KTP(001)晶体分光性能研究

根据同步辐射光源对软X射线分光晶体的性能要求,分析了软X射线能区常用分光晶体的性能优劣,指出对于晶格常数值大的分光晶体,KTP(KTiOPO₄)(011)是该能区比较理想的分光晶体. 同时提出了一种利用同步辐射光源测量晶体衍射效率的实验方法,指出光源的发散度与晶体的衍射效率密切相关. 测量了KTP(011)晶体的晶格常数,给出了KTP(011)晶体的实测衍射效率. 关键词： 同步辐射 KTP(011)晶体 衍射效率 光源发散度     

领结形中空表面等离子体波导的传输特性

设计了一种领结形中空表面等离子体波导.采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率、传播长度和模式面积随几何结构参数和工作波长的依赖关系进行了分析.结果表明,沿纵向的能流主要分布在两个上下突起所形成的中间区域.通过调整几何参数及工作波长,可以调节模式的有效折射率、传播长度和模式面积.在工作波长确定的条件下,有效折射率随突起半径的增大呈减小趋势,而传播长度和模式面积则随着突起半径的增大呈增大趋势,四个角上的圆弧半径对波导的传输特性有微调作用,左右扇形区域的半径对波导的传输特性有较明显 关键词： 集成光学 光波导 表面等离子体波导     

大气压等离子体针产生空气均匀放电特性研究

大气压空气放电由于脱离了真空装置,易于实现流水线生产,因而在工业上具有广泛的应用. 采用等离子体针装置在空气中产生了稳定的大气压均匀放电. 利用光谱法对等离子体的相关参数进行了空间分辨率测量,并通过光学方法对放电机理进行了研究. 结果表明,等离子体针产生的放电存在电晕放电和等离子体羽放电两种模式. 在稳定的等离子体羽放电模式中,发光分为强光区和弱光区. 弱光区放电的发展速度远大于强光区的发展速度,电子能量和电子密度均是弱光区比强光区大. 对均匀放电的气体温度和振动温度的研究表明,强光区放电遵循汤生击穿机理而弱光区为流光放电. 这些结果对大气压空气放电的工业应用具有重要意义. 关键词： 大气压均匀放电 等离子体针 发射光谱 放电机理     

变质量Chetaev型非完整系统Appell方程的Mei对称性和Mei守恒量

研究变质量Chetaev型非完整系统Appell方程的Mei对称性和Mei守恒量.建立变质量Chetaev型非完整系统的Appell方程和系统的运动微分方程; 给出函数沿系统运动轨道曲线对时间t全导数的表示式,并在群的无限小变换下,给出变质量Chetaev型非完整系统Appell方程Mei对称性的定义和判据;得到用Appell函数表示的Mei对称性的结构方程和Mei守恒量的表达式,并举例说明结果的应用. 关键词： 变质量 非完整系统 Appell方程 Mei守恒量     

相对运动动力学系统Appell方程Mei对称性导致的Mei守恒量

研究相对运动动力学系统Appell方程的Mei对称性及其直接导致的Mei守恒量.在群的无限小变换下,给出相对运动动力学系统Appell方程Mei对称性的定义和判据;得到相对运动动力学系统Appell方程Mei对称性的结构方程以及Mei对称性直接导致的Mei守恒量的表达式.举例说明结果的应用. 关键词： 相对运动动力学 Appell方程 Mei对称性 Mei守恒量     

含Stone-Wales缺陷zigzag型石墨烯纳米带的电学和光学性能研究

本文采用基于密度泛函理论的第一性原理对zigzag型石墨烯纳米带中含有不同Stone-Wales缺陷的电子结构特性和光学性能进行研究. 考虑了两种模型:不计电子自旋和考虑电子自旋的情况.研究发现:不计电子自旋情况下,含对称Stone-Wales缺陷的石墨烯纳米带在缺陷区域出现了凹凸不平的折皱构型,两种不同的Stone-Wales缺陷都引起了电荷的重新分布.考虑电子自旋时,Stone-Wales缺陷的引入对石墨烯纳米带自旋密度有显著影响,也引起了不同自旋的电子态密度的变化.进一步研究了纳米带的光学性能,发现 关键词： 石墨烯纳米带 Stone-Wales缺陷 电子结构 光学性能     

Thermoelectric properties and electronic structure of Al-doped ZnO

Impure ZnO materials are of great interest for high temperature thermoelectric application. In this work, we present the effects of Al-doping on the thermoelectric properties and electronic structures of a ZnO system. We find that, with increasing Al concentrations, the electrical conductivity increases and the thermal conductivity decreases significantly, whereas, the Seebeck coefficient decreases slightly. Nevertheless, the figure of merit (ZT) increases owing to high electrical conductivity and low thermal conductivity. On the other hand, the electronic band structures show that the position of the Fermi level is moved upwards and the bands split near the valence-band top and conduction-band bottom. This is due to the interaction between the Al3p and Zn4s orbitals, which drive the system towards semimetal. Besides, the Density Of States (DOS) analysis shows that the introduction of Al atom obviously reduces the slope d(DOS)/dE near the Fermi level. Based on the calculated band structures, we are able to explain qualitatively the measured transport properties of the Al-doped ZnO system.     

Ultrahigh sensitivity electric field detection with a liquid electro-optical film

In this Letter, an electro-optical probe configuration with polar molecule liquids as the sensing film is proposed to improve the voltage sensitivity. This method exhibited increases in intrinsic sensitivities better than 0.1 mV/√Hz, 2 orders of magnitude larger than the normal method using a GaAs probe in the same measurement system. Based on the mechanism of orientation polarization, the electro-optic coefficient was measured to be 250 pm/V by the Teng-Man method at a modulation field of 100 Hz. This technology will be promising in applications of low-frequency field detection.     

Bidirectional passively mode-locked soliton fiber laser with a four-port circulator

We present an all-fiber bidirectional passively mode-locked soliton laser with what we believe is a novel cavity configuration. Using a four-port circulator, we incorporate two different semiconductor saturable absorber mirrors (SESAMs) into the laser cavity, which enables bidirectional mode locking. The laser allows the generation of two independent countercirculating mode-locked pulse trains, each with an individual fundamental repetition rate that can be adjusted by varying the SESAM pigtail length. Two countercirculating pulse trains with repetition rates of 21.3 and 15.2 MHz are obtained simultaneously. By controlling the intracavity loss imposed on these two pulse trains, either one of the two pulse trains can be switched on or off. The bidirectional operation with other repetition rates is also demonstrated.     

Vectorial structure of far field of cylindrically polarized beams diffracted at a circular aperture

Based on the vector angular spectrum representation and the method of stationary phase, the analytical vectorial structure of the cylindrically polarized Laguerre-Gaussian beam diffracted at a circular aperture is derived in the far field, which provides an approach to further comprehend the vectorial properties of the apertured cylindrically polarized beams. The radially polarized, azimuthally polarized, and unapertured cases can be viewed as the special cases of our general result. The analyses show that the far-field energy flux distributions of the entire beam, the TE term, and the TM term depend on the beam order, the ratio of the waist width to the wavelength, the truncation parameter, and the angle between the electric field vector and the radial direction.