Vertical profile of aerosol extinction based on the measurement of O4 of multi-elevation angles with MAX-DOAS

A method for aerosol extinction profile retrieval using ground-based multi-axis differential optical absorption spectroscopy(MAX-DOAS)is studied,which is based on a look-up table algorithm.The algorithm uses parametric method to represent aerosol extinction profiles and simulate different atmospheric aerosol states through atmospheric radiation transfer model.Based on the method,aerosol extinction profile was obtained during six cloud-free days.The O4 differential air mass factor(dAMF)measured by MAX-DOAS is compared with the corresponding model results under different atmospheric conditions(R^2=0.78).The aerosol optical thickness,aerosol weight factor in boundary layer,and the height of the boundary layer are obtained after the process of minimization and look-up table method.The retrieved aerosol extinction in boundary layer is compared with PM2.5 data measured by ground point instrument.The diurnal variation trends of the two methods are in good agreement.The correlation coefficients of the two methods are 0.71 when the aerosol optical thickness is smaller than 0.5.The results show that the look-up table method can obtain the aerosol state of the troposphere and provide validation for other instrument data.

Determination of aerosol extinction coefficient and mass extinction efficiency by DOAS with a flashlight source

With the method of differential optical absorption spectroscopy （DOAS）, average concentrations of aerosol particles along light path were measured with a flashlight source in Chiba area during the period of one month. The optical thickness at 550 nm is compared with the concentration of ground-measured suspended particulate matter （SPM）. Good correlations are found between the DOAS and SPM data, leading to the determination of the aerosol mass extinction efficiency （MEE） to be possible in the lower troposphere. The average MEE value is about 7.6m^2.g^-1 , and the parameter exhibits a good correlation with the particle size as determined from the wavelength dependence of the DOAS signal intensity.

Wide-Band Polarization-Independent Semiconductor Optical Amplifier Gate with Tensile-Strained Quasi-Bulk InGaAs

A semiconductor optical amplifier gate based on tensile strained quasi bulk InGaAs is developed.At injection current of 80mA,a 3dB optical bandwidth of more than 85nm is achieved due to dominant band filling effect.Moreover,the most important is that very low polarization dependence of gain (<0 7dB),fiber to fiber lossless operation current (70～90mA) and a high extinction ratio (>50dB) are simultaneously obtained over this wide 3dB optical bandwidth (1520～1609nm) which nearly covers the spectral region of the whole C band (1525～1565nm) and the whole L band (1570～1610nm).The gating time is also improved by decreasing carrier lifetime.The wide band polarization insensitive SOA gate is promising for use in future dense wavelength division multiplexing (DWDM) communication systems.

Real Time Derivation of Atmospheric Aerosol Optical Properties by Concurrent Measurements of Optical and Sampling Instruments

The understanding of aerosol properties in troposphere, especially their behavior near the ground level, is indispensable for precise evaluation of their impact on the Earth’s radiation studies. Although a sunphotometer or a skyradiometer can provide the aerosol optical thickness (AOT), their application is limited to daytime under near cloud free conditions. In order to attain the multi-wavelength observation for both day- and night-time including cloudy conditions, here we propose a novel monitoring technique by means of simultaneous measurement using a nephelometer (450, 550, and 700 nm), an aethalometer (370, 470, 520, 590, 660, 880, and 950 nm), and a visibility meter (550 nm). On the basis of the multi-wavelength data of scattering and absorption coefficients from the nephelometer and aethalometer, respectively, first we calculate the real-time values of aerosol extinction coefficient in addition to the Angstrom exponent (AE). Then, correction of these values is carried out by comparing the resulting extinction coefficient with the corresponding value obtained from the optical data of visibility-meter. The major reason for this correction is the loss of relatively coarse particles due to the aerodynamic effect as well as evaporation of water content from particles during the sampling procedure. Then, with the ancillary data of vertical aerosol profile obtained with a lidar (532 nm), the temporal change of AOT is estimated. In this way, information from the sampling can be converted to the ambient properties in the atmospheric boundary layer. Furthermore, daytime data from a sunphotometer (368, 500, 675, and 778 nm) and a skyradiometer (340, 380, 400, 500, 675, 870, and 1020 nm) are used to validate the resulting AOT values. From the overall procedure, we can estimate the AE and AOT values from the sampling data, with uncertainties of approximately 5% for AE and 10% for AOT. Such a capability will be useful for studying aerosol properties throughout 24 hours regardless of the solar radiation and cloud coverage.

