激光对反舰导弹红外探测器干扰分析

针对激光对红外制导的反舰导弹干扰问题,建立了激光对反舰导弹红外探测器的干扰链路模型,推导了激光海上传输的大气透过率,计算了1．06μm激光在海上大气传输时仰角、能见度与大气透过率的关系,估算了对不同距离的反舰导弹红外探测器实现有效干扰所需发射的激光能量。     

高分辨傅里叶变换激光腔内吸收光谱方法：原理和应用

介绍了使用连续扫描方式工作的傅里叶变换光谱仪来探测激光腔内吸收光谱的原理,并探讨了傅里叶变换激光腔内吸收光谱方法测量光谱谱线和强度的工作方式.通过对大气中水汽在12450—12700cm^-1波段的高分辨吸收光谱的实际测量,检验了该方法的可靠性,并使用该方法测量了重水分子(D₂O和HDO)ν_OD=5伸缩泛频态光谱. 关键词： 激光光谱 高分辨振转光谱     

激光磁共振方法研究异戊二烯与NOx的化学反应

以激光磁共振为手段分别在紫外照射和火花放电条件下观测到异戊二烯与ＮＯ／ＮＯ２的反应，所获得的信息对了解大气化学反应及光化学烟雾有着重要的意义。     

湍流对地-空光通信系统性能的影响及自适应光学补偿

空间通信在地 空通信中具有广阔的应用前景。大气湍流引起的相位噪声会严重地影响系统的性能,而自适应光学补偿可使问题得到很好的解决。分析了湍流引起的相位噪声问题,并以Hufnagel湍流模型为例,借助结构函数的概念对这一噪声进行了计算。论证了自适应光学补偿方案。     

Laser induced medium perturbation in a pulsed CO2 laser

Laser induced medium perturbation (LIMP) has been identified by time-resolved interferometry observations of the lasing/non-lasing boundaries in a pulsed, kilojoule CO₂ electron beam laser, working at atmospheric pressure. This fundamental effect destroys the quality of the laser output beam and therefore has serious implications in laser design.     

Sealed Co Te laser

A UV pre-ionized TE ≈ 5.3 μm CO-He laser has been operated sealed-off for > 10⁵ pulses without any significant output power or energy deterioration. Laser action at up to atmospheric pressure has been obtained and an order of magnitude improvement in peak power output for electric discharge room temperature operation achieved.     

Joint influence of heterogeneous stochastic factors on bit-error rate of ground-to-ground free-space laser communication systems

Research methods for the formation of BER in the ground-to-ground Free-Space Laser Communication Systems (Free-Space Optics – FSO) with increased analytical effectiveness have been suggested. They correspond to physically rightful approximations with approbated quantity effectiveness. The methods have been used to study the influence of heterogeneous stochastic factors, such as: quantum noises, atmospheric transmittance fluctuations, mechanical vibrations of the transmitting laser antenna, atmospheric turbulence, on BER of FSO.

An algorithm for quantity estimation of the joint influence of all stochastic factors has been created. Numerical examples, illustrated by graphic material, have been shown.     

High power,subnanosecond pulse from a tea nitrogen laser with travelling wave excitation

A segmented flat-plate Blumlein circuit has been used to excite a travelling wave of inversion in pure nitrogen at atmospheric pressure in a 50 cm long discharge channel. UV laser emission in the forward direction was typically 200 times more intense than in the opposite direction. Laser pulse duration as determined by streak photography was 400 psec, whereas peak power was about 1 MW.     

On the Isstropic Nature of Laser Induced Infrared Fluorescence

Laser induced infrared fluorescence^1,2 is potentially a method for the remote detection of atmospheric pollutants.^3,4 An important parameter in the evaluation of this technique is the relationship between fluorescence intensity and the variation of the angle between the stimulating laser beam and the viewing direction of the detection system. It is important for monitoring procedures that the fluorescence be isotropic, otherwise the quantitative interpretation of the data becomes very complicated.     

氮氧化物与几种氯代烷烃化学反应的激光磁共振研究

以激光磁共振方法研究氮氧化物与二氯甲烷，三氯甲烷，四氯甲烷，１，２－二氯乙烷在紫外光照射和火花放电条件下的化学反应。实验结果表明氯代烷烃与ＮＯ／ＮＯ２在火花放电，紫外光照射条件下发生快速化学反应。所获得的信息对了解大气化学反应及光化学烟雾有着重要的意义。     

