聚(9,9-二辛基芴)和聚(9,9-二辛基芴-共-苯并噻二唑)的光物理特性的理论和实验研究

通过比较分析聚(9,9-二辛基芴)(PFO)和聚(9,9-二辛基芴-共-苯并噻二唑)(F8BT),对半导体聚合物的光物理特性进行了系统研究. 量子化学计算显示,苯并噻二唑单元的引入促进了链内电荷转移(ICT),调节了聚合物的电子跃迁机制. 瞬态吸收测定表明,在单分散系统中的受激PFO衰减时主要表现为链内激子弛豫.在F8BT溶液中,ICT状态出现,并参与到激发态的弛豫过程中. 凝聚相中PFO和F8BT的弛豫过程加速和显示了在高激发强度下具有显著的激子湮灭行为. 在相同的激发强度下,F8BT的平均寿命长于PFO,有助于实现良好的电荷离域.     

γ-LiAlO2上a面ZnO薄膜的光谱特性研究

利用激光脉冲沉积(PLD)技术在(302)γ-LiAlO₂衬底上成功生长了非极性的a面(1120)ZnO薄膜，光致发光谱(PL)带边发射峰半峰宽仅为115meV.研究了非极性ZnO薄膜光谱特性的面内各向异性，发现随着入射光偏振方向改变，在偏振透射光谱上，吸收边移动了20meV，这与A、B激子和C激子的能量差一致；而在拉曼光谱上，激发光偏振方向的改变导致E₂模式的强度发生明显改变.     

混合气体声复合弛豫频谱的解析模型

为研究声传播和分子多模式振动能量弛豫的相互关系,本文提出了一种混合气体声 复合弛豫频谱的解析模型.该模型从振动模式微观能量转移及其耦合形成宏观弛豫过程两个角度, 分析了依赖于声频率的混合气体有效热容.并通过求解振动模式能量转移的通用弛豫方程, 最终得到可同时体现主副弛豫过程的声弛豫吸收和声频散的解析结果.仿真结果表明, 对于CO₂, CH₄, N₂和O₂组成的多种混合气体, 该模型的声吸收谱与实验数据相符,峰值误差在1%以内,且反映了多振动模式形成的 声复合弛豫吸收谱上通常仅会显现1-2个吸收波峰的物理现象.与已有模型相比, 本解析模型可直接求出混合气体声弛豫频谱上特征点的解析形式,并利于对其进行定性定量分析. 从而为研究声传播特性与气体分子弛豫特性的相互关系提供了一个有效理论模型.     

聚合物中产生双激子的新通道

由于聚合物中的双激子能产生新奇的光致极化反转现象,如何在聚合物中产生双激子变成为一个重要的研究课题.在现在已知的产生双激子的通道以外,提出了一条新的通道:双电子激发,并用动力学方法研究了此通道产生双激子的弛豫过程(包括键结构畸变和电子态的方面),确定了双激子形成和极化反转所需要的时间. 关键词： 聚合物 双激子 通道     

非晶态聚合物主转变弛豫峰与玻璃化转变过程的相关性研究

从弛豫理论出发,在不同的时效时间和不同降温速率下,测量了非晶聚合物PVC玻璃化转变过程中与时间参量密切相关的α峰峰温(T_α)的响应关系,得出以下结论:1)玻璃化转变温度(T_g)一般是指非晶态聚合物热平衡态与非平衡态的温度转变点(T_t),是温度变化造成的热弛豫过程的直接结果,而α内耗峰是在动态力学测量过程中得到的聚合物玻璃态与高弹态(橡胶态)的分界点处的力学弛豫过程,表现为动态模量锐变过程,是非晶态聚合物热平衡态下的特征内耗峰.两者都与非晶态     

近场光学显微镜研究CdS0.65Se0.35纳米带空间分辨光致荧光谱

通过热蒸发方法成功制备出CdS_0.65Se_0.35纳米带，得到的纳米带表面光滑，宽度厚度均一，表现出很高的结晶质量.使用近场光学显微镜对纳米带室温下的带边荧光波导和光致荧光近场光谱进行研究.发现CdS_0.65Se_0.35纳米带呈现良好的光波导的特性；同时通过近场光学显微镜得到的空间分辨光谱，发现随着传播距离的增大，纳米带的光致荧光光谱有持续的红移现象.这种光谱红移现象是带间跃迁过程中带尾态的吸收效应引起的，并作了光谱带尾态吸收的理论模拟与实验结果进行比较.光波导传输过程中光谱的变化反映了信息在整个传导过程中的情况，体现了信息传递过程中的稳定性和有效性.三元合金材料CdS_0.65Se_0.35纳米带的波导和光谱性质研究，对于其他组分可调的三元合金纳米结构的制备和研究，及发展新型的纳米功能器件有重要意义.     