Optimization of Key Parameters in 622-Mb/s Amplitude Shift Keying Labeled 40-Gb/s Return to Zero Differential Phase Shift Keying Optical Switching Network

Optimized are the label extinction ratio and dispersion compensation of an optical label switching transmission system,which employs 40-Gb/s return to zero differential phase shift keying(RZ-DPSK)payload labeled with 622-Mb/s amplitude shift keying(ASK)control data.In our scheme,the receiver sensitivities of payload and label achieves-27.8dBm and-33.5dBm,respectively.After transmitted over 40km,60km and 80km single mode fiber(SMF)(with dispersion compensation)respectively,the payload can be recovered with no power penalty,while the label can be recovered with less than 2dB penalty.

Terahertz Time-Domain Spectroscopy method for optical parameter extraction of plastic materials

A method for extracting optical parameters of plastics materials based on terahertz time domain spectroscopy is presented. The transmission-type Terahertz Time-Domain Spectroscopy(THz TDS) system is adopted to detect the refractive index and extinction coefficient on different plastic materials. Then the corresponding spectral information is obtained by Fourier transform of the terahertz time domain waveform of the sampling points, including the corresponding amplitude and phase information of the waveform. The optical parameter extraction model is built. By using the simplex optimization method, the curves of the refractive index and extinction coefficient for the plastic material are obtained. The experimental samples are made of different plastic parallel plate materials. The experimental results show that the optimization of optical parameters can improve their extraction accuracy, and the error of refractive index is ±0.005. Extraction technology with the simplex optimization method of optical parameter based on THz TDS can help to extract the optical parameters of engineering plastics. It is of great significance for the research of terahertz nondestructive testing.

Inversion Methods of Optical Constants of Semitransparent Solid Materials from Transmittance Spectrograms

The direct calculation models of spectral transmittance of single and double slabs consisted of semitransparent solid materials were developed based on ray trace method, and a new inversion method of optical constants （k is extinction coefficient and n is refractive index ） of materials was proposed based on transmittance spectrograms of double slabs. Differences between the new method and two others currently used methods were studied, and application range of methods was also investigated. Optical constants of selenide glass attained in references were selected as true values, and spectral transmittances of glass simulated based on direct calculation model were regarded as experimental values. Optical constants of selenide glass were achieved by inverse models. Influences of measurement error on inverse results were also determined. The results showed that ： （ 1 ） based on transmittance spectrograms of double slabs in which thickness of single slab is the same, the new proposed method can attain optical constants of materials; （2） the effect of optical constants n and k on three inversion methods are urgent larger, but inversed calculation precision of optical constants are higher in most application ranges ; （ 3 ） the influence of measurement errors existed in experimental datum on the inverse precision of three methods are urgent distinctness.

Tunable Optical Bandgap of Gadolinium Substituted Nickel-Zinc Ferrite Nanoparticles-Effect of Calcination Temperature on Its Optical Parameters

The gadolinium substituted nickel-zinc ferrite nanoparticles of the composition, Ni0.5Zn0.5Gd0.05Fe1.95O4 were prepared using sol-gel method. In order to study the effect of calcination temperature on the optical parameters, the prepared powder was divided into five parts. The first part was taken as the as-prepared sample and the remaining four parts were calcinated at different temperatures, 600°C, 700°C, 800°C & 900°C. The X-ray diffraction patterns revealed the formation of cubic spinel structure with single phase and Fd3m space group. The crystallite size was increased from 11.75 nm to 18.13 nm as the calcination temperature increased from 600 to 900°C whereas as-prepared sample exhibited 17.61 nm. The dislocation density was decreased from 7.243 × 10-3 to 3.042 × 10-3 nm-2 as the calcination temperature increased from 600°C to 900°C. The micro strain was decreased from 10 × 10-4 to 6.452 × 10-4 as the calcination temperature increased from 600°C to 900°C. The characteristic absorbance peaks were obtained at 255.2 nm for the ferrite nanoparticles of as-prepared and calcinated at 600°C and 800°C whereas it was obtained as 252.8 nm for the sample calcinated at 700°C and there was no such characteristic peak in UV-visible range for the sample calcinated at 900°C;it is expected in the below 200 nm region. The optical energy gap was calculated using Kubelka-Munk equation based on Tauc’s plot and found in the range 4.100 eV to 5.389 eV. The lowest energy gap of 4.100 eV exhibited by the sample calcinated at 700°C and the highest energy gap of 5.389 eV by the sample calcinated at 900°C. It is concluded that the tunable band gaps can be obtained with varying calcination temperature.

Improved extinction ratio of Mach-Zehnder based optical modulators on CMOS platform

Silicon based optical modulators with improved extinction ratio （ER） of 25 dB were demon- strated on complementary metal oxide semiconductor （CMOS） platform. It was proposed that the effect of optical absorption due to free carriers accumulated in silicon should be considered in the analysis of device configuration. Experimental results presented in this study were identical with the proposed analyses. The modulators were operated with the data transmission rate of 3.2 Gbps.

