2007, 5(1) Column
Chinese Optics Letters 第5卷 第1期
Measurement of scintillation and link margin for laser beam propagation on 3.5-km urbanised pathDownload:2808次
An experiment of laser propagation was carried out at the urban terrain range of 3.5 km during the period of March to May of 2006. The received intensity scintillations and atmosphere turbulence strength in complex urban atmosphere circumstance were simultaneously measured concentratively. The results show the statistical characteristics of irradiance scintillation and atmosphere turbulence strength and link fade margin for urban free-space optical links.
大气与海洋光学 空间光通信 大气闪烁 链路冗余 060.4510 Optical communications 010.1300 Atmospheric propagation 010.7060 Turbulence Dispersion and dispersion slope compensation of 10-Gb/s pulses using microstructure fibers (MFs) is demonstrated experimentally. A 26-m MF is used to compensate the dispersion of 2-km standard singe mode fiber in a 20-nm range in C band. The experimental results show that a significant improvement can be achieved in the quality of the observed pulses with the dispersion compensation. Moreover, the further research shows that the MF can compensate the anomalous dispersion of a single mode fiber within +-0.27 ps/(nm.km) over a 50-nm wavelength range from 1520 to 1570 nm.
光纤通信 光子晶体光纤 微结构光纤 色散补偿 色散斜率 060.2330 Fiber optics communications 060.2310 Fiber optics A novel scheme of label abstraction and erasion based on Fabry-Perot semiconductor optical amplifierDownload:899次
A novel label abstraction and erasion scheme based on a Fabry-Perot semiconductor optical amplifier (FP-SOA) is proposed for all-optical separation of the bit-serial label from payload and its performance is investigated by simulation. Important features of this scheme are that it does not make use of any high-speed electronics and only one device is needed. Using this scheme, label abstraction and erasion can be realized with the extinction ratio of 9.72 and 7.05 dB, respectively.
光纤通信 标签提取 标签擦除 光分组交换网络 光标签处理 比特序列型 法布里-珀罗半导体光放大器FP-SOA 060.4510 Optical communications 060.1810 Buffers, couplers, routers,switches, and multiplexers 070.4340 Nonlinear optical signal processing The limitation of paraxial condition of paraboloid refracting system in performing fractional Fourier transform acts like an aperture, which makes the system different from ideal systems. With aperture expanded as the sum of finite complex Gaussian terms, a more practical approximate analytical solution of fractional Fourier transform of Gaussian beam in an apertured paraboloid refracting system is obtained and also numerical investigation is presented. Complicated and practical fractional Fourier transform systems can be constructed by cascading several apertured paraboloid refracting systems which are the simplest and the most basic units for performing more precise transform.
傅里叶光学 抛物面折射系统 分数傅里叶变换 孔径 近轴条件 070.2590 ABCD transforms 050.1220 Apertures 120.4820 Optical systems 140.3300 Laser beam shaping Rotation, scaling, and translation invariant local watermarking technique with Krawtchouk momentsDownload:663次
A rotation, scaling, and translation invariant local watermarking is proposed with one or two Krawtchouk moment(s) of the original to estimate the geometric distortion parameters including rotation angle, scaling factor, and translation parameter. Krawtchouk moments can be used as private key of watermark extractor. Watermark is inserted into perceptually significant Krawtchouk moments of original, and watermark based on Krawtchouk moments is local. Independent component analysis (ICA) is utilized to extract watermark blindly. Experimental results show that this method has a good robustness against distortions preformed by watermark benchmark -- Stirmark.
图像处理 几何攻击 Krawtchouk矩 局部水印技术 Stirmark 100.0100 Image processing 100.2000 Digital image processing A hybrid algorithm based on seeded region growing and k-means clustering was proposed to improve image object segmentation result. A user friendly segmentation tool was provided for the definition of objects, then k-means algorithm was utilized to cluster the selected points into k seeds-clusters, finally the seeded region growing algorithm was used for object segmentation. Experimental results show that the proposed method is suitable for segmentation of multi-colored object, while conventional seeded region growing methods can only segment uniform-colored object.
图像分割 图像处理 图像分析 种子生长 100.2960 Image analysis 100.5010 Pattern recognition 100.3010 Image reconstruction techniques A novel color correction algorithm for noisy multi-view images is presented. The key idea is to use the improved Karhunen-Loeve (K-L) transform to obtain correction matrix that can eliminate noise effect to the fullest extent. Noise variance estimation is first performed in the algorithm. In the end, wavelet transform is applied to denoise the corrected image. Experimental results show that, compared with traditional correction method, a well-performed correction result is achieved using the proposed method, and the visual effect of the denoised corrected image is almost consistent with ideal corrected image.
