PROBING HIDDEN POLYMERIC INTERFACES USINGIR-VISIBLE SUM-FREQUENCY GENERATION SPECTROSCOPY

Understanding the molecular-level processes underlying interfacial phenomena is important in the area of adhesion. We briefly introduce IR-visible sum-frequency generation spectroscopy (SFG) using a total-internal-reflection geometry for the study of polymer-air, polymer-solid, and polymer-polymer interfaces. The following examples, predominantly of work done in our lab, illustrating differences in molecular structure and dynamic properties at interfaces are presented: the air- and solid-interface structure of an amorphous polystyrene (PS) and a semicrystalline polymer with side-chain crystallinity, poly(octadecyl acrylate) (PA-18); structure of a polymer-polymer interface between thin films of a semicrystalline polymer with side-chain crystallinity, poly(vinyl-N-octadecylcarbamate- co-vinyl acetate), and an amorphous PS; thermal order-to-disorder transitions of the air and solid interface of PA-18, and the interface of this polymer with PS; and dynamic surface-relaxation studies of a rubbed PS film.     

Precipitation and stability of reversed austenite in 9Ni steel

A new method was used to analyze the factors affecting the precipitation of reversed austenite during tempering. The samples were kept at various tempering temperatures for 10 min and their length changes were recorded. Then, the precipitation of reversed austenite which led to the length reduction was shown by thermal expansion curves. The results show that the effects of process parameters on the precipitation of reversed austenite can be determined more accurately by this method than by X-ray diffraction...     

石英晶体最大双折射率色散特性的椭偏测量

为了测量石英晶体最大双折射率的色散特性,在椭偏光谱仪的水平透射测量模式下,通过对确定厚度的石英波片相位延迟量的精确测量,计算出了石英晶体的最大双折射率值,并进行了误差分析。结果表明:这种方法光路简单、操作方便,屏蔽了光源的不稳定性;双折射率测量精度达到了10-6,比连续偏光干涉法的测量精度提高了1个数量级;实现了对石英晶体的最大双折射率色散特性的连续光谱测量;此方法对其它双折射晶体材料的双折射率色散特性的研究也同样适用。     

测量超短激光脉冲啁啾阶数及量值的一种新方法

提出了一种测量超短激光脉冲啁啾阶数及量值的新方法。根据二次干涉自相关(IAC)包络比值对啁啾有很高灵敏度的特性,通过对IAC包络比值进行分析计算获得判断啁啾阶数的方法,并得到包络比值中央半宽与啁啾量值间的对应关系。采用IAC二次谐波检测系统对加浓染料激光器输出的脉冲进行测量,结果表明,被测超短激光脉冲含有平方啁啾,啁啾参数为0.80,实现了对超短激光脉冲啁啾阶数及量值测量。     

提高CCD测量精度的方法研究

提出一种大幅提高CCD的测量精度的方法。将像素间距为H的CCD器件像素行沿与被测边缘垂直方向成α角度摆放时,单线阵CCD的最大测量误差减小为Hcosα;N个线阵CCD等距错排并以α角度斜放,最大测量误差将减小为(Hcosα)/N;当列间距为h的面阵CCD沿被测对象轴向斜放时,最大测量误差减小为hsinα。分别采用单CCD和双CCD,对直径为5.000、8.000和12.000mm的3个标准杆件的直径进行了测量,结果表明,双CCD斜放可获得更高的测量精度。     

相干组束自成像腔腔型设计理论研究

为了更合理地设计光纤组束谐振腔,针对自成像共振腔,用傅里叶光学理论对其进行了分析,并讨论了3种关键元件——傅里叶透镜、滤波器与输出镜的选取方法;提出了用MATLAB进行数值模拟进而得出空间滤波器透过率函数的计算方法.并以2个半径为55 mm且相距为240 mm的圆形光场为例,模拟了经过傅里叶变换后频谱面上的振幅分布和相位分布情况,通过比较相位,得到了两光场的同相位分布图像.同时,根据矩阵传输理论对腔体进行了分析,得到了自成像无源共振腔稳定振荡的必要条件,及振荡光光纤耦合效率最高的条件.     

衍射光学元件在现代光学成像系统中的应用

衍射光学元件是利用表面浮雕结构对光波进行调制的元件．通过对比折射元件分析了衍射元件用于成像系统的特点,如任意相位分布、特殊色散等性质．探讨了衍射光学元件在现代成像系统中的应用优势,它与折射元件相结合可以实现许多传统光学系统不能达到的目标．     

三维超材料的非线性电、磁响应特性

理论研究了埋入在非线性介质中的由金属线和谐振环构成的具有三维周期性结构的超材料的有效电、磁响应,计算了该种超材料的有效磁导率和介电常数实部和虚部随外场的变化关系.结果表明,这种超材料有效磁导率和介电常数的实部对外磁场的响应具有回滞效应.在一定条件下,这种结构的属性可在右手材料、电单负材料与磁单负材料之间转换,且这种转换可适当选择在某些特定频率范围内的外磁场强度的方式控制.     

吸收对准相位匹配线性电光效应的影响(英文)

研究吸收对准相位匹配线性电光效应的影响,得到适用于吸收介质的准相位匹配线性电光效应的耦合波方程及其解析解.计算结果表明,吸收不但削弱光的强度,且影响o光与e光之间的电光耦合.当o光与e光的吸收系数不同时,由于它们之间的电光耦合,总输出光强随外加电场变化而变化.研究结果可用于吸收介质的电光器件设计.     

Study on the characteristics of erbium-doped waveguide ring laser

A theoretical model of the erbium-doped waveguide ring laser is established according to the theory of erbium-doped waveguide amplifier and the transmission matrix of waveguide directional coupler. The influence of bend radius, coupling coefficient and doped erbium ion concentration on the characteristics of waveguide ring laser is investigated. It is shown that due to the co-action of waveguide bend loss and other relevant loss there is an optimal bend radius which can provide simultaneously low threshold pumping power and high laser light output power. As one part of the resonator’s loss, the laser light coupling coefficient of directional coupler has an impact on the laser property. The analysis indicates that the laser achieves the high output power when the coupling coefficient is about 0.2. The threshold pumping power is the minimum when the doped erbium ion concentration is 0.85×10²⁶ m⁻³. Increasing the concentration of doped erbium ions will enhance the output power of laser light as long as the concentration doesn’t introduce remarkable up-conversion effect. The results give a good theoretical basis for the design and fabrication of erbium-doped waveguide ring laser devices. Supported by the National Natural Science Foundation of China (Grant No. 60807015), the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 200801411037), the Young Teacher Cultivation Foundation of Dalian University of Technology (Grant No. 893210) and Doctor Start-up Foundation of Dalian University of Technology (Grant No. 893322)