Ratio of aerosol backscatter to extinction coefficients as determined from angular scattering measurements for use in atmospheric lidar applications

Wavelength dependence as well as relative humidity dependence of aerosol extinction to backscatter ratio was examined. The extinction to backscatter ratio is essential in solving lidar signal and was estimated from aerosol size distribution and refractive index (which were derived from angular light scattering measurements) using the Mie scattering theory. The extinction to backscatter ratios were calculated for wavelengths of 355 nm, 532 nm, 694 nm and 1064 nm, the major laser wavelengths used for lidars, where the refractive indices were assumed to be constant with wavelength. p ]When relating the aerosol extinction ₁ to the backscatter ₁ with a functional form of _{1 1} k ₁, the exponentk ₁ was evaluated by the least square method and tabulated for the four wavelengths. The extinction to backscatter ratio defined asS ₁= ₁/ ₁ was calculated and their dependence on the wavelength and relative humidity was examined. Their dependence on the relative humidity is small whileS ₁ in the average takes the value of 66 (±17), 60 (±13), 52 (±13) and 42 (±11) for the wavelengths 355 nm, 532 nm, 694 nm and 1064 nm, respectively     

Multiple regression equations for fractional concentrations of atmospheric aerosol and spectral extinction coefficients

We have studied the sensitivity of the coupling coefficients between the spectral extinction coefficients β(λ) and the fractional aerosol concentrations to microstructural variations in the aerosol. We have calculated and analyzed the spectral dependences of the correlation coefficients between the indicated characteristics. We have obtained the multiple regression equations for the fractional concentrations of background atmospheric aerosol and the spectral extinction coefficients at wavelengths of λ = 0.350 μm, 0.532 μm, and 1.060 μm with a large spread in the microphysical characteristics of the aerosol, allowing us to determine its fractional composition with accuracy that is satisfactory for many practical requirements, without using additional measurements of the microstructural parameters or taking into account their spatial variations. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 807–812, November–December, 2006.     

用于自由电子激光的光学速调管的设计与测试

详述了用于合肥自由电子激光用的光学速调管的物理设计与测试,以及光学速调管实际运行结果与升级计划。测试结果表明,考虑三维效应的OPERA3D场有限元计算法比解析设计更精确,多周期波荡器中任意周期磁场峰值受该周期外其它周期波荡器磁体的影响小于10%。     

用于自由电子激光的光学速调管的设计与测试

 详述了用于合肥自由电子激光用的光学速调管的物理设计与测试,以及光学速调管实际运行结果与升级计划。测试结果表明,考虑三维效应的OPERA3D场有限元计算法比解析设计更精确,多周期波荡器中任意周期磁场峰值受该周期外其它周期波荡器磁体的影响小于10%。     

载波调制激光雷达水下目标探测的仿真分析

激光雷达应用于水下目标探测,光信号受水体后向散射影响,导致目标对比度严重下降。一种以载波调制激光脉冲为探测信号的方法可实现对后向散射信号的抑制。利用基于蒙特卡罗的光子传输模型,模拟载波调制激光雷达水下目标探测的全过程。结果表明该方法对水下目标探测有明显改善,调制参数对探测性能有较大影响。     

Novel optical techniques for measurements of light extinction,scattering and absorption by single aerosol particles

Aerosol particles play important roles in a broad range of scientific disciplines, from atmospheric chemistry and physics, to the delivery of fuels for combustion and drugs to the lungs, and extending to industrial processes such as spray drying. Measurements of the light extinction, scattering and absorption by ensembles of aerosol particles can be used to non‐intrusively characterise aerosol particle samples. However, such measurements often lead to ambiguity in interpreting the properties and processes occurring on individual particles. In this review, recent developments in the use of laser based techniques to isolate and manipulate single particles and to characterise them will be highlighted. In particular, the use of cavity ring down spectroscopy, Bessel beams and optical tweezers for investigating light extinction, scattering and absorption, respectively, will be considered. The prospects for using optical techniques to interrogate the fundamental processes occurring in aerosol at the single particle level are discussed.     

