轻微非共面腔的输出片应力作用研究

 建立了计算轻微非共面腔输出光椭圆度的数学模型,分析了R. H. Moore专利中的理论计算错误,计算分析了输出片的应力作用对输出光椭圆度的影响,发现：输出镜片的应力作用对环形激光器顺时针方向和逆时针方向输出光椭圆度的非对称有影响。通过实验验证了理论计算的正确性。得出R. H. Moore, S. W. Hammons等人在专利中提出的调腔方法存在错误,它不能有效地消除环形激光器中由腔体轻微异面所引起的磁效应。     

A diode laser spectrometer at 634nm and absolute frequency measurements using optical frequency comb

This paper reports that two identical external-cavity-diode-laser (ECDL) based spectrometers are constructed at 634 nm referencing on the hyperfine B-X transition R(80)8-4 of 127I2. The lasers are stabilized on the Doppler-free absorption signals using the third-harmonic detection technique. The instability of the stabilized laser is measured to be 2.8 × 10-12 (after 1000 s) by counting the beat note between the two lasers. The absolute optical frequency of the transition is, for the first time, determined to be 472851936189.5 kHz by using an optical frequency comb referenced on the microwave caesium atomic clock. The uncertainty of the measurement is less than 4.9 kHz.     

Nitrogen Dioxide Sensing Properties and Mechanism of Copper Phthalocyanine Film

Copper phthalocyanine film, a p-type organic semiconductor, is synthesized by vacuum sublimation and its surface morphology is characterized by SEM. A silicon-based copper phthalocyanine film gas sensor for NO2 detection is fabricated by MEMS technology. The results show that the resistance and sensitivity of copper phthalocyanine film decrease obviously as the NO2 concentration increases from Oppm to lOOppm. However, the sensitivity nearly keeps a constant of O. 158 between 30 ppm and 70 ppm. The best working temperature of the gas sensor is 90℃ for NO2 gas concentrations of lOppm, 20ppm and 30ppm, which is much lower than that of general metal oxide gas sensor.     

Stationary Fluid Dynamic Behaviour of V-Shaped Diffuser/Nozzle Elements for Valveless Micropump

A novel type of V-shaped （isosceles triangle cross-section） diffuser/nozzle element is proposed for use for valveless micropump. Stationary fluid dynamic behaviour of V-shaped diffuser/nozzle elements in a valveless micropump is investigated by experiment and simulation. Both the results agree well with each other when the Reynolds number is higher than 100 and the pressure loss coefficient ratio of micropump nearly always keeps a constant. For a single V-shaped diffuser, the general trends of variation of pressure loss coefficient with opening angle and Reynolds number are opposite in small and large angles. Compared with conical and flat-wall diffusers, V-shaped diffuser shows the smallest pressure loss when the Reynolds number is 200.     

Novel Image Optimization Method for Joint Photoacoustic Tomography

The distribution of speed of sound （SOS） in biomedical tissue and delay compensation （DC） have significant impact on the image quality of photoacoustic tomography （PAT）. When imaging human peripheral joints, using fixed SOS and DC can only ensure that the reconstructed images are focused in a limited depth range, whereas they are defoeused at other depths, which cause severe artifacts and blurring. In this work, a linear-DC based reconstruction approach is proposed to focus the whole PAT image region. It is proved by two in vivo experiments that, compared with traditional delay-and-sum back projection algorithms, the proposed method can effectively optimize the image quality of articular tissues in PAT.     

630nm-640nm波段半导体激光频率标准的研究进展

激光频率标准是将激光频率锁定于原子或分子的超精细能级间的稳定跃迁频率,从而获得高精度的激光频率输出[1-3].     

Mechanical Reinforcement and Piezoelectric Properties of PZT Ceramics Embedded with Nano-Crystalline

The double-scale lead zirconate titanate （PZT） piezoelectric ceramics were prepared by the solid state processing with PZT nano-crystalline and micro-powder. The microstructures, electrical and mechanical properties of the double-scale PZT are investigated. All the sintered ceramics exhibit a single perovskite structure and the grain size of the dou ble-scale PZT reduces due to the incorporation of PZT nano-crystalline. Compared to normal PZT, the mechanical properties increase significantly and the piezoelectric properties decrease slightly. Mechanisms responsible for the reinforcement of the double-scale PZT are discussed.     

Mechanism of Enhanced Dielectric Properties of SiC/Ni Nanocomposites

Dielectric properties of SiC/Ni nanocomposites prepared by a simple and facile electroless plating approach at X band are investigated. Compared to the original SiC nanopartieles （SiCp）, the real part of the permittivity, ε＇, and the dielectric loss tangent tang δe of SiC/Ni nanocomposites are clearly enhanced by about 31% and 33%, respectively. The effective equations for complex permittivity of SiC/Ni nanoeomposites are proposed. We also calculate ε＇ and tan δe of SiC/Ni nanoeomposites and the calculated results are well consistent with the measured data.     

四频差动激光陀螺的磁敏感性与最佳工作点

为了减小四频差动激光陀螺(DILAG)的磁敏感性,研究了工作点对磁敏感性的影响.根据理论分析,磁敏感性主要来自于左、右旋陀螺相对比例因子修正的不对称,它与工作点有关,在最佳工作点下为零.通过在DILAG增益管上缠绕线圈产生轴向磁场,调节附着于腔平移镜上的压电换能器的驱动电压改变工作点,得到磁灵敏度随工作点的变化规律.结果表明,DILAG在最佳工作点下对外界磁场不敏感,且在每个工作区存在唯一的最佳工作点.DILAG工作在最佳工作点可以使外界干扰在差动中消除,因而有利于提高其性能.为了保证DILAG工作在最佳工作点,必须改变传统的光强差稳频方式.     

Structural and electrical properties of Nd ion modified lead zirconate titanate nanopowders and ceramics

A modified sol-gel method is used for synthesizing Nd ion doped lead zirconate titanate nanopowders Pb1-3x/2NdxZr0.52Ti0.48O3 (PNZT) in an ethylene glycol system with zirconium nitrate as zirconium source. The results show that it is critical to add lead acetate after the reaction of zirconium nitrate with tetrabutyl titanate in the ethylene glycol system for preparing PNZT with an exact fraction of titanium content. It has been observed that the dopant of excess Nd ions can effectively improve the sintered densification and activity of the PNZT ceramics.Piezoelectric, dielectric and ferroelectric properties of the PNZT ceramics are remarkably enhanced as compared with those of monolithic lead zirconate titanate (PZT). Especially, the supreme values of piezoelectric constant (d33) and dielectric constant (ε) for the PNZT are both about two times that of the monolithic PZT and moreover, the remnant polarization (Pr) also increases by 30%. According to the analysis of the structures and properties, we attribute the improvement in electrical properties to the lead vacancies caused by the doping of Nd ions.