光电着舰引导设备激光单元作用距离研究

阐述了光电着舰引导激光测距/跟踪单元的工作原理,从人眼安全和大气窗口两方面讨论并确定了激光发射机波段。通过经验公式计算及MODTRAN实验对比研究了1.5x m全光纤激光的大气透过率。在精确计算大气双程透过率的基础上,分析了激光测距/跟踪单元不同气象条件下的作用距离。在晴与霾两种气象条件下,所设计的激光单元最大作用距离分别为10.8 km和8.5 km,满足光电着舰引导系统对跟踪距离大于6 km的指标要求。     

基于拉盖尔-高斯光束的单光子捕获概率研究

单光子源通常采用基于高斯光束的高度衰减激光脉冲,假设激光束具有初始高斯时域脉冲波形和TEM01模拉盖尔-高斯空域分布.基于折射率起伏的Rytov近似和修正von Karman谱模型,研究了大气湍流对星地量子通信单光子捕获概率的影响;建立了上行信道和下行信道的单光子捕获概率理论模型;针对低轨卫星-地面站间激光链路,对单光子捕获概率进行了分析.结果表明:上行信道的单光子捕获概率强烈依赖于地面折射率结构常数C2n(0),且随着C2n(0)的增加而减小;然而,下行信道的单光子捕获概率并不依赖于C2n(0),即大气湍流对其没有影响.     

Structural,optical,and electrical properties of Cu-doped ZrO_2 films prepared by magnetron co-sputtering

Copper(Cu)-doped ZrO_2(CZO) films with different Cu content(0 at.%～ 8.07 at.%) are successfully deposited on Si(100) substrates by direct current(DC) and radio frequency(RF) magnetron co-sputtering. The influences of Cu content on structural, morphological, optical and electrical properties of CZO films are discussed in detail. The CZO films exhibit ZrO_2 monocline(ˉ111) preferred orientation, which indicates that Cu atoms are doped in ZrO_2 host lattice. The crystallite size estimated form x-ray diffraction(XRD) increases by Cu doping, which accords with the result observed from the scanning electron microscope(SEM). The electrical resistivity decreases from 2.63 ?.cm to 1.48 ?·cm with Cu doping content increasing, which indicates that the conductivity of CZO film is improved. However, the visible light transmittances decrease slightly by Cu doping and the optical band gap values decrease from 4.64 eV to 4.48 eV for CZO films.     

Glow Discharge Characteristics of Hollow Needle-Plate Electrode in Atmospheric Pressure ArgonSCIEI北大核心CSCD

Atmosphere pressure uniform plasma has the broad application prospect in the industrial field. Using hollow needle cathode - plate anode device excited by direct-current voltage, a uniform and stable glow discharge is generated at atmospheric pressure in ambient air with argon used as working gas. The influence of the experimental parameters (including gas flow rate and the gas gap width) on discharge has been investigated by optical method. It can be found that a glow-discharge plasma column can bridge the two electrodes. The plasma column is uniform, and no filaments can be discerned. Near the plate electrode, the diameter of the plasma column is largest of all positions. The maximal diameter of the plasma column increases with increasing the discharge current or the gas flow rate. Through electrical method, the voltage-current characteristic has been investigated. It has been found that the discharge voltage decreases with increasing the current which is similar with the characteristic of glow discharge in low pressure. It increases with increasing the gas gap width or the gas flow rate. By analyzing the optical emission spectrum scanning from 330 to 450 nm emitted from the direct-current glow discharge, the molecular vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 have been investigated as functions of the gas flow rate and gas gap width. Results indicate that both the vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 decrease with increasing the gas flow rate or the gas gap width. In addition, the molecular vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 have been investigated in spatial resolution along the direction of gas flow(plasma column axial), and give a qualitative analysis as well. It is found that the vibrational temperature and the average electron energy increase with increasing the distance from the hollow needle cathode. These results are important to the industrial applications of glow discharge.     