Dynamic optical arbitrary waveform generation and detection in InP photonic integrated circuits for Tb/s optical communications

This article presents recent results in the development of optical arbitrary waveform generation (OAWG) technologies based on optical frequency combs and indium phosphide devices. A novel spectral-slice dynamic-OAWG approach and waveform shapers with customized spectral multiplexers and modulators, enable continuous generation of high fidelity optical waveforms accessing bandwidths in excess of 1 THz. We show results for two types integrated waveform shapers, a 100 GHz electrically controlled device with 10 channels spaced at 10 GHz and a 1 THz optically controlled device with 100 channels spaced at 10 GHz. Additionally, we include results from a 640 GHz waveform measurement device with 16 channels and 40 GHz spacing.     

An optical cuvette for orientation of gelatinous media and measurements of their spectral-polarization characteristics

The design characteristics of the optical cuvette suggested here provide the possibility of accomplishing the uniaxial orientation of gels with retention of the constancy of their volume, which makes it possible to carry out highly accurate polarization measurements with commercial spectropolarimeters in directions parallel and perpendicular to the axis of orientation. Using as examples polyacrylamide gels containing biologically important molecules and membranes, the possibility of measuring absorption spectra, the linear dichroism, and the dispersion of optical rotation is demonstrated. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 286–289, March–April, 1999.     

Multi-target retrieval (MTR): the simultaneous retrieval of pressure, temperature and volume mixing ratio profiles from limb-scanning atmospheric measurements

In this paper we describe a retrieval approach for the simultaneous determination of the altitude distributions of p, T and VMR of atmospheric constituents from limb-scanning measurements of the atmosphere. This analysis method, named multi-target retrieval (MTR), has been designed and implemented in a computer code aimed at the analysis of MIPAS-ENVISAT observations; however, the concepts implemented in MTR have a general validity and can be extended to the analysis of all type of limb-scanning observations. In order to assess performance and advantages of the proposed approach, MTR has been compared with the sequential analysis system implemented by ESA as the level-2 processor for MIPAS measurements. The comparison has been performed on a common set of target species and spectral intervals. The performed tests have shown that MTR produces results of better quality than a sequential retrieval. However, the simultaneous retrieval of p, T and water VMR has not lead to satisfactory results below the tropopause, because of the high correlation occurring between p and water VMR in the troposphere. We have shown that this problem can be fixed extending the MTR analysis to at least one further target whose spectral features decouple the retrieval of pressure and water VMR. Ozone was found to be a suitable target for this purpose. The advantages of the MTR analysis system in terms of systematic errors have also been discussed.     

Two-color cross-correlation of fs-laser pulses by two-photon induced photoconductivity for near and far field optical measurements

Two-color two-photon induced photoconductivity in a GaAsP diffusion type photodiode is demonstrated by measuring femtosecond cross-correlation functions for widely separated wavelength pairs of 775 and 1300 nm. Results are obtained for a range of tunable wavelengths and average powers of the incident lasers by measuring the two-photon induced photocurrent as a function of the optical delay between the pulses. The temporal autocorrelation of femtosecond laser pulses in the near-field of a small diameter aluminum coated optical fiber tip is also obtained with the same photodiode method for single colors.     

Molar coefficients of extinction for IR absorption bands of Ni(II) acetylacetonate, ketoiminate, and trifluoroacetylacetonate

We have studied IR absorption spectra (within the spectral range of 4000-200 cm⁻¹ of the intracomplex chelate compounds Ni(II) bis-acetylacetonate, Ni(II) bis-ketoiminate, and Ni(II) bis-trifluoroacetylacetonate and have given a full interpretation and comparison of the spectra of these compounds in dissolved and solid states. The reasons for the differences in the spectra are discussed. The molar coefficients of extinction for the absorption bands are calculated. Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 3, Akad. Lavrent’ev Ave., Novosibirsk, 630090, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 775–780, September–October, 1998.     