Measurement of aerosol optical extinction using diode laser cavity ringdown spectroscopy

Accurate measurement of optical extinction of atmospheric aerosols is important for quantifying the direct climate effects of aerosols. A portable cavity ringdown spectrometer utilizing a modulated multimode blue diode laser (linewidth ～0.2 nm) is developed to measure the aerosol optical extinction. Laboratory generated ammonia sulfate particles (<1 μm in diameter) are characterized, with good agreements between the experimental measurements and Mie theory calculations. An optical extinction detection sensitivity of 0.24 Mm-1 (1σ) is achieved. Measurements of ambient aerosols are also carried out. This study demonstrates the feasibility of a compact, multimode diode laser cavity ringdown spectrometer for sensitive measurements of the optical extinction of atmospheric aerosols.

基于多项式求根的双厚度透射法确定液体光学常数

光谱反演法可实现液体光学常数(消光系数和折射率)的确定,其中双厚度透射法是有代表性的光谱反演法之一。由于液体自身无法形成确定的形状,需要盛放在透明容器(液体池)中,因而通过实验测量得到的光谱透射率包含了液体池光学常数的影响,这使得基于双厚度透射法所建立的光谱透射率方程极为复杂,难以求得解析解,通常采用反演法来计算液体的光学常数。现有的反演法存在如下问题:一是反演迭代耗费时间,二是反演迭代会引入误差,三是反演法得到的液体折射率存在二值问题。为解决上述问题,基于三层介质结构(液体池),考虑光在两种介质分界面上的多次反射,建立液体厚度满足整数比的光谱透射率方程组。通过代数运算获得与消光系数有关的多项式方程,求解并选择大于0小于1的实数根来计算消光系数;另求解关于液体池光学窗口反射率的一元二次方程,选择大于0小于1的根来计算液体和容器分界面的反射率,进而计算得到液体折射率的两个值。再用另一材料制作的液体池测量液体的光谱透射率,然后结合已经得到的消光系数作相关计算,会另外得到液体折射率的两个值,从四个值中选择相同者即为液体的折射率。作为应用示例,选用文献中水在0.5~1.0μm光谱范围的光学常数作为“理论值”、光学常数已知的石英玻璃和有机玻璃作为液体池材料。在不考虑仪器测量误差的情况下,将上述文献数据代入光谱透射率方程,计算得到的透射率作为“实验数据”。然后用多项式求根的方法确定水的光学常数,所得结果与“理论值”完全符合。模拟过程和计算结果表明:新方法是可用的,该方法解决了反演法的计算耗时、迭代误差以及折射率的二值问题,为液体光学常数的确定提供了一个新选择。

红外通信特性实验中用解析解计算材料的光学常数

在红外通信特性实验中测量材料的光学常数,可以通过测量反射率和透射率来获得,但现有的近似求解方法存在误差,并因此导致实验只能测量衰减很小或者很大的材料。针对此问题,通过求解关于待测量的方程组得到其解析解,由解析解可直接计算材料的消光系数、衰减系数和折射率,改进的计算方法具有更大的普适性。

天然焦内炭微球显微光学特征、成因及其意义

天然焦内炭微球是煤层遭受岩浆速热变质的产物,其显微光学特征成因解析有助于深入认识煤速热碳化和热变质。采集安徽淮北石台煤矿富含炭微球的天然焦样品,利用高分辨率反射偏光显微镜和扫描电镜等实验手段,表征了天然焦中炭微球的粒度、分布、显微光学和超微组构特征,以揭示其光学各向异性的成因和热演化意义。结果显示,远离岩体天然焦中炭微球以粗粒为主,粒径10~100μm,少数可达150μm以上;紧邻岩体天然焦炭微球以细粒为主,粒径1~10μm,在岩体内脉状焦内甚至低至1μm以下。分析显示,粗粒炭微球和炭半球分别发育“十字”消光和“波状”消光,是其内部放射状一轴晶光率体在切面内投影的光学表征;细粒炭微球发育“十字-双曲线”消光,是其内部放射排布的二轴晶光率体切片投影的旋转效应。由此可见,趋近岩体,伴随着镜质体反射率增加,煤焦光率体逐渐由规则球形(光性均质体),向二轴椭球体(一轴晶)和三轴椭球体(二轴晶)转变。在该过程中,“十字”消光和“波状”消光的粗粒炭微球是煤热脱挥发分的产物,而“十字-双曲线”消光的细粒炭微球是煤热缩聚而片层化的标志。天然焦中炭微球的显微光学特征是煤层趋热碳化的结果,本质上是其光率体受热变形的光学表征,可有效评价岩浆蚀变煤焦的热变质程度。