液晶电光特性研究

随着近几年液晶显示技术在诸多领域的广泛应用和新技术的推出,人们一直致力于改善液晶器件显示性能的研究。在液晶显示器应用中,电光特性是一个很重要的参数,介绍了采用激光测量的方法获得液晶的电光特性、阈值电压及视角特性。分析了液晶分子在交流电场作用下重新取向后的扭曲特性,测试了不同电压下液晶分子的透光率和扭曲角度,结果表明:该方法是可行的,向列相液晶具有0.92 V较低阈值电压和较为陡峭的电光曲线,水平方向上在-60~+50有较好的视角特性,垂直方向上在-40~+20有较好的视角特性。该结论为偏光器件的设计与制作提供了依据。     

大气等离子体加工过程的原子发射光谱研究

大气等离子体加工反应过程中,等离子体发生装置的热稳定过程对去除率有直接影响,CF₄是化学反应中活性F*原子的提供者,O₂是重要的辅助气体。为了寻找这三者对大气等离子体加工反应过程的影响规律,采用大气等离子体加工系统进行加工、光谱仪监控等离子体反应过程的活性F*原子的光谱变化。实验结果表明,在大气压等离子体加工系统中: 热稳定后,活性F*原子强度基本不随时间变化;随着CF₄含量的增加,F*原子谱线轮廓发生了自吸收现象,这说明采用光谱法研究CF₄含量对活性F*原子含量的影响是不完全准确的;由于O₂易和CF₄解离的中间产物反应,抑制活性粒子重新组合,因此一定范围内随着O₂含量增加,活性F*原子增加。     

基于氧气A吸收带的baseline拟合距离反演算法

目标红外被动测距的实现同气体及其波段的选取密切相关。氧气A吸收带具有独特的谱线结构,对于火箭羽流或者高温辐射体的距离探测,氧气A吸收带是最佳的距离反演通道。利用该特点,详细研究了逐线积分算法(LBLRTM),并设计了氧气A带吸收系数及标准光谱计算软件;利用A吸收带吸收光谱带外数据,采用多项式拟合方法,实现基线(baseline)拟合,进而得到带平均透过率;在不同的距离条件下,将两种带平均透过率进行对比,误差在1.9%左右,拟合精度较高,该方法为后续距离的精确反演提供了理论依据。     

不同地区大气光学湍流内外尺度测量

 用光学湍流参数自动测量系统对内陆地区和沿海地区光学湍流内外尺度进行了大量的实验观测。分析了湍流尺度的日变化规律,给出了其频数分布。结果表明：两地内尺度的均值为十几mm,外尺度的均值约为2 m;内陆地区内尺度日变化趋势较为复杂,而外尺度的日变化趋势与湍流强度十分相似;沿海地区内外尺度与湍流强度均无明显关系。大气湍流尺度的大小和分布状态是随时间和空间变化的,因此,在估算实际大气湍流对光学系统的影响时,需要实测湍流尺度以便得到准确的结果。     

激光传输大气参量测量精度要求的数值分析

 就激光大气传输湍流热晕相互作用下大气参量测量误差对激光传输效果（平均功率密度）的影响进行了数值分析,并以典型的激光传输条件为例,分析了对激光大气传输影响最为敏感的3个大气参量——风速、吸收系数以及湍流结构常数的测量精度要求。综合不同传输距离下大气参量测量误差对传输效果的影响,大气风速的测量精度要求为±10%,吸收系数及湍流结构常数的测量精度要求分别为±5%和±15%。     

An airborne diode laser spectrometer for the simultaneous measurement of H2O and HNO3 content of stratospheric cirrus clouds

We describe a tunable diode laser spectrometer for the in situ simultaneous detection of the nitric acid and the water vapour by means of high resolution absorption spectroscopy on rovibronic lines, using a single laser emitting in the mid-infrared (5.8 μm) and a multipass cell. The instrument was designed to be installed on a high altitude aircraft, as a part of a composite payload for atmospheric aerosol studies. The instrument design criteria are discussed and the expected performances are compared with results of laboratory and field operation. Due to the high chemical activity of HNO₃, that makes difficult to use a reference cell, a fast sweep detection of direct absorption was used for the measurement. An absorption sensitivity of about 2×10⁻⁴ was achieved with an integration time of 2.5 s, corresponding to a concentration of about 4 ppb of HNO₃ in the cell and 0.1 ppb in the external aerosol. The data acquisition and processing techniques, based on the full molecular lineshape fitting are also shown and discussed, including some examples of the data acquired during the scientific flights.