Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Ultimate quantum limits for resolution of beam displacements

We compare two high sensitivity techniques which are used to measure very small displacements of physical objects by optical techniques: the interferometric devices, measuring longitudinal phase shifts, and the devices used to monitor transverse displacement of light beams. We detail the differences and the similarities for the quantum limits on the resolution of both systems. In both cases squeezed light can be used to resolve beyond the standard quantum limit and number correlated states allow us to reach the “Heisenberg” limit. Received 12 September 2002 Published online 21 January 2003     

内增强变象管相机中的干扰研究

本文讨论了带快门的内增强变象管相机的快门电路及其对扫描电路的干扰,干扰信号对相机性能指标的影响及解决方法。     

解联立方程组法校正火焰原子吸收光谱干扰

本文用解联立方程组法校正了火焰原子吸收分析中镓４０３．３０ｎｍ谱线对锰４０３．３１ｎｍ谱线的重叠干扰。实验结果表明：解联立方程组法是解决原子吸收光谱干扰的可能方法，该法在应用于合成的锰和镓测定中结果令人感到满意。     

Overlapping voltammetric peaks—an analytical procedure for simultaneous determination of trace metals. Application to food and environmental matrices

Voltammetric methods are very suitable, versatile and rapid techniques for simultaneous determination of metals in complex matrices. The present work, determination of Cu(II), Sn(II), Sb(III), Tl(I), and Pb(II) by square-wave anodic-stripping voltammetry and Cr(VI) by square-wave adsorptive-stripping voltammetry, is an interesting example of the possibility of simultaneous determination of each single element in food and environmental samples, even in the presence of reciprocal interference. Dibasic ammonium citrate, pH 6.3 or 8.2, was employed as supporting electrolyte. The voltammetric measurements were carried out using a stationary hanging mercury drop electrode as working electrode and a platinum electrode and an Ag|AgCl|KCl_sat electrode as auxiliary and reference electrodes, respectively. The analytical procedure was verified by analysis of standard reference materials—wholemeal BCR-CRM 189, wheat flour NIST-SRM 1567a, rice flour NIST-SRM 1568a, estuarine sediment BCR-CRM 277, river sediment BCR-CRM 320, and Montana soil with moderately elevated traces NIST-SRM 2711. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were generally below 6% whereas limits of detection for each element were below 0.069 g g^–1. In the presence of reciprocal interference the standard addition method considerably improved the resolution of the voltammetric technique, even for very high element concentration ratios. After being set up on the standard reference materials the analytical procedure was transferred and applied to commercial samples of meal and soil samples taken from sites devoted to agricultural practice. A critical comparison with graphite furnace atomic-absorption spectroscopy is also discussed. Work partially presented at Euroanalysis XIII, Salamanca, Spain, 5–10 September 2004     

利用光纤法布里-珀罗谐振器干涉透射波长同时测量混合溶液中多溶质浓度(英文)

为了同时探测混合溶液中多种溶质的浓度,提出一种用光纤法布里-珀罗谐振器作为传感器测量混合溶液中多溶质浓度的测量系统.从理论上分析了光纤法布里-珀罗谐振器干涉透射波长与混合溶液浓度之间的关系,采用光纤法布里-珀罗谐振器干涉透射波长实现了高准确度同时测量混合溶液中多溶质浓度的原理和可行性.构建了由InGaAs发光二极管光源、光纤耦合器、FFPR传感器、光电信号转换和放大器、光谱分析仪等组成的测量系统.对乙醇和甘油的9组标准混合溶液进行测量实验,并用测量结果标定了混合溶液中各溶质浓度与光纤法布里-珀罗谐振器传感器干涉透射波长之间的数学解析关系式.根据数学关系式用Action Script 2.0脚本语言编写程序,计算机实时监控了混合溶液中各溶质浓度的变化过程.     

Optical image encryption based on two beams’ interference

We proposed a method for optical image encryption on the basis of interference theory. An optical image can be produced by the interference of two beams passed two different masks. One of the masks can only modulate the phase of the beam and another can only modulate the amplitude of the beam. The encryption method is quite simple and does not need iterative algorithm. The results of simulation coincide with our method and demonstrate the feasibility of this method.     

Coherence and the statistics of the phase difference between partially polarized electromagnetic waves

Coherence between two vectorial harmonic light vibrations is analyzed in terms of the statistics of their phase difference. This provides a natural and simple extension of second-order coherence to cover more complicate situations. In particular this assigns large coherence to quantum light states providing the most accurate interferometric measurements allowed by the quantum theory, even if they are incoherent according to the standard second-order approach.     

An angle-resolved laser incident beam detector based on a pair ofFabry-Perot etalons

An angle-resolved laser detector based on a pair of a non-mechanical scanning Fabry-Perot cavities is described. The differential signal from the two cavities is approximately independent from the polarization of the incident laser beam and it is used to determine the angle of incidence of the beam on the Fabry-Perot cavities. The F-P etalon is made of interferometric filter combination. A laser incident angle sensor experimental platform is built up, and the experiment is carried out with a given laser range finder. When the incident angle is less than 5°, the transmission difference measured by the laser angle sensor is significantly lower than theoretical value, and deviation is more than 10%. When the incident angle is greater than 10°, the deviation is much lower than that of the situation of the incident angle is lower than 10°.     

Experimental determination of two-point Stokes parameters for a partially coherent broadband light beam

The generalized Stokes parameters, which are two-point extensions of conventional Stokes parameters, are determined for a pair of points in the cross-section of a partially coherent broadband light beam. For this purpose, using a two-mirror and two-beam-splitter assembly, unpolarized, linearly polarized and partially polarized electromagnetic beams are generated. This simple experimental method for determining generalized Stokes parameters establishes an analogy with the experimental scheme of determining conventional Stokes parameters, which in succession contributes to appreciable reduction in uncertainty in the measurements.