基于光学工程应用的全国陆地主要地区水平消光系数情况初步分析

从光学工程应用的角度对全国陆地主要地区水平消光系数情况进行了研究。首先从总体平均情况、冷暖半年、昼夜变化等三个方面对相关历史数据进行了分析。分析结果表明:总体上水平消光系数的呈现北低南高的分布;冷暖半年水平消光系数分布略有差别,暖半年水平消光系数低于冷半年的站点区域占较大面积;昼夜变化中白天水平消光系数要比夜间的消光系数偏小。在基于总体平均情况、冷暖半年、昼夜变化讨论基础上进而讨论了全国陆地主要地区水平消光系数的区域分级情况,发现适合光学工程应用的1级区主要分布在我国北方及西部地区。研究结果有助于了解全国适于开展光学工程应用的区域,并可为进一步研究水平消光系数对光学工程应用产生的定量影响提供参考。

随机数编码融合长脉冲级联调制提升Φ-OTDR定位性能

为解决随机数编码造成相位敏感光时域反射系统振动定位差的问题,设计了一种随机数编码融合长脉冲的级联调制方法,分别利用声光调制器和半导体光放大器实现随机数编码和长脉冲的融合调制,提升消光比。使用自相关的随机数编码生成脉冲序列,设计数字正交解调算法获得拍频信号幅值与相位信息。实验结果表明,在4km长度传感光纤上,脉冲宽度为40ns时,方案可将消光比提升13.7dB;当振动信号频率为200Hz时,振动信号定位均方根误差为2.1m,最大绝对误差为3.8m,提升了振动信号定位精度,为编码相位敏感光时域反射系统定位性能提升提供了新方法。

最小二乘法拟合大气激光雷达回波信号估算消光系数边界值

报道了一种使用最小二乘法拟合大气激光雷达回波信号,计算消光系数边界值的算法。对于无云层天气条件,利用最小二乘法对回波信号全程拟合获得大气消光系数边界值,在有云层天气下,先将激光雷达信号在大气中的传输光路分解为云层区和非云层区,忽略回波信号中的云层信息,并假设在非云层区大气近似均匀,利用最小二乘法拟合获得大气消光系数边界值。最后利用消光系数边界值求解激光雷达方程,反演获得大气消光系数。实际计算证明,用此算法可获得与实际更为接近的大气消光系数反演结果。

气溶胶粒子消光效率因子的特性研究及尺度谱的拟合

本文利用Mie散射理论,计算出单个球形粒子的消光效率因子Qext,分析它随半径r变化的特性。利用消光效率因子计算出Junge型气溶胶消光系数与波长的关系,并算出Deirmendjian型气溶胶的5种波长消光系数比值表(波长分别为355 nm、532 nm、683 nm、1064 nm、1560 nm),根据此表就可拟合出气溶胶的尺度谱。

成都地区中低云层的激光雷达探测

报道了应用Mie散射激光雷达探测云层的实验.利用改进的Klett反演算法对所测雷达回波信号反演获得大气消光系数分布,进一步求出云层高度、厚度及光学厚度.研究了云底高度和云层厚度在不同天气下的变化情况.获得了成都地区云层的一些重要信息,并对所得结果进行了分析讨论.

LiNbO_3外调制器的10 Gbit/s光纤传输系统

建立了一个10 Gbit/s光纤传输系统平台,实现了10 G光信号无中继、无误码传输,系统采用了NRZ码、高性能的GaInAsP多量子阱DFB激光器、LiNbO3电光调制器。进行了系统的传输实验,得到了系统的各项指标参数,分析了影响系统传输质量的因素,研究了传输系统中的一些关键问题。无中继距离为84 km,采用了CWDM技术对信号进行复用。在误码率为10-12时,接收机的最小接收光功率可达到-26.76 dBm。系统的功率代价为0.49 dB,没有出现误码率平台。实验还对发送光信号的消光比与接收机灵敏度之间的关系进行了研究,连续观察24 h无误码。

气溶胶后向散射消光对数比对消光系数反演的影响研究

使用Mie散射激光雷达在阴、雾和晴三种天气状况下采集了大气回波信号,从所测数据反演气溶胶消光系数的过程中发现,气溶胶后向散射消光对数比对反演结果存在较大影响。在阴天天气下,当后向散射消光对数比从0．7变化到1．0时,气溶胶消光系数反演结果相差近5倍;对晴天天气,反演结果相差近3倍; 而在有雾天气,其反演结果变化不大。通过参考大气能见度因子对消光系数进行修正,并从而获得对应的后向散射消光对数比,给出了一种根据天气状况确定气溶胶后向散射消光对数比的新方法。实际反演计算表明,用此方法可获得与实际更为接近的气溶胶消光系数。