基于卓越工程师培养目标下的大学物理实验创新培养模式

针对卓越工程师的基本训练要求及社会发展的需要,以“卓越工程师”培养目标为导向,以辅助教学系统、实验数据处理系统和学生创新实践平台三大模块为依托,根据学生学习的不同阶段和知识积累过程,建立全方位、模块化、逐层深入的实验教学培养模式,把大学物理实验室建设成培养学生创新能力的重要基地.     

大倍率红外连续变焦系统双电机控制技术研究

采用双电机联动控制变倍组与补偿组的变焦方案替代传统的曲线套筒,实现了采用全透射式结构型式,相对口径为1/4,焦距变化范围为342.76 mm~13.15 mm连续变焦光学镜头的机械补偿式变焦。将变倍组设计成步进模式,作匀速运动,补偿组设计成位置跟踪模式,按凸轮曲线作变速运动,采用双电机全数字伺服控制凸轮（CAM）算法,将光学设计计算的变倍镜和补偿镜位置对应关系转变为对应的脉冲数输入到CAM表中,从而确定2个不同运动速度轴之间的位置对应关系。试验结果表明:双电机控制的变倍组和补偿组位置分辨率达到0.18 m,光轴一致性水平方向达到1.9,垂直方向达到1.3。     

二极管泵浦激光器中泵浦光分布对激光器模式影响程度的计算方法

在激光器中,通常泵浦光呈不均匀分布,由此引起介质的增益也相应地出现不均匀分布,导致振荡光通过增益区时其分布发生变化。提出一种计算不均匀的泵浦光分布对于激光器内振荡光模式的影响程度,可以近似获得振荡光对原来场分布偏离的百分比的方法。在此基础上,对准连续运转的三向侧面泵浦激光器进行研究,分析不均匀泵浦光分布对振荡光场影响的规律。结果表明:当泵浦功率增加或谐振腔内损耗增加时,振荡光通过增益区时对原来分布的偏离程度也同时增加,呈单调变化关系;泵浦光不均匀分布对振荡光场的影响,与其沿振荡光轴向上的分布无关,仅仅取决于其在与振荡光垂直方向上的不均匀分布程度。通过计算还获得了此类效应的数量级,在2 000 W泵浦功率条件下,这种影响仅使振荡光偏离理想分布不到4%,而泵浦功率达到6 000 W时这种偏离则高达20%以上。     

噪声模态单元预判的经验模态分解脉冲星信号消噪

为了改善脉冲星辐射脉冲信号的消噪效果, 提出了一种基于噪声模态单元预判的经验模态分解(EMD) 消噪声方法. 该方法首先利用EMD将含噪辐射脉冲信号分解为一组内蕴模态函数(IMF), 根据IMF系数的统计特性采用局部均方误差准则进行噪声模态单元预判, 并将噪声模态单元置零; 然后对噪声模态单元预判处理后的IMF以模态单元为基本单位进行最优比例萎缩消噪, 从而达到抑制噪声、保留信号的目的. 实验结果表明: 与Sure Shrink小波阈值法、Bayes Shrink小波阈值法和EMD模态单元比例萎缩法相比, 基于噪声模态单元预判的EMD消噪方法可以更有效地去除脉冲辐射信号中的噪声, 同时更好地保留信号突变处的细节信息特征, 在信噪比、 均方误差、峰值相对误差、峰位误差和相位误差等方面都有一定程度的改善. 关键词： 脉冲星信号消噪 经验模态分解 噪声模态单元预判 局部均方误差     

Design and characterization of guided mode resonance filters with the improved structure for facile fabrication

In this study, a guided mode resonance filter with the improved structure for facile fabrication is designed; the properties of the designed filters are simulated by rigorous coupled wave analysis. It is found that the resonance wavelength and spectral linewidth are slightly increased with the increasing of the grating thickness, and seldom changed with the thickness of the grating filling factor, as the parameter error of the grating thickness and the grating filling factor are deviated from the designed value by ±10%, respectively, which are very favorable for simplifying preparation process of the GMR filter.     

The single-longitudinal-mode operation of a ridge waveguide laser based on two-dimensional photonic crystals

An electrically driven, single-longitudinal-mode GaAs based photonic crystal (PC) ridge waveguide (RWG) laser emitting at around 850 nm is demonstrated. The single-longitudinal-mode lasing characteristic is achieved by introducing the PC to the RWG laser. The triangle PC is etched on both sides of the ridge by photolithography and inductive coupled plasma (ICP) etching. The lasing spectra of the RWG lasers with and without the PC are studied, and the result shows that the PC purifies the longitudinal mode. The power per facet versus current and current-voltage characteristics have also been studied and compared.     

Dominant modes of submerged thin cylindrical shells

The relationship between the dominant mode of the submerged thin cylindrical shell and the flexural wave velocity is investigated. The natural frequency corresponding to the vibration mode is obtained as the solution of characteristic equation of thin cylindrical shell. However, it is difficult to estimate the dominant mode, especially if two or more vibration modes are involved. To estimate the dominant mode of a thin shell in vacuo, the concept of “modified bending stiffness” has been introduced. In this paper, the concept of modified bending stiffness is extended to estimate the dominant mode of a submerged thin cylindrical shell. The dominant mode of a submerged thin cylindrical shell is theoretically discriminated from the other mode based on the smallness of the modified bending stiffness of the submerged shell. The validity of our theory is confirmed by a good agreement between theoretical and experimental results on flexural wave velocity.     

依赖强度耦合三光子过程下运动原子最佳熵压缩态的制备

为了研究三光子过程中原子与相干态耦合量子体系信息熵压缩随时间演化规律及原子最佳信息熵压缩态的制备,我们采用全量子理论,推导出运动原子与单模简并三光子依赖强度耦合量子体系的精确解;理论上给出制备原子最佳信息熵压缩态的充分及必要条件,并进行了数值模拟验证。研究结果表明：控制相干态场与原子作用时间,切断相干态场与原子的纠缠,选择二能级原子处于等权重相干叠加态,适当选取相干态场与原子的初始位相,可以制备出原子最佳量子信息熵压缩态;调节光腔中场模结构参量,能够得到连续的量子信息熵压缩态。该研究结果在多光子过程低噪声量子信息处理中具有一定意义。     

小波时-频变换的高强钢丝弹性波传播模态分析

超声导波是近年来桥梁拉索无损检测研究的重要方法之一。针对弹性波在高强钢丝介质中传播的多模态频散问题,采用单点时域波形的小波时频变换进行混叠信号的模态识别分离。通过数值求解Pochhammer频率超越方程,计算得到0~1.5 MHz范围内纵向导波模态理论频散曲线;采用有限元模拟半波正弦脉冲激励导波在钢丝中传播过程,由小波时-频变换得到导波模态分布,并进行了不同腐蚀程度钢丝实验对比分析。结果表明,经小波时-频变换得到的第1、2、3阶纵向导波模态与理论值对应吻合,单点时域波形的小波时-频变换结果能够有效识别高强钢丝中的导波模态;钢丝在无腐蚀状态下,一阶纵向导波模态能量占比达57.74%,随腐蚀程度增加,能量更为集中到一阶纵波模态,二阶模态能量逐渐减小。