了外腔锁相二极管激光列阵的各阶超模所应满足的阈值条件 ,研究了激光器前端面剩余反射和外腔长度对各阶超模阈值增益的影响。在无剩余反射的理想情况下 ,阈值增益曲线随外腔长度变化缓慢 ,从而可以通过选择外腔长度使DLA稳定运行在最高阶或最低阶超模 ;在有剩余反射时 ,外腔长度在波长范围内的变化都可能使DLA在最高阶和最低阶模式之间交替运行     

二极管激光阵列在Talbot外腔锁相中的超模分析

采用数值计算的方法,对二极管激光阵列在Talbot腔、1/2Talbot腔和1/4Talbot腔中锁相时,同相模和异相模的分布进行了计算。结果表明:同相模在Talbot腔中成像位置没改变,在1/2Talbot腔中成像的位置有d/2的偏移,成像均没有产生相移;在1/4Talbot腔中同相模的分布是两组Talbot像的相干叠加,一组成像位置没有改变,产生-π/4的相移,另一组成像位置有d/2的偏移,产生π/4的相移。异相模在Talbot腔和1/2Talbot腔中成像位置均没有改变,在Talbot腔中异相模产生-π/2的相移,而在1/2Talbot腔中产生-π/4的相移;在1/4Talbot腔中异相模也是两组Talbot像的相干叠加,一组成像位置向左偏移d/4 ,一组向右偏移d/4 ,均产生-π/8的相移。所得结果给出了二级管激光阵列在Talbot外腔中同相模和异相模的分布规律。     

提高二极管激光阵列外腔锁相效率的实验研究

采用1/4 Talbot外腔实现宽条二极管激光阵列的锁相,在工作电流是35 A时,获得7.56 W的锁相输出功率,输出光束的远场图像是多瓣结构,锁相前后输出光的光谱宽度从2.0 nm压缩到0.2 nm。腔内插入焦距大约为5倍腔长的柱透镜,在相同电流下获得8.75 W的锁相输出功率,输出光的远场图像是多瓣结构,输出超模的数目有所减少,能量向中部集中,输出光的光谱宽度是0.2 nm。     

高集成度激光列阵的外腔工作参数稳定技术

匹配高系统集成度的半导体二极管激光列阵(DLA)多发光单元特性的高系统集成度外腔工作参数稳定技术,通过拾取外腔形变传感器的响应等运行状态监控参数,经映射处理等处理后,获取控制参数,适时调整基超模运行所需腔体参数等,反馈控制,使DLA稳定运行于基超模.求得系统控制参数与外腔等参数之间的关系,以及建立相应鲁棒控制模型,是随DLA及其应用具体需求设计控制系统的指导基础,实验表明,基于此优化设计的高密外腔形变传感控制系统,可精细传感控制外腔形变,稳定外腔工作参数,改善高集成度激光列阵系统稳定运行于基超模可用性和系统可靠性.     

“smile”对一维分布光源相干合束的影响

利用傅立叶方法导出的相下光束合成的远场表达式,讨论了一维锁相二极管激光列阵的相干合成远场.对发光单元数目分别为5、9、19列阵的同相模的远场光强分布进行了计算.以19个发光单元线阵为例,讨论了存在"smile"时DLA的远场特征,研究表明:"smile"对已经具有相干性的多光束合成场远场光强的分布并无严重的影响.     

外腔锁相中二极管列阵相邻单元间不同侧模的耦合系数

推导了锁相外腔中半导体激光器列阵相邻发光单元之间不同阶侧模的耦合系数,计算了耦合系数的幅度与外腔长度的关系。结果表明:幅度的极大值对应的外腔长度随侧模阶次增大而减小,不同阶次侧模耦合系数的最大幅度也随阶次降低而减小。上述结果意味着;要实现相邻单元间的基侧模耦合锁相,应该把腔长放在对应的极大值附近;同时也预示着如果腔长过短,可能会出现高阶侧模的外腔锁相。     

