Optical characteristics of semiconductor saturable absorber mirrors investigated by the reflection Z-scan technique

Recently, the semiconductor saturable absorber mirror (SESAM) has become a key component of passive mode-locked solid-state lasers. Here we present a simple method based on the reflection Z-scan technique to measure the key optical parameters of SESAM such as saturation fluence and modulation depth. The experimental results demonstrate that our method is able to perform with a high accuracy of 10⁻⁴ and a dynamic range of over four orders of magnitude.     

Controlled quantum state sharing of arbitrary two-qubit states with five-qubit cluster states

In this paper, we propose a controlled quantum state sharing scheme to share an arbitrary two-qubit state using a five-qubit cluster state and the Bell state measurement. In this scheme, the five-qubit cluster state is shared by a sender (Alice), a controller (Charlie), and a receiver (Bob), and the sender only needs to perform the Bell-state measurements on her particles during the quantum state sharing process, the controller performs a single-qubit projective measurement on his particles, then the receiver can reconstruct the arbitrary two-qubit state by performing some appropriate unitary transformations on his particles after he has known the measured results of the sender and the controller.     

一种基于多特征融合的新型光谱相似性测度

光谱相似性测度是高光谱遥感影像定量化分析和精细地物直接识别的基础,光谱特征的选择和刻画方式是光谱相似性测度的关键.研究表明,利用光谱的单一特征无法全面反应地物光谱间的相似性,光谱识别时需要综合考虑光谱的多种特征.本文在几何距离、相关系数和相对熵的基础上提出了一种结合多种光谱特征的新型光谱相似性测度,即光谱泛相似测度(s...     

基于区间系统理论的分数阶混沌系统同步

通过设计一个非线性反馈控制器,实现了分数阶混沌系统的同步.与其他的分数阶混沌系统同步方法相比,提出的控制器设计方法保留了部分误差系统中的非线性项,而没有完全抵消同步误差系统的非线性项,有效改善了误差系统的控制性能.同时,应用区间分数阶线性时不变系统稳定性原理和线性矩阵不等式技术,得到了一个新的分数阶混沌系统同步的充分条件,进而获得的控制器保证了混沌系统同步.仿真结果验证了提出方法的有效性. 关键词： 区间分数阶时不变系统 分数阶混沌系统 混沌同步     

日盲紫外域拉曼激光雷达探测大气水汽技术研究

拉曼激光雷达通过探测与水汽浓度相关的大气水汽振动拉曼散射回波信号,可实现大气水汽混合比廓线的探测。然而由于振动拉曼信号非常微弱,在白天测量时振动拉曼散射光谱会淹没在太阳背景光中,多在夜间测量。为实现大气水汽的全天时测量,设计开发一套日盲紫外波段拉曼激光雷达系统。该系统选择Nd∶YAG脉冲激光器的四倍频输出-266.0 nm日盲紫外波段作为拉曼激光雷达系统的激励波长,采用镀高增益介质膜的牛顿式望远镜作为接收器,同时利用二向色镜和超窄带干涉滤光片设计高效率的高光谱分光系统,实现了大气氧气、氮气和水汽振动拉曼散射回波信号277.5,283.6和294.6 nm的精细提取。计算仿真结果表明,臭氧吸收对日盲紫外域拉曼激光雷达探测存在一定的影响,主要是探测距离的影响;氮气通道不受白天太阳背景光噪声的影响;水汽通道存在少量太阳背景光噪声,对系统探测距离略有影响。而系统信噪比计算结果表明,设计的日盲紫外域拉曼激光雷达系统可实现白天3.5 km大气水汽的探测。实际进行水汽探测时,可利用氮气和氧气通道反演出臭氧浓度廓线,修正臭氧对发射波长、各通道拉曼散射波长的吸收,进一步提升系统的探测能力和探测精度。     

三角形谱啁啾光纤光栅的制备及其在光纤无线单边带调制系统中的应用

本文涉及一种三角形谱啁啾光纤光栅的制备以及其在光纤无线(radio over fiber,RoF)单边带调制系统中的应用.基于相位掩模法和变速度折射率调制,实验制备了底部变化范围1.9 nm、透射深度0—15 dB的三角形谱啁啾光纤Bragg光栅,利用其透射谱具有较大负向斜边,研究了其在RoF系统中的应用.方案仅使用一个三角形谱光纤光栅,实现了以下两种功能: 1)双边带调制信号到单边带调制信号转换; 2)降低信号的载波边带比(carrier-to-sideband ratio,CSR),提高接收灵敏度.并 关键词： 光纤通信 微波光子 光纤布拉格光栅 单边带调制     

爆轰法合成碳包覆镍纳米颗粒的研究

 采用自制的负氧平衡复合炸药前驱体,在密闭容器中充氮气保护下爆轰合成了碳包覆镍纳米颗粒。利用X射线衍射、X射线荧光、透射电镜和拉曼光谱等技术,对爆炸产物的组成成分、结构形貌等进行了观测。结果表明,爆轰产物主要由具有面心立方结构的镍晶核和碳元素构成,此外还含有其它微量元素;合成的纳米颗粒呈球形或椭球形状,颗粒尺寸主要分布在10~25 nm范围,包覆的碳壳厚度约1~2 nm,核壳结构完备。结合观测结果,对爆轰法合成碳包覆纳米颗粒的形成机制进行了简单的讨论。     

Modified adaptive algebraic tomographic reconstruction of gas distribution from incomplete projection by a two-wavelength absorption scheme

A modified adaptive algebraic reconstruction technique (MAART) with an auto-adjustment relaxation parameter and smoothness regularization is developed to reveal the tomographic reconstruction of H 2 O distribution in combustion from incomplete projections. Determinations of relaxation parameter and regularization factor are discussed with regard to the consideration of improvement in reconstruction and reduction of computational burden. A two-wavelength scheme from tunable diode laser absorption measurement, 7444.36 and 7185.59 cm 1 , is used to simplify the nonlinear solution problem for obtaining the tomographic distributions of concentration and temperature simultaneously. Results of calculations demonstrate that MAART can perform the reconstruction results more efficiently with little complex modification and much lower iterations as compared with the traditional algebraic reconstruction technique (ART) or simultaneous iterative reconstruction technique (SIRT) methods. The stability of the algorithm is studied by reconstruction from projections with random noise at different levels to demonstrate the dependence of reconstruction results on precise line-of-sight measurements.     

大学物理实验数据分析与处理软件的研究与实现

本文针对开发计算机数据分析与处理软件来提高实验效率,保证实验教学的质量,介绍了软件的主要功能以及软件开发中遇到的一些问题和解决办法     

MOSFET调制器的实验研究

 介绍了MOSFET调制器的基本原理,并对其并联分流和感应叠加两种开关结构进行了实验研究。基于可编辑逻辑器件设计了其触发电路,驱动电路采用高速MOSFET对管组成的推挽输出形式,加快了MOSFET的开关速度。利用Pspice软件对开关上有无剩余电流电路(RCD)两种情况进行仿真,结果表明,加装RCD电路可以有效吸收MOSFET在关断瞬间产生的反峰电压。实验中,电流波形用Pearson线圈测量,用3个MOSFET并联作开关,当电容充电电压为450 V,负载为30 Ω时,脉冲电流13 A,前沿20 ns,平顶约80 ns;用3个单元调制器感应叠加,当电容充电电压为450 A,负载为30 Ω时,脉冲电流强度为40 A,前沿25 ns,平顶约70 ns。