4.4 μm中红外激光外差光谱探测技术研究

在国内首次报道以窄线宽的4.4 μm外腔量子级联激光(QCL)作为本地振荡光源,黑体作为辐射光源的激光外差光谱实验装置的建立和测量工作。激光外差光谱是一种高灵敏度的光谱探测技术,并可以用于发展一种小型的光谱探测系统,进行地基或星载的地球大气或天文观测。介绍了激光外差的基本理论、装置的建立和实验测量工作。此激光外差光谱实验装置采用4.4 μm外腔量子级联激光,出光功率高达180 mW,在4.38～4.52 μm间连续可调,具有很宽的光谱调谐范围,能实现CO₂,CO和N₂O等大气重要分子的同时测量。通过开展不同压力下CO₂气体的激光外差光谱测量,对激光外差光谱实验装置的性能进行了评估。目前该激光外差系统的信噪比达到86,低于散粒噪声极限条件的理论计算值287,系统的光谱分辨率约为0.007 8 cm-1,能满足较窄线宽条件下的高分辨率激光外差光谱的测量。分析结果表明,中红外激光外差光谱系统具有很高的瞬态信噪比及光谱分辨率,在高精度测量大气温室气体的柱浓度和温室气体垂直廓线分布方面具有广阔的应用前景。     

基于激光外差技术的高分辨率整层大气透过率测量

激光外差技术是一种高灵敏度的光谱探测技术,利用该技术研制的装置易于集成化小型化,可以进行地基或星载的地球大气或天文观测。基于激光外差光谱测量技术,结合自研的太阳跟踪仪建立了一套高分辨率整层大气透过率测量系统,系统分辨率约为0.006 cm-1。该系统利用太阳光和红外激光在非线性探测器中进行光学混频,通过对获取的混频信号进行电子学滤波和平方率探测,获得了高光谱分辨率的外差信号。采用Langley-plot定标法对测量系统进行定标,获取了仪器标定常数和对应的大气总光学厚度,实现了中红外波段整层大气透过率的实时测量。同时,将实测整层大气透过率与MODTRAN5.0软件仿真计算的结果进行对比分析,两者的一致性较好。分析表明该测量系统具有很高的分辨率并且性能稳定可靠,在大气科学、天文观测和激光大气传输等研究领域具有广阔的应用前景。     

光腔衰荡光谱技术测定大气水汽稳定同位素校正方法研究

几乎所有小的气相分子（如H₂O,CO₂等）均具有独特的近红外吸收光谱,在负压条件下,每种微小的气相分子都拥有一对一的特征光谱线,基于这一原理人们开始使用激光光谱（IRIS）技术来准确分析气体样品中的同位素组成。该方法克服了传统同位素比质谱（isotope ratio mass spectrometry, IRMS）方法的局限性,已经成为公认的高精度、高灵敏度和高准确度的痕量气体检测方法。以大气水汽稳定同位素研究为例,大气水汽稳定同位素组成对水汽源区及其通道上的输送过程等水循环研究有着重要的指示意义。激光光谱技术使得大气水汽氢氧稳定同位素（δ18O和δD）野外原位连续高分辨率观测成为可能。但是,其观测精度和准确度受仪器运作特点、不同浓度大气水汽对特定光谱吸收性的敏感性差异等因素的影响,通常观测结果具有明显的非线性响应问题。因此,有必要对仪器观测过程中出现的各种偏差进行校正,但现阶段许多用户对新观测技术的国际校正方法尚不清楚。因此,基于波长扫描-光腔衰荡光谱（WS-CRDS）技术的大气水汽同位素观测系统（Picarro L2120-i）,通过可调谐二极管激光器（Tunable Diode Laser, TDL）发射可被待测气体分子所吸收的不同波长的激光,测量不同波长下的衰荡时间（即有样品吸收的衰荡时间）;TDL发射不能被待测气体吸收的不同波长的激光,测量每个波长下的衰荡时间（相当于无样品吸收的衰荡时间）。通过分析有无样品吸收的衰荡时间差,高精度计算待测气体的分子浓度,进而计算水汽稳定同位素组成。从记忆效应、漂移效应、浓度效应等方面,系统建立了一套准确可靠的大气水汽稳定同位素观测流程与校正方法,为正在使用或将要使用此类设备的研究人员提供参考,以获得高精度和高可靠性的大气水汽稳定同位素观测数据。     

Detection of sulphur dioxide in stack plume by laser Raman radar

Laser Raman radar offers a promising approach to the remote sensing of atmospheric pollutants in stack plume. An analysis revealed that the combination of the second harmonic of a Nd:YAG laser, a synchronous single photoelectron counting (SSPC) scheme, and narrow passband interference filter employed for light source, signal processor, and separation of Raman-scattered light respectively gave the most sensitive system for stack effluent monitoring. Using a laser Raman radar constructed on the basis of the analysis, the concentration of SO₂ in the plume emitted from a 150 m high stack of a power plant was measured at a distance of 228 m.This paper partly includes the material which was presented at the 1971 IEEE/OSA Conference on Laser Engineering and Applications (CLEA), Washington DC, USA, June 1971, as an invited paper (No. 19-2) in the session on Atmospheric Pollution.     