Growth and characterisation of new non linear optical material α-glycine sulpho-nitrate (GLSN) with stable dielectric and light dependent properties

Well defined transparent single crystals of α-glycine-sulpho-nitrate (GLSN) were obtained by slow evaporation of the solvent at room temperature. The new GLSN system crystallises in to orthorhombic symmetry with an indicative change in cell parameters depending upon the composition. CHNS, EDAX and proton NMR and carbon NMR analysis confirm the chemical units in the crystal. Comparative analysis of FTIR and laser Raman Spectra confirm the functional groups in the molecule. The TGA and DTA studies show presence of a transition anomaly at 413 K supported by resistivity and dielectric measurements. UV studies indicate wide transparency window with SWG conversion efficiency of 0.029 times of that of KDP material suggesting its use in optoelectronic devices. The crystal acts as a light sensor and exhibits light dependent nature indicative of conduction due of hydrogen ions with formation of space charge. The GSN crystal acts as a stable dielectric with a safe operating range of 300 volts/cm.     

Linear wavelength sweep of a semiconductor laser and its consequence for dispersion measurements and interference noise in optical fibers

The wavelength shift of a semiconductor laser during triangular pulse modulation has been investigated, using both a Michelson interferometer and direct spectral measurements. This property is used to establish a method for high-resolution dispersion measurements limited to 10 ps, and not affected by material dispersion or detector rise time. A theoretical investigation shows under what conditions the method is equivalent to the standard dispersion measurement setup. The technique is applied to measure polar mode dispersion in single-mode fibers. Examples of polarization noise caused by polarization anisotropy and the variation of source wavelength are presented.     

同步三通道激光告警光学系统有效孔径的确定及截获能量的估算

为了确定一种同步三通道激光告警光学系统的有效孔径并估算截获能量,建立了激光辐照远场传输模型,仿真研究了远场光斑半径、单通道入瞳半径和通道间相对能量差之间的数值关系.仿真结果表明:各通道之间最大相对能量差与远场光斑中心能量密度的大小无关,在激光远场光斑边沿处各通道之间的相对能量差最大;最大相对能量差限定时,远场光斑半径越大,允许的单通道入瞳半径也越大,但相应系统截获的脉冲能量或脉冲功率却相对减小;最大能量差限定为1%,远场光斑半径分别为2.5 m,4.0 m和7.5 m时,允许的最大单通道入瞳半径分别为3 mm, 5 mm和10 mm,相应系统截获的最大脉冲能量为1.14×10-5 J,7.54×10-6 J和2.68×10-6 J,最大脉冲功率为1.63 W, 1.08 W和0.38 W.     

Ultrasonic Nebulization/UV Photolysis Vapor Generation Sample Introduction System for the Determination of Conventional Hydride (As,Bi, Sb,Se, Sn) and Cold Vapor (Hg,Cd) Generation Elements in Reference Materials in the Presence of Acetic Acid by Microwave-Induced Plasma Spectrometry

ABSTRACT

A novel synergic effect of ultrasonic nebulization (USN) and ultraviolet (UV) radiation (photolysis) when used in combination has been exploited for efficient generation of conventional hydride elements (As, Bi, Sb, Se, Sn), Hg vapor, and volatile molecular Cd species. Several UV-based systems were studied, the most advantageous design being an ultrasonic nebulizer fitted with a 6 W mercury pen lamp supplying a microliter sample to a quartz oscillator, converting liquid into aerosol at the entrance of the UV spray chamber. Optimal conditions utilized a 40% v/v solution of acetic acid as the generation medium. The volatile species are detected by microwave-induced plasma optical emission spectrometry (MIP-OES). The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times the standard deviation of the blank (LOD, 3σ_blank criterion, peak height), were 11, 22, 16, 19, 20, 11, and 15 µg L^?1 for As, Bi, Sb, Se, Sn, Cd, and Hg, respectively. The method offers relatively good precision (RSD ranged from 3% to 5%) for liquid analysis and microsampling capability. The methodology was validated through determination of elements in two Certified Reference Materials (NRCC DOLT-2, NIST 1643e) and by the aqueous standard calibration technique.     

