宽调谐范围垂直腔面发射激光器特性分析及设计

运用光学传输矩阵和有限元方法对波长可调谐垂直腔面发射激光器(VCSELs)的波长调谐范围进行了研究.对中心波长为980nm的可调谐VCSELs的波长调谐特性和微电子机械系统(MEMS)悬臂梁结构进行了设计，并进行了实验研究.结果表明，MEMS可调谐VCSELs调谐特性同时受到光波谐振腔结构和悬臂梁最大位移的共同影响.在悬臂梁几何尺寸和激光器有源区结构一定的条件下，通过优化可调谐VCSELs的牺牲层厚度可实现大范围波长调谐.同时，对可调谐VCSELs整体结构进行了设计，计算结果显示波长调谐范围达到30nm以 关键词： 悬臂梁 可调谐垂直腔面发射激光器     

注入电流对垂直腔面发射激光器横模特性的影响

对980nm氧化限制型垂直腔面发射激光器横模进行测试和研究,理论上从时间、空间变量的速率方程出发,利用空间积分法分析了典型电注入参数对弱折射率导引垂直腔面发射激光器(VCSELs)横模行为的影响,通过实验测试,得到VCSELs的横模光场分布情况,并与理论分析进行对比,得出相应的实验结果,在氧化孔径不变的情况下,随着注入电流的增加,载流子分布从有源区中心向边缘移动,模式从低阶基模向高阶模转变,并发生了较强的模式竞争以及载流子空间烧孔效应,最终导致基模强度的降低.另一方面,通过比较不同注入孔径下高阶模的发生时 关键词： 横模 垂直腔面发射激光器 空间烧孔现象 模式竞争     

基于偏振旋转耦合1550nm垂直腔面发射激光器环形系统产生多路高质量混沌信号

提出了一种基于三个单向偏振旋转耦合1550 nm垂直腔面发射激光器(1550 nm-VCSELs)构成的环形系统获取多路高质量混沌信号的方案.利用自旋反转模型,数值研究了该环形系统中三个VCSELs的偏振分辨非线性动力学特性;利用自相关和互信息方法讨论了注入强度和频率失谐对三个VCSELs中各偏振分量输出时间序列的时延特征(TDS)的影响.研究结果表明:通过选择合适的注入强度和频率失谐,三个VCSELs均可同时输出X-偏振分量(X-PC)和Y-偏振分量(Y-PC)的平均功率可比拟的混沌信号,而且这些混沌信号的TDS通过进一步优化耦合参数可得到较好的抑制.在此基础上,进一步对三个VCSELs输出的六路混沌信号之间的相关性进行了分析,给出了除同一VCSEL输出的X-PC与Y-PC之间存在较强的相关性外其他信号之前关联性较弱的参数范围.     

基于椭偏光谱仪的石英晶体1310nm处双折射率的精密测量

为了对石英晶体在通讯波段1 310 nm处的双折射率进行精密测量,基于椭偏光谱仪对P和S两方向上偏振光相位差的精密测量原理,在透射模式下,通过对琼斯矩阵的分析,设计了一种精密测量晶体双折射率的方法,并在室温(22℃)下对通讯波段1 310 nm处石英晶体的双折射率进行了精密测量,测量结果和对误差的分析显示,此方法给出的...     

大功率垂直腔面发射激光器的相干性测量与分析

通过有机化学气象沉积(MOCVD)技术在n型GaAs衬底上生长制作了发射波长为850nm的VCSELs4×4列阵器件,介绍了VCSELs的制作工艺流程.对器件进行了相干性测量,计算了干涉条纹可见度,分析了影响干涉条纹可见度的因素.     

理论研究电流注入对垂直腔面发射激光器多横模行为的影响

从包含时空变量的速率方程出发,针对弱折射率导引垂直腔面发射激光器(VCSELs),利用空间积分法分析了典型电注入参数对VCSELs多横模行为的影响,在不降低模型准确性的前提下提高了仿真效率。仿真结果表明,注入盘孔径和注入环越小、注入强度越低以及电流扩散越弱时,VCSELs更易实现单横模工作;反之,VCSELs高阶横模开始出现并呈现较强的模式竞争,引发了载流子空间烧孔效应,并导致基模强度降低。进一步得出,在环形注入方式下,高阶模式更容易出现且彼此间的竞争较盘形注入时强。     

1550 nm垂直腔面发射激光器的特征参量随温度的变化

在采用自旋反转模型分析垂直腔面发射激光器（VCSELs）动力学行为的过程中,为了正确预测VCSELs的动力学行为,需要准确给出自旋反转模型中光场衰减速率k、总反转载流子衰减速率γ_N、线性二向色性系数γ_a、线性双折射系数γ_p、自旋反转速率γ_s和线宽增强因子α这6个特征参量.本文对1550 nm VCSELs在自由运行和平行光注入下的输出特性进行实验分析,获取了这6个特征参量的值,并着重研究了当激光器温度在10.00–30.00 ℃范围内变化时,这6个特征参量呈现的变化趋势.研究结果表明,随着温度的逐渐升高,γ_p整体呈现逐渐增加的趋势,γ_a,γ_s,γ_N和k呈现复杂的变化趋势,而α则呈现逐渐减小的趋势.     

激光在PERC晶硅电池中背面点接触电极制备中的应用

在经过Al2O3全钝化发射极钝化局部背接触(PERC)结构电池的背面实现良好的接触电极一直是制约着PERC高效电池向产业化推广的重要因素之一。本文采用532 nm激光烧蚀背面钝化介质层方法和传统的光刻工艺来实现背面电极的局部接触,并对两种方法进行详细的比较与分析。对激光烧蚀和激光烧结两种不同的局部接触电极制备方式进行了对比,发现激光烧蚀是更为适宜的工艺方式。相较于激光烧结,以激光烧蚀方式制备的电池的串联面接触电阻从10.7Ω.cm2降到1.24Ω.cm2,效率从4.2%提高到10.7%。     

关于制备1315nm 45°入射高反射镜的实验研究

从优化膜系、控制膜厚、改善膜面、均衡应力等四个方面开展了实验研究工作 ,为制备 1 31 5nm 4 5°高反射镜提供一些判断实验数据 ,并提出改进的方法 ,从而使制备的高反射膜取得满意的结果 :反射率大于 99.8%。     

表面等离子体调制的纳米孔径垂直腔面发射激光器

在普通850nm垂直腔面发射激光器基础上制备了表面等离子体调制的纳米孔径垂直腔面发射激光器.当小孔直径为200nm，周围光栅的周期为400nm时，在15mA驱动电流下最大输出光功率达到了0.3mW.介绍了该器件的制备工艺，并从实验和理论两方面分析了周期性光栅结构对光束的约束作用.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.