二极管激光阵列光栅-外腔谱合成系统中光束串扰行为及其对合成效率的影响

在二极管激光阵列(DLA)光栅-外腔谱合成系统中,由于变换透镜像差、光栅制作误差及"smile"工艺误差等因素的综合作用,将导致DLA发光单元间出现光束串扰。通过分析光束串扰行为的产生机理,将主要的光束串扰行为分为两类,即杂散光返回至发光单元自身,以及经外腔反馈到其他单元,进而分别导致自激振荡模式和耦合振荡模式的产生。在此基础上,给出了含串扰光注入的半导体激光器速率方程,进而推导出DLA发光单元的合成效率模型,分析了自激振荡和耦合振荡对发光单元合成效率的影响。结果表明,杂散光返回至发光单元自身,以及经外腔反馈到其他单元这两种光束串扰行为会不同程度地降低合成效率,且后者影响更大。在实际工作中,需要采取措施对光束串扰行为加以抑制。     

Numerical calculation and statistical analysis of MW fieldintensity on synchronized emitters

Usually, there is one MF emitter for an AM station working at one frequency in the metropolis. The authors consider three same-frequency low power AM emitters working on synchronized broadcasting. Previous field measurements in Shanghai have shown that the reception quality of three low power emitters working synchronously was rather better than a single high power emitter. This article proposes the specifications and the statistical rules of a synchronized emitter by means of computer visualization, and presents field intensity maps through calculation, and makes comparisons and analyses the results     

Self-heating in multi-emitter SiGe HBTs

High power bipolar transistors often have multiple emitters, to achieve high currents, and efficient use of the whole emitter area. The emitters experience high current densities and are self-heated above the ambient temperature, leading to concerns about thermal run-away and damage to the device. Here we use a multi-emitter SiGe HBT, with multiple emitter contacts, to examine the temperature distribution in the emitters in such devices. We have measured the temperature increase in different emitters by biasing one emitter at a time and using the other base–emitter junctions as thermometers. We show that use of a selectively implanted collector does not alter the temperature increase or thermal coupling between the emitters.     

Analytical models for the series resistance of selective emitters in silicon solar cells including the effect of busbars

A theoretical analysis of the power loss and series resistance of the front side emitter in silicon solar cells is presented. Existing 1D models (infinitely long finger) and 2D models (including the effect of busbars) of emitter series resistance contribution are extended to the case of selective emitters. The general case of different current densities for both emitters in the selective emitter scheme is considered in these extensions. The resulting models depend on the individual sheet resistances and current densities in both emitters and the device's overall grid geometry. The models are corroborated by finite element simulation of the potential in the emitter. An excellent agreement is found between the analytical models, and the simulations for a wide range of sheet resistances typically encountered in silicon solar cells. Grid simulations using the 2D model are applied to solar cells with selective emitters, where the width of the low‐resistive emitter was varied. The simulations demonstrate that the 2D model can explain the absolute change in fill factor observed in these cells. Copyright © 2013 John Wiley & Sons, Ltd.     

基于808nm半导体激光器单管合束技术的光纤耦合模块

由于单管半导体激光器比半导体激光线阵、叠阵具有更好的光束质量及散热特性,因此更适用于光电干扰光源。针对于电荷耦合器件(CCD)光谱响应曲线特征,采用808nm单管半导体激光器为光源,将24只单管半导体激光器分组集成,通过空间合束和偏振合束以提高其输出功率密度,采用自行设计的光学系统对光束进行扩束聚焦,耦合进芯径为300μm,数值孔径0.22的光纤中,所有激光器都采用串联方式,在8.5A电流下通过光纤输出功率为162W,耦合效率达到84%。     

Silicon heterojunction bipolar transistors with amorphous and microcrystalline emitters

The emitter Gummel number of bipolar transistors with an amorphous silicon emitter-base heterojunction is shown to be very large. The temperature dependence of the common-emitter current gain of such heterojunction bipolar transistors is much smaller than that of conventional homojunction transistors. With the actual technology the applicability of amorphous silicon emitters is limited by the emitter series resistance which is too high for VLSI applications. Microcrystalline silicon is a promising emitter material as it combines the high emitter efficiency of amorphous silicon emitters with a much lower resistivity, yielding lower emitter resistances.     