激子旋转弛豫对低掺杂卟啉侧链聚合物荧光衰变过程的影响

利用激子旋转扩散理论研究了一类低掺杂卟啉侧链聚合物中卟啉侧链基团的旋转对其发光动力学过程的影响.研究表明,卟啉侧链基团的旋转行为是导致激发态无辐射能量弛豫的重要途径.基团旋转越容易,能量弛豫速度越快,这可导致一个快速的荧光衰变动力学过程.在卟啉低掺杂浓度和聚合物分子链间距离较大的情况下,卟啉侧链基团的旋转成为影响荧光寿命和发光效率的主要因素.对实验测得的两种样品的荧光弛豫过程进行了拟合,理论结果与实验结果符合较好. 关键词： 激子旋转弛豫 瞬态荧光 卟啉侧链聚合物     

磁场作用下的有机电致发光

分别制备了荧光器件ITO/NPB/Alq₃/LiF/Al和磷光器件ITO/NPB /CBP: Ir（ppy）₃/BCP/Alq₃/LiF/Al, 测试了50 mT磁场作用下器件的I-V和L-V特性. 与零磁场相比荧光器件和磷光器件的效率分别增加了44%和7%. 从有机电致发光的机制出发对该现象进行了解释, 认为外加磁场可以使三重态激子发生塞曼分裂, 进而在荧光器件中引起了三重态激子T     

超高泵浦功率下的Xe(6p[1/2]0, 6p[3/2]2, 和6p[5/2]2)原子的能量转移过程

本文研究了Xe(6p[1/2]₀, 6p[3/2]₂, and 6p[5/2]₂)原子在聚焦条件下的动力学过程. 激发能级的原子密度在聚焦条件下会显著地增加,因此两个高激发态原子之间的energy-pooling碰撞的概率也会增加. 这种energy-pooling碰撞主要有三种类型. 第一种类型为energy-pooling碰撞导致的电离. 一旦将激发激光聚焦,就可以从侧面的窗口观察到非常明显的电离现象,不论激发能级是6p[1/2]₀、6p[3/2]₂或6p[5/2]₂能级. 这种电离的产生机理是energy-pooling电离或者一个Xe^*原子再吸收一个光子产生电离. 第二种类型为跨越较大能极差的energy-pooling碰撞. 当激发能级为6p[1/2]₀能级的情况下,两个6p[1/2]₀原子碰撞会产生一个5d[3/2]₁原子和一个6s''[1/2]₀原子. 第三种类型为跨越较小能级差的energy-pooling碰撞. 以5个二次产生的6p能级为上能级的荧光强度都变得更强,并且这些荧光的上升沿都变得更陡峭. 产生这些6p原子的主要机理是energy-pooling碰撞并非简单的碰撞弛豫. 基于理想气体原子之间的碰撞概率公式,推导出两个6p[1/2]₀原子的energy-pooling碰撞速率为6.39x10⁸s^-1. 此外,6s原子在聚焦条件下的密度也会增加. 因此所有的荧光曲线会因为辐射俘获效应而出现非常严重的拖尾.     

六硝基菧溶液的νs(NO2)激发及弛豫过程的相干反斯托克斯拉曼光谱

研究含能材料的振动激发和弛豫过程能深入理解含能材料的超快动态响应过程. 利用亚皮秒分辨的相干反斯托克斯拉曼(CARS)技术,实验直接观察基态的六硝基菧溶液中ν_s(NO₂)激发峰位于1385 cm^-1,弛豫时间为0.38和8.5 ps. 飞秒CARS实验观察到相应的拍频现象.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.