图像处理 颜色校正 噪声多视点图像 K-L变换(Karhunen-Loeve变换) 噪声方差 110.0110 Imaging systems 100.6890 Three-dimensional image processing 330.1690 Color Calculation method for particle mean diameter and particle size distribution function under dependent model algorithmDownload:4599次
In total light scattering particle sizing technique, the relationship among Sauter mean diameter D32, mean extinction efficiency Q, and particle size distribution function is studied in order to inverse the mean diameter and particle size distribution simply. We propose a method which utilizes the mean extinction efficiency ratio at only two selected wavelengths to solve D32 and then to inverse the particle size distribution associated with Q and D32. Numerical simulation results show that the particle size distribution is inversed accurately with this method, and the number of wavelengths used is reduced to the greatest extent in the measurement range. The calculation method has the advantages of simplicity and rapidness.
光全散射法 粒径分布测量 双波长法 290.2200 Extinction 120.5820 Scattering measurements 300.6360 Spectroscopy, laser Phase locking of two beams emitting from a side pumped Nd:YAG slab with self-imaging resonatorDownload:595次
Intracavity phase locking of two beams emitting from a block of Nd:YAG medium side-pumped by laser diode array (LDA) was investigated experimentally. The interference fringes of the two beams occured at the output mirror. The coherent output power of 1.13 W was obtained with combination efficiency of 64.9% and coherence degree of about 60%. Only a metallic wire as a filter located at a suitable position close to the output mirror can efficiently lock the entire structure with less than 8% power loss.
激光光学 激光技术 相干合束 位相锁定 140.0140 Lasers and laser optics 030.1640 Coherence 140.3290 Laser arrays 140.3480 Lasers, diode-pumped The frequent defects of the metal parts, such as non-fully melting, thermal strain, and balling, which are produced by selective laser melting (SLM) that is a novel method of one-step manufacturing, are analyzed theoretically and experimentally. The processing parameters significantly affect the quality of the final parts, and simultaneously, the appropriate laser mode and the special scanning strategy assure a satisfying quality of the final parts. The SLM experiment is carried out using Cu-based powder. The metal part is divided into several scanned regions, each of which is scanned twice at the cross direction with different scanning speeds. The microstructure is analyzed on microscope. The results show that the part is metallurgically bonded entity with a relative density of 95%, and the microstructure is composed of equiaxial crystal and dendritic crystal whose distributions are mainly decided by the scanning strategy.
激光加工 选区激光熔化 快速成型 金属零件 140.3390 Laser materials processing 310.3840 Materials and process characterization 310.1860 Deposition and fabrication Study on the approximative formula for the far-field of a Gaussian beam under circular aperture diffraction and its divergenceDownload:1409次
The approximative formula for the far-field diffraction of a Gaussian beam through a circular aperture is obtained by using the superposition of Gaussian beams instead of the aperture function, and the explicit expression for calculating the beam divergence is also gained. Using the formula, the influences of the aberrations on the far-field wavefront and the beam's divergence are researched, and the results show that the large aberrations badly affect the far-field wavefront and the divergence. It is suggested that the aberrations and the diffractions should be avoided when designing the transmitter.
衍射 波前 发散度 050.0050 Diffraction and gratings 050.1970 Diffractive optics The effects of B/(B+Al) ratio on glass formation regions and properties of phosphate edge-cladding glassesDownload:681次
The glass-forming region of P2O5-Al2O3-B2O3-ZnO-Na2O-CuCl system with different Al2O3 and B2O3 contents was studied. The dependence of glasses properties on B/(B+Al) ratio was investigated. The absorption coefficient of copper ion in a specific glass was measured. These results are very helpful to the designing of a cladding glass for large size neodymium phosphate glass.
玻璃 光学材料 光学性质 热膨胀 160.4760 Optical properties 160.4670 Optical materials 160.2750 Glass and other amorphous materials 140.4480 Optical amplifiers 140.3380 Laser materials Using power spectral density (PSD) function to specify large aperture optical components' quality of laser system is universal. But it cannot provide effective guidance to eliminate certain frequency segment error. In order to solve this problem, two-dimensional discrete wavelet transform (2D-DWT) is used to separate frequency segment error and detect the corresponding region of certain frequency segment error, which is used as feedback to a machining process. The experimental results show that the corresponding region of certain frequency segment can be found and machining can be guided effectively by using wavelet.