结合卷积神经网络和随机森林的辐射源个体识别

为提高辐射源个体识别准确度,解决工程化应用问题,同时避免在信号样本有限的情况下单一识别算法的局限性,提出了一种结合卷积神经网络和随机森林的辐射源个体识别方法.该方法分别利用卷积神经网络和随机森林训练生成两组个体识别模型,然后采用识别概率统计法生成不同辐射源个体的综合权值向量,最后根据权重向量形成针对不同辐射源个体的综合...     

锥形与金字塔形场发射尖端电学特性分析

场致电子发射具有高效、响应快等优点,有着广泛的应用前景。锥形和金字塔形尖端是两种常见的场发射尖端结构。主要分析了这两种尖端结构的场发射电学特性,并在此基础上提出了进一步实现结构优化的途径。为此,建立了两种尖端的三维模型,并利用有限元法深入讨论了结构尺寸,包括尖端曲率半径、尖端与阳极间距以及尖端高度对电场分布以及电场强度的影响。结果表明,减小尖端曲率半径、缩短尖端与阳极间距、以及选择适当的锥体高度是优化尖端场致电子发射性能的三个重要途径。在综合考虑电场分布以及电场强度的情况下,可以发现锥形尖端更有利于产生高密度小束径的低能电子束,而金字塔形尖端则更适用于高压力灵敏度的应用需求。     

低轨双星无源探测系统对运动辐射源的快速检测算法

针对时频差体制的低轨圆轨道双星无源探测系统不能对运动辐射源进行定位和辐射源是否运动进行判别问题,提出了一种通过单次观测实现运动辐射源定位与运动性判别的快速算法。该算法利用信号到达角与信号达到时差联合定位结果,结合信号到达频差对平行于大地水准面的匀速运动目标进行运动性检测,使系统在观测量存在误差条件下仍能有效进行目标运动性判别。将其应用到低轨双星无源探测系统中,仿真结果表明算法对速度大于60 m/s以上的辐射源具备优于95%的正确检测概率。     

Integration of screen-printing and rapid thermal processingtechnologies for silicon solar cell fabrication

For the first time, the potentially cost-effective technologies of rapid thermal processing (RTP) and screen-printing (SP) have been combined into a single process sequence to achieve solar cell efficiencies as high as 14.7% on 0.2 Ω-cm FZ and 14.8% on 3 Ω-cm Cz silicon. These results were achieved without application of a nonhomogeneous (selective) emitter, texturing, or oxide passivation. By tailoring the RTP thermal cycles for emitter diffusion and firing of the screen-printed silver contacts, fill factor values >0.79 were realized on emitters with a sheet resistance (ρ_s ) of ~20 Ω/□ and grid shading <6%. Such high fill factors clearly demonstrate that screen-printed contacts can be fired on extremely shallow RTP emitters (x_j=0.25-0.3 μm) without shunting cells. IQE analysis depicts a strong preference for shallow emitter junction depths to achieve optimal short wavelength response of these unpassivated emitters. In some cases, front contacts were printed through plasma enhanced chemical vapor deposited (PECVD) SiN/SiO₂ dielectrics which prevented the shunting of shallow emitters by serving as partial barriers minimizing the diffusion of metallic species from the contacts. The firing of screen-printed contacts through these PECVD films, achieved the multiple purposes of contact formation, efficient front surface passivation due to annealing of the SiN, and high quality antireflection (AR). Research is presently underway to further optimize the RTP emitter design for screen-printing and develop techniques for implementing selective emitter and oxide passivation technologies for higher efficiency cells     

Degradation mechanism study and electron scattering device structure for long lifetime in blue phosphorescent organic light-emitting diodes

Degradation of Ir based blue phosphorescent emitters was analyzed from the viewpoint of triplet-polaron annihilation (TPA) of the emitters. Two different classes of Ir emitters, F substituted phenylpyridine type Ir emitter and F substituted phenylimidazole type Ir emitter, were compared as the blue emitters. Aging test of singlet carrier devices of the Ir emitters under polaron, exciton, and exciton-polaron revealed that the phenylimidazole type Ir emitter was relatively more resistant to the TPA degradation than the phenylpyridine type Ir emitter and extended the lifetime of blue phosphorescent organic light-emitting diodes. In addition, the lifetime and degradation of the short-living blue phosphorescent devices were improved by the host material suppressing the TPA under negative polaron using an electron scattering emitting layer structure.