Electrochemical,thermal,and photophysical properties of novel two-photon absorption chromophores

Electrochemical, thermal, and photophysical properties of novel two- （BPODPA）, four- （BBPOPA）, and six-branch （TBPOA） triphenylamine chromophores are studied. The decomposition temperature of chro- mophores reaches 373 - 412 ℃. The electrochemical properties is explored by cyclic voltammetry. The ionization potential of chromophores is in the range of 5.14 - 5.18 eV. Excitation at 400 nm reveals emission peaks at 483 - 487 nm and the fluorescence quantum yields are 0.73 - 0.75 in CH2Cl2. Two-photon absorption （TPA） properties of chromophores are measured by nonlinear transmission method. The maximum TPA cross-section values are measured at 758 nm to be 20369 GM （1 GM=10^-50 cm^4 -s/photon） for TBPOA, 7024 GM for BBPOPA, and 1227 GM for BPODPA, respectively. When pumped with 800-nm laser irradiation, chromophores show strong two-photon excited blue-green fluorescence at 502 - 518 nm. These results provide a basis for understanding the electronic and optical properties of the conjugated multi-branch chromoohore in terms of the underlying molecular and electronic structures.     

半导体激光器的功率控制

为满足目前光纤通信领域中半导体激光器功率高精度控制的要求,结合半导体激光器的内部结构及其功率特性,重点研究了半导体激光器(LD)和光电二极管PD的工作原理,并根据激光器LD和光电二极管PD在实际工作状态下的特性参量提出了半导体激光器的高精度功率控制方法; 采用AD8304高动态范围对数放大器设计了一种应用于光学真延时系统中的半导体激光器功率控制电路,并根据AD8304对数放大器的内部结构及工作特性对整个闭环电路系统做了详细分析; 实验测试结果表明,该功率控制电路运行稳定、工作温度范围宽、控制精度高、成本低廉且易于集成,能够广泛适用于大多数半导体激光器中使用。     

纳米氧化锌的紫外自发辐射与受激辐射

纳米结构的氧化锌兼备了宽直接带隙(E_g=3.34eV)、强激子束缚能(60meV)的优良特性,同时又具备了纳米材料独特的微结构与光电功能,可望成为高效率紫外发光二极管以及低阈值紫外半导体激光器的良好材料。以我们的工作为基础,利用不同结构的ZnO作增益介质,概述了低维ZnO纳米材料中的自发辐射与受激辐射过程,观察到了放大的自发辐射(ASE)与受激振荡现象,并讨论了自发辐射、ASE及受激辐射的产生机制。     

基于虚拟仪器和可调谐激光技术的光纤光栅传感系统

提出了一种新颖的基于虚拟仪器(VI)和可调谐激光技术的光纤光栅(FBG)传感系统,利用可调谐激光对由光纤光栅组成的传感器阵列进行波长扫描,实现了多根光栅的复用准静态解调,并结合抖动技术和反馈环结构,使得探测信号在每一根传感光栅中心波长处过零,以提高系统在测定波长偏移时的分辨力。当反馈环工作在闭环状态下时,该系统还可对单根光栅实现动态跟踪锁定,实现单根光栅的动态解调。该传感系统的数据采集采用虚拟仪器技术,通过多通道同时输入输出实现了在线实时解调。实验采用了4根光栅组成传感阵列,获得了静态多根光栅小于1με和单根光栅动态频率10 Hz时3.3 n/εHz的解调分辨力,动态应变范围在850με。     

光纤布拉格光栅法布里-珀罗腔纵模特性研究

分析了光纤布拉格光栅构成的法布里-珀罗（F-P）腔的透射谱特性，讨论了光栅带宽，反射系数相位因子以及腔长对F-P腔透射特性的影响，并对F-P腔随温度和应变的特性进行了分析，然后给出如何设计在光栅中心耦合波长处单模运转的法布里-珀罗腔.并提供了数值模拟结果和实验结果. 关键词： 光纤布拉格光栅 法布里-珀罗（F-P）腔 光纤激光器     

Wide-band double-pass discrete Raman amplifier with reflection of signals and pumps

A wide-band (1530-1610 nm) and high efficient double-pass discrete Raman amplifier is reported. In this Raman amplifier, by using a one-end gilded fiber as the broadband reflector, signals and multi-pump are both reflected to propagate through the gain fiber for a second time. An increase in net gain of more than 150% has been achieved compared with that in the typical co-pumped Raman amplifier. The advantages of this proposed new configuration have been experimentally studied by comparing with the recently existing Raman amplifier configurations.     

分子一阶超极化率溶剂效应的理论研究

基于一维谐振子模型建立了极性溶剂对光学二阶非线性分子一阶超极化率产生影响的简化理论模型,推导出了非线性分子的线性极化率α和一阶超极化率β的表达式. 以对硝基苯胺为例,所建立的理论模型计算结果较好地解释了实验获得的溶剂极性对其分子线性吸收峰波长（λ_p）和β值的影响. 关键词： 二阶非线性 溶剂效应 谐振子     

Biocompatible and stable core/shell drug nanocarrier with high surface-enhanced Raman scattering activity

<正>A novel drug carrier based on SiO_2-coated silver nanoparticle aggregates and antitumor drug is successfully synthesized.The surface-enhanced Raman scattering(SERS) spectra of the antitumor drug in living cells are obtained.By using silver nano-aggregates as SERS substrates instead of dispersed silver particles, a great improvement of SERS signal intensity is achieved.It is found that the chemical stability of the drug carrier can also be increased with the existence of SiO_2 shell.The adsorbing effect between antitumor drug 9-aminoacridine(9AA) and silver particles is investigated to optimize the SERS signal. The core/shell structure of the drug carrier is characterized by ultraviolet-visible(UV-Vis) spectroscopy and transmission electron microscopy(TEM) pictures.The experimental results show that the drug carrier offers biocompatibility,stability,and high SERS activity,holding the potential for realizing the intracellular drug tracing.     

Mechanism of Spatiotemporal Distribution of Laser Ablated Materials

Interaction between subsequent laser and ablated materials in laser processing changes the laser spatiotemporal distribution and has influences on the efficiency and quality of laser processing. The theoretical and experimental researches on transportation behaviour of ablated materials are provided. It is shown that the velocity distribution of ablated materials is determined by ablation mechanism. The transportation behaviour of ablated materials is controlled by diffusion mechanism and light field force during laser pulse duration while it is only determined by diffusion mechanism when the laser pulse terminates. In addition, the spatiotemporal distribution of ablated materials is presented.     

集成马赫-曾德尔热光耦合器的可调谐振环优化设计

根据耦合模理论,推导出可调谐光波导谐振环的光强和相位传递函数的表达式,并分析了可调谐谐振环的传输特性.结果表明,谐振环中集成的马赫-曾德尔耦合器的参量设定和调谐方式直接影响谐振环的谐振频率移动范围和调制功率.通过改变耦合器参量对谐振环进行优化设计,在中心波长为1550 am附近,谐振环半径2 cm,传输损耗0.08 dB/cm的情况下,实现了清晰度和最佳谐振深度的调谐,谐振频率的移动范围低于0.027 GHz,降低了谐振环对频率调制器的调频要求,同时降低了耦合器的调制功率.