毫微秒电磁脉冲在探测地下浅层目标中的应用

由分析毫微秒电磁脉冲在探测地下目标的基本理论,提出了实施方案以及关键部件的设计,研制了有特色的行波天线。实践证明,该方案设计的装置辐射效率高,行波特性好。对埋地深度在1m左右的金属管道,能快速、清晰地显示和打印目标特性。     

毫微秒脉冲发生器设计

利用晶体管的雪崩特性,本文设计制作可以按需要改变输出脉冲宽度的毫微秒脉冲发生器,可获得上升时间Ins、50Ω负载下最大输出脉冲幅度35V、脉冲成形宽度20ns、最大重复频率60kHz的毫微秒脉冲。     

奇妙的毫微微秒和低比特

今天上午，我特别荣幸地在此与你们讲信息技术的奇妙力量，它驱动着全球当前的通讯革命。我演讲的题目是“奇妙的毫微微秒和低比特”。今天全球通讯行业被两个彼此互相独立又互相关联的技术所支配：强有力的技术认知曲线和媒体数字化，认知曲线代表了强有力的关键信息技术。而媒体数字化涉及所有的声音、资料、数据、图形图象信息变换，转换成二进制数字，或比特，或数字编码。这些技术力量与全球通讯市场的开放与私有化相互结合，并且还包括现有和潜在顾客对于新技术产品和服务的需求。众所周知，这是一个庞大的全球通讯行业。朗讯科技公司…     

高压快速脉冲放电特定函数脉冲特性的研究

利用亚纳秒脉冲放电管具有高压快速放电的特点，配以由阳极电容与阴极多级ＬＣ级联网络组成的脉冲形成网络在匹配负载上获得了高压快速高斯函数脉冲；配以由耐高压的高低阻抗线或螺旋带仿真线替代贮能电缆而组成的脉冲形成网络，在匹配负载上获得了高压阶跃函数脉冲。     

Monitor and control of neuronal activities with femtosecond pulse laser

Combined with the fluorescence labeling technique, two-photon microscopy excited with femtosecond pulse laser has become an important tool for neuroscience research. In this research, the calcium signals from neurons in rat cortex slice were monitored by a custom-built two-photon microscopy, and the spontaneous calcium signals and the pharmacological responses as well as the responses to femtosecond pulse laser stimulation were recorded. The results showed that the amplitude of the cal- cium signals increased in direct proportion to the corresponding electrical activities. Glutamate induced a calcium transient, but continuous application resulted in smaller response. Simultaneous monitoring of neuronal populations distinguished the neurons of different microcircuits. The femtosecond pulse laser induced local or global calcium signals in the pyramidal neurons. The approach of interrogation and control of neural activities using femtosecond pulse laser is non-contact, nondestructive, repeatable, and without any additional substrates, which will contribute to the development of neuroscience.     

Preparation of porous microstructures on NiTi alloy surface with femtosecond laser pulses

Porous microstructures on Nickel-Titanium （NiTi） alloy surfaces were prepared by linearly polarized femtosecond lasers with moving focal point at a certain speed. It was found that various novel micro- structures from feather-like ripples to cluster-like porous textures could be formed with increasing laser energy. Particularly, when the laser energy was 400 llJ, a periodic porous metal surface was gen- erated. Measurement of X-ray diffraction showed that the grains on the sample surface were refined through femtosecond laser ablation processes, but the crystal structures still kept their original states. Analysis by X-ray photoelectron spectroscopy revealed that Ni/l＂i on the sample surface was changed with an evident oxidization of titanium element under different laser energies. This investigation pro- vides a new approach to improve the biocompatibility of NiTi-based implant devices.     

Photodissociation/photoionization processes of chlorobromomethane induced by femtosecond laser pulses with pump-probe scheme

The photodissociation/photoionization processes of chlorobromomethane （CH2BrCl） induced by femtosecond laser pulses have been investigated using pump-probe scheme combined with the time-of-flight mass spectra. The dominate photoproducts are observed at different delay time of the pump （400 nm） and probe （800 nm） pulses and the corresponding time-dependence of them is obtained. The results show that the decaying time of the molecule CH2BrCI in the A-band is in the 100 fs. The decaying tendencies of the fragment ions （CH2CI^＋ and CH2Br^＋） and the parent ion （CH2BrCI^＋） are almost the same and the relative ratios of the yields of them keep constant during the delay time of 0 to 150 fs. These facts suggest that the fragment ions come from the fragmentation of the parent ions in excited electronic states. The probabilities to form CH2CI^＋ and CH2Br^＋ are obtained from the relative ratio of the ion intensity and are about 71.6% and 14.2%, respectively.     

Effects of cavity-dispersion noncoaxiality on the generation of ultrabroadband femtosecond pulses

The effects of cavity-dispersion noncoaxiality （CDN） on the generation of ultrabroadband femtosecond pulses in KLM Ti：sapphire laser were investigated theoretically and experimentally. It was predicted that when the laser sub-cavity works near the coaxial operation point, the limitation of CDN on the bandwidth broadening is minimum, which is favorable for ultrabroadband pulse generation. On the basis of this prediction, femtosecond pulses with bandwidth of 650 to 1000 nm were directly generated from a home built KLM Ti：sapphire laser. To our knowledge, they are the broadest bandwidth pulses produced from KLM Ti：sapphire laser with similar oscillator configuration and gain crystal length of 3 mm.     

富勒烯[ 60] 与电子给体电荷转移络合物的特性

通过毫微秒激光光解作用研究了富勒烯[60]电荷转移络合物的特性，在苯腈溶液中，从电子给体(TTF)到富勒烯[60]激发三线态的电子转移反应已被观察到，富勒烯[60]激发三线态的消失和富勒烯[60]阴离子自由基的出现，通过瞬态吸收光谱得到证实。     

新型超宽带脉冲探地雷达接收机的设计与研制

基于等效时间采样原理,提出了一种新型超宽带脉冲探地雷达接收机的设计方法,并研制了实用的超宽带接收机模块,其关键电路包括皮秒级采样脉冲产生电路、肖特基二极管平衡取样门、信号保持与放大电路以及微带魔T结构。该接收机的采样带宽为4 GHz,与理论计算值相一致,采样效率高达40%。实验测试表明,接收机等效采样后重建的基带信号波形与原始微波信号形状吻合度好,证明该接收机具有良好的超宽带特性,满足脉冲探地雷达回波信号接收要求。