Active long pulse shaping technique of pulsed CO2 laser using multi-pulse discharge control

We describe the pulse forming of pulsed CO₂ laser using multi-pulse superposition technique. Various pulse shapes, high duty cycle pulse forming network (PFN) are constructed by time sequence. This study shows a technology that makes it possible to make various long pulse shapes by activating SCRs of three PFN modules consecutively at a desirable delay time with the aid of a PIC one-chip microprocessor. The power supply for this experiment consists of three PFN modules. Each PFN module uses a capacitor, a pulse forming inductor, a SCR, a high voltage pulse transformer, and a bridge rectifier on each transformer secondary. The PFN modules operate at low voltage by driving the primary of HV pulse transformer. The secondary of the transformer has a full-wave rectifier, which passes the pulse energy to the load in a continuous sequence.We investigated various long pulse shapes as different trigger time intervals of SCRs among three PFN modules. As a result, we could obtain laser beam with various pulse shapes and durations from about 250 to 1000 μs.     

The Analysis and Improving of the Microwave Exciter in the Lower Hybrid Wave System

When we carry out lower hybrid wave heating and current driving plasma experiment at tokamak, we need mega-watt order of microwave power. The microwave signal at frequency of 2450 MHz is generated by a microwave exciter. According to the experiment＇s demands, the microwave exciter must provide output power of 1.5～ 2. 5 W with stabilized frequency and amplitude tobe used as the klystron input. Being amplified by the klystron, the microwave signal is transmitted through the transmitting system to the antenna and is emitted into the HL-2A tokamak. So we can see that the microwave exciter＇s function is very important to the lower hybrid wave heating and current driving plasma experiment.     

甲基对硫磷的快速测定及电化学性质

研究了杀虫剂甲基对硫磷的电化学性质。在pH10．38的Bdtton—Robinson缓冲溶液中，采用微分脉冲溶出伏安法在悬汞电极上得到一个还原峰，峰电位为-0．5V(vs．Ag/AgCl)，本工作对实验条件进行了深入的研究，结合线性扫描伏安法等手段。研究了体系的电化学行为。实验表明，甲基对硫磷在汞电极上具有吸附性，电极反应具有不可逆性。该法用于水果及水样中甲基对硫磷残余量的测定，结果满意。     

单光子态的产生与测量

报道了通过自发参量下转换产生单光子态的实验研究,使用中心波长425 nm的飞秒脉冲泵浦Ⅰ类非共线相位匹配的BBO晶体,在实验上得到单光子计数率为2.978×10-4,并分析了实验中的相关问题.     

全光纤脉冲压缩器的理论及实验研究

对色散位移光纤＋普通单模光纤构成的全光纤脉冲压缩器进行了理论分析，分析了压 缩效果与光纤参数及输入脉冲参数的关系；对不同中心波长和脉宽的主动锁模光纤激光器的 输出脉冲进行了压缩实验，均得到了近变换限Sech的压缩脉冲，实验结果与理论分析一致. 关键词： 全光纤脉冲压缩器 压缩因子 基座能量 主动谐波锁模光纤 激光器     

Microwave-accelerated Claisen rearrangements of allyl tetronates and tetramates

[3,3]-Sigmatropic rearrangements of allyl tetronates and allyl tetramates to give 3-allyltetronic or -tetramic acids, respectively, proceed within 20-60 min under microwave irradiation (300 W, 130-190 °C). Consecutive (homo)sigmatropic [1,5] H-shifts such as oxa-ene reactions are promoted less effectively, which allows the isolation of Claisen intermediates of sigmatropic domino sequences, in contrast to conventional heating.     

Application of polymer-supported triphenyl phosphine in the palladium-catalyzed cyanation reaction under microwave conditions

A variety of aryl nitriles were prepared in excellent yields from the palladium acetate catalyzed coupling of aryl halides with Zn(CN)₂ using polymer-supported triphenyl phosphine as the ligand and dimethylformamide as solvent under microwave irradiation conditions.     

Rare earth photoionization study by the resonant microwave cavity technique

Photoconductivity spectra of rare earth-doped insulating materials are measured using the resonant microwave cavity method. This technique is based on the detection of the cavity Q-factor changes induced by irradiation of the sample (inserted in the cavity) by a pulsed tunable laser. Results obtained with Lu₂(SiO₄)O:Ce³⁺ and BaF₂:Eu²⁺ are presented and discussed. Photoionization thresholds at 400 nm (3.1 eV) and 310 nm (4.0 eV) are measured for Lu₂(SiO₄)O:Ce³⁺ and BaF₂:Eu²⁺, respectively.     

Physical Interpretation of the Motion of a Laser Pulse within the Framework of the Four-Oscillator Model

A physical multidimensional local model of the propagation process of a laser pulse in air having no analogy to famous models in laser physics is constructed. It is based on the representations of classical wave mechanics characteristic of the theory of scalar wave fields.     

光参量啁啾脉冲饱和放大的增益稳定性

 光参量啁啾脉冲放大（OPCPA）在饱和放大区存在一个增益稳定点，据此设计了一个输出稳定的三级OPCPA系统；第一、二、三级分别选用准相位匹配的周期极化钛氧磷酸钾（PPKTP）晶体、LBO晶体和KDP晶体作为增益介质。饱和放大时，增益随泵浦光强度变化时的增益输出稳定性明显改善，在泵浦光强度抖动低于6%的情况下，各级光参量放大器OPA输出的增益抖动小于1%。前级采用准相位匹配的PPKTP晶体作为增益介质，在远低于破坏阈值的30MW/cm²的泵浦功率密度下，可得到2×10⁵的饱和放大增益和20%的能量转换效率。