Surface impregnation by particle injection — laser impregnation

Wear resistance can be improved by laser impregnation — the surface layer of a base material is melted and hard wear resistant carbide particles are injected into the melted pool. Previously, experiments were mainly performed in a vacuum chamber at a laser power of 10 kW. In this paper, results are presented of experiments carried out with 1.5 and 2.5 kW lasers at ambient atmospheric pressure. Laser impregnated layers show increased wear resistance of the order of 20–40 times for impregnated compared to untreated aluminium, and 5–20 times for impregnated compared to hardened carbon steels.     

Tunable infrared laser instruments for airborne atmospheric studies

Tunable infrared laser-based instruments on airborne platforms have provided invaluable contributions to atmospheric studies over the past several decades. This paper presents an overview of some recent studies and developments using this approach that were presented at the 2007 Field Laser Applications in Industry and Research (FLAIR, http://www.inoa.it/flair/) conference in Florence, Italy. The present overview only covers select in situ absorption-based instruments that were presented in the airborne session at this conference. In no case are comprehensive details presented. These details can be found in the numerous references given. Additional approaches based upon cavity-enhanced and photoacoustic measurements, which are also making invaluable contributions in airborne atmospheric studies, are not discussed in this brief overview. PACS  07.88.+y; 07.57.Ty; 42.60.-v; 42.60.By; 42.62.Fi     

Detection of atomic oxygen in flames by absorption spectroscopy

The absolute concentration of atomic oxygen in an atmospheric pressure hydrogen/air flame has been measured using Intracavity Laser Spectroscopy (ICLS) based on a dye laser pumped by an argon-ion laser. Absorptions at the highly forbidden transitions at 630.030 nm and 636.380 nm were observed at an equivalent optical length of up to 10 km. The relatively low intensity of the dye laser avoids photochemical interferences that are inherent to some other methods for detecting atomic oxygen. The detection sensitivity is about 6 × 10¹⁴ atom/cm³ and can be improved with better flame and laser stabilization.     

Influence of the working conditions on nanofiber diameters obtained by laser spinning

Laser Spinning is a new technique that has been shown to quickly produce amorphous inorganic nanofibers from bulk material under atmospheric conditions. This technique employs a high power laser to melt a small volume of the precursor material while a supersonic gas jet provokes its rapid elongation and cooling, producing long micro- and nanofibers within a range of diameters. In this work, the quantity of the fibers produced and the distribution of their diameters are measured and statistically analyzed for different operating conditions. The advance speed of the laser beam over the precursor material is experimentally demonstrated to be the most influencing factor on the diameter of the fibers. Other variables of the process, such as assist gas pressure, were found to have less influence.     

Collisional Deactivation of Laser Induced Ethylene Fluorescence Lifetime of Vibrationally Excited Ethylene in Air at Atmospheric Pressure

Laser induced infrared fluorescence^1,2 is a potential method for the remote detection of atmospheric pollutants.^3,4 In evaluating this technique as a quantitative analytical tool, two important parameters are (a) the lifetimes of the excited species and (b) the quenching efficiencies of various molecules which would be expected to be in the atmosphere and which may collide with the excited species. Such quenching would lead to low fluorescence intensity and low analytical data. We have measured the quenching of the fluorescence of ethylene, which is a common hydrocarbon pollutant, by nitrogen, nitrogen saturated with water vapor, and air.     

Photonic sensing of the atmosphere by absorption spectroscopy

Chemically reactive atmospheric species play a crucial role in tropospheric processes which affect regional air quality and global climate change. Contrary to long-lived species such as greenhouse gases, interference-free accurate and precise concentration assessments of strongly reactive short-lived species represent a real challenge. In this paper, we report on the recent progress in spectroscopic instrumental developments for monitoring of OH, NO₃, HONO and NO₂ by using modern photonic sources (Quantum Cascade Laser, distributed feedback diode laser, light emitting diode) in conjunction with high-sensitivity spectroscopic measurement techniques such as multi-pass cell based long optical path length absorption spectroscopy, wavelength-modulation enhanced off-axis integrated cavity output spectroscopy, Faraday rotation spectroscopy, incoherent broadband cavity enhanced absorption spectroscopy. The main techniques available for routine atmospheric measurements of OH, NO₃ and HONO are overviewed, in comparison with the emerging modern photonic spectroscopy techniques.