光学设计与制造 光学评价 二维离散小波变换 220.4880 Optomechanics 100.7410 Wavelets 120.0120 Instrumentation, measurement, and metrology Faraday rotation in a resonant five-level system via electromagnetically induced transparencyDownload:516次
We study the Faraday rotation of polarization of a probe field in a cold, coherently driven five-level system with an M-type configuration. By means of a method of multiple scales we derive two coupled nonlinear envelope equations, which govern the evolution of two circularly polarized components of the probe field. It is shown that due to the quantum interference effect induced by two control fields, one can obtain a large rotation angle with a very low absorption of the probe field. In addition, an efficient control over the polarization state of the probe field in the system can also be easily realized.
量子光学 电磁感应透明 法拉第旋转 270.1670 Coherent optical effects 270.4180 Multiphoton processes 260.1440 Birefringence 260.5430 Polarization A novel approach for detecting laser radar target based on multi-fraction dimension (MFD) of laser clutters has been proposed. The fractal dimension (FD) of laser clutter and the echoes from the plan are estimated using box-counting dimension algorithm. The intrinsic difference in the spectrum of FD Dq between them is extracted and used to detect targets. Experimental results show that the method based on MFD is more reliable than that on FD and can improve the accuracy of detection.
遥感 多重分形维 计盒维 目标检测 激光雷达 040.0040 Detectors 120.0120 Instrumentation, measurement, and metrology 140.0140 Lasers and laser optics A high sensitivity spectrometer with tunable diode laser for ambient methane monitoringDownload:805次
Tunable diode laser absorption spectroscopy (TDLAS) has been widely employed in atmospheric trace gases detection. In the measurement of these trace gases, harmonic detection combined with a multi-pass white cell could remarkably enhance the detection sensitivity. In this paper, a portable TDLAS system built specifically for long time monitoring methane in the atmosphere is introduced. The detection limit is below 100 ppb that is enough for the monitoring of ambient methane, and the long time monitoring results obtained in Beijing are given, which is well coincident with that of the Fourier transform infrared (FTIR) spectroscopy.
测量 可调谐半导体激光吸收光谱 甲烷 多次反射池 300.6340 Spectroscopy, infrared 280.0280 Remote sensing and sensors 300.6260 Spectroscopy, diode lasers 300.6380 Spectroscopy, modulation Laser-induced breakdown spectroscopy based detection of lunar soil simulants for moon explorationDownload:744次
A scientific goal of the moon exploration project is to perform elemental analysis on the moon surface. The assuming of using laser-induced breakdown spectroscopy (LIBS) for this goal has been put forward. The laser plasma used by LIBS is sensitive to the surrounding atmosphere and the moon has very low ambient gas pressure on the surface, so the study of the LIBS capabilities at the low pressure was carried out.
激光诱导离解光谱技术 模拟月壤 月球探测 元素分析 140.3440 Laser-induced breakdown 300.2530 Fluorescence, laser-induced 300.6210 Spectroscopy, atomic 240.6670 Surface photochemistry Design and preparation of frequency doubling antireflection coating with different thicknesses of interlayer were investigated for LiB3O5 (LBO) substrate. The design was based on the vector method. The thickness of the inserted SiO2 interlayer could be changed in a wide range for the four-layer design with two zeros at 1064 and 532 nm. The coatings without any interlayer and with 0.1 quarter-wave (QW), 0.3 QW, 0.5 QW SiO2 interlayer were deposited respectively on LBO by using electron beam evaporation technique. All the prepared coatings with SiO2 interlayer indicated satisfying optical behavior. This expanded our option for the thickness of an interlayer when coating on LBO substrate. The prepared films with SiO2 interlayer showed better adhesion than that without any interlayer. The thickness of the interlayer affected the adhesion, the adhesion for the coating with 0.5 QW SiO2 interlayer was not as good as the other two.
光学设计和制备 光学薄膜 非线性光学材料 附着强度 220.0220 Optical design and fabrication 310.6860 Thin films, optical properties 160.4330 Nonlinear optical materials Generation of millimeter-wave sub-carrier optical pulse by using a Fabry-Perot interferometerDownload:509次
A novel scheme is proposed to transform a Gaussian optical pulse to a millimeter-wave (mm-wave) frequency modulation pulse by using a Fabry-Perot interferometer (FPI) for radio-over-fiber (ROF) system. It is shown that modulation frequency of mm-wave is determined by the optical path of the Fabry-Perot (F-P) cavity, and amplitude decay time and energy transfer efficiency are related to the reflectivity of the F-P cavity mirror. The effect of pulse train extension on inter-symbol interference is also discussed.
光纤光学 毫米波脉冲 法布里-珀罗干涉仪 光纤无线电系统(ROF) 微波光子学 060.0060 Fiber optics and optical communications 060.2340 Fiber optics components 350.4010 Microwaves 动态信息
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