Calibration of mid-infrared transmission measurements for hydrocarbon detection and propane concentration measurements in harsh environments by using a fiber optical sensor

The local fuel concentration at the ignition position is a crucial parameter, especially for spark ignited engines. Hydrocarbon concentration can be determined by infrared transmission measurements because of the attenuation of infrared radiation in the 2940 cm⁻¹ frequency range due to the excitation of fundamental CH-stretch vibrations of the molecules. In-cylinder measurements can be done by modified spark plugs with integrated absorption paths. A tungsten halide lamp was used in the experiments as an infrared light source. There is a non-linear relation between measured transmissions and hydrocarbon densities. So far, infrared transmission measurements have to be calibrated on absolute density values by using various hydrocarbon test gases with different concentrations. Furthermore in-cylinder transmission measurements can be calibrated at homogeneous engine operation conditions. In this case, a well mixed air/fuel composition is expected at the end of the compression stroke. Both time-consuming calibration processes lead to a new calibration procedure for band integrated transmission measurements which is presented in this study. The non-linear correlations between band integrated transmissions and absorber densities were calculated by using the absorption cross section as a spectral characteristic of absorbing molecules and the filter transmission as the spectral influence of the experimental setup. The differences between measurement and calculation can be corrected by a single measurement using a test gas with known hydrocarbon concentration. The calibration procedure was verified on temperature and pressure influences by measurements using a heatable optical cell at pressures up to 1800 kPa and within a temperature range from 298 to 473 K. Finally, the calibration procedure was adapted from cell measurements to an infrared fiber optical sensor which was used for in-cylinder measurements. An adapter for the spark plug bore enables a parallel use of a flame-ionization-detector and the optical sensor. Simultaneous propane concentration measurements were made in a motored engine with both measurement systems.     

Investigation of intermodal interference of LP01 and LP11 modes in the liquid-core optical fiber for temperature measurements

The intermodal interference of the LP₀₁ and LP₁₁ modes and determination of the equalization wavelength in the liquid-core optical fiber is presented. Theoretically was described the weakly guiding optical fiber with the constant core radius, where equalization wavelength is a function of the refractive indices of core and cladding. The dependence of equalization wavelength on refractive indices is employed for measurement of temperature. Temperature sensitivity using intermodal interference of modes LP₀₁ and LP₁₁ was documented in the liquid-core optical fiber consisted of fused silica as cladding and medicinal oil as a core. In the investigated temperature range the intermodal interference allows the temperature measurement with resolution of about 0.02 °C.     

实现冷原子(冷分子)囚禁的可控制光学双阱的产生及其实验研究

简单介绍了实现冷原子或冷分子囚禁的可控制光学双阱的实验方案，报道了二元π相位板的制作方法及其产生可控制光学双阱的实验结果.分析了光学双阱参数(如空间位置、双阱中心间距、相对光强分布等)与π相位板相位偏差的关系.从理论和实验上研究了由于二元π相位板的刻蚀厚度误差引起的光学双阱光强变化及其双阱到单阱的演化规律，得到了实验与理论基本一致的结果. 关键词： 二元相位板 可控制光学双阱 冷原子囚禁 冷分子囚禁     

稀土元素(Ce,Pr)掺杂GaN的电子结构和光学性质的理论研究

采用基于密度泛函理论的第一性原理平面波赝势法计算了稀土元素Ce,Pr掺杂GaN的晶格参数、能带、电子态密度和光学性质,使用LSDA +U的方法处理具有强关联作用的稀土4f态,并分析比较计算结果.计算表明:掺入Ce和Pr后的体系相比未掺杂的GaN晶格常数增大,带隙变窄,并分别在禁带中和价带顶附近引入了局域的杂质能级,该能级主要由Ce和Pr的4f电子提供;掺杂后都发生了磁有序化并产生磁矩;最后定性分析了掺杂前后介电函数和光吸收系数的变化,掺Ce的体系在介电函数和吸收系数的低能区出现了峰值,该峰的出现和禁带中的杂质能级到导带底的跃迁有关,而掺Pr的体系由于带隙变窄使介电峰和吸收边发生红移.