飞秒脉冲时空变换整形技术

飞秒激光脉冲通过时空变换技术将时域信息变换到空域，通过空域的处理再返回到时域，是实现飞秒激光脉冲整形、测量和控制的一项重要技术。在应用方面，可产生各种所需要的波形．已广泛应用在飞秒化学、信号处理、安全通信、生物学和医学成像等方面。介绍了飞秒时空变换脉冲整形的几种方法。

不等间距达曼型滤波器的飞秒脉冲时空变换整形与识别技术

研究了以不等间距达曼（Dammann）型滤波器为模板的飞秒激光时空变换与识别技术。优化设计出不等间距多脉冲达曼型滤波器，并在高斯光谱分布的模拟中讨论产生的超快时域多脉冲平均度和光谱平面上调制周期重复数的相关性。给出了频率分辨光开关法（FROG）技术识别超快时域两脉冲的实验结果。

Analysis of an ultrashort pulsed finite beam diffracted by volume gratings

We obtain analytical solutions of the coupled wave equations that describe the Bragg diffraction of ultrashort pulsed finite beams by a thick planar grating, using two-dimensional coupled wave theory. The diffraction properties for the case of an ultrashort pulsed finite beam with Gaussian profiles in both the time and spatial domains are investigated. The spectral bandwidth of the diffracted beam, the Bragg selectivity bandwidth and the diffraction efficiency of the volume grating are influenced by the geometry parameter and the input bandwidth. Therefore extra attention should be paid to designing optical elements based on volume gratings for use with ultrashort pulsed waves in applications of pulse shaping and processing.

基于光纤环形镜的全光脉冲整形器

提出了一种基于光纤环形镜的全光脉冲整形器。该全光脉冲整形器利用波分复用器将控制光脉冲引入光纤环形镜中，控制光脉冲由于交叉相位调制在信号光上产生了非线性附加相移。信号光在耦合器中发生干涉，经过整形的信号光脉冲从脉冲整形器的出射端出射，信号脉冲的波形由非线性附加相移的波形决定。实验中．利用对控制脉冲光谱整形和啁啾展宽的方法来对控制脉冲进行时间脉冲的整形，该全光脉冲整形器实现了对单纵模激光的脉冲整形，同时实现了飞秒脉冲和单纵模整形脉冲的精确同步。在理论上数值计算了该全光脉冲整形器的输出特性，理论计算结果和实验结

基于孔径耦合带状线的激光脉冲整形系统

实现了一种新型的激光脉冲整形系统，该系统使用了一个由孔径耦合带状线（ACSL）电脉冲整形器驱动的电光调制器。一个电脉冲整形器由两条通过其公共接地板上的耦合孔径发生耦合作用的带状传输线所组成的四端口装置。更换具有不同耦合孔径的公共接地板，该电脉冲整形发生器可以具有150ps时间结构的任意整形电脉冲。将任意整形的电脉冲输入到电光调制器上，就可以得到任意整形的激光脉冲。利用该系统，激光脉冲整形系统能够产生具有150ps前后沿，1～3ns脉冲宽度可调、高对比度、光滑过渡以及任意整形的激光脉冲。

高功率激光装置前端系统激光脉冲的时间整形及修正技术

针对激光惯性约束聚变实验研究对高功率激光驱动器前端系统复杂时间形状种子激光脉冲的需求, 应用孔径耦合带状线集成波导整形系统设计了满足需要的前端整形激光脉冲。用一种新方法精确计算了孔径耦合带状线电脉冲整形器的耦合系数和孔径宽度的数值关系, 并针对高衬比度整形激光脉冲的需求, 提出了高衬比度双极型集成波导整形系统方案。由该系统可以得到100 ps脉冲前沿、1～3 ns脉冲宽度可调、高衬比度(大于100∶1)、光滑无纹波调制、可精确满足神光II八路及第九路装置需求的前端整形激光脉冲。

整形激光脉冲与激光探针同步技术

实现了应用于神光Ⅱ装置中的高精度整形激光脉冲与激光探针同步方案。在该方案中,激光探针经硅光导开关进行光电转换之后作为激光脉冲整形单元的触发信号,使激光脉冲整形单元,输出与激光探针同步的整形激光脉冲。为了降低由于触发信号不稳定引起的时间晃动,在光电转换之前放大激光探针,以调整激光脉冲整形单元触发信号的幅度。在神光Ⅱ装置中实现了整形激光脉冲与激光探针小于4.5 ps(均方根)的时间同步精度。

Generation of 1.5-12 ns width-tunable 532 nm pulses by adopting laser-induced plasma shutter technique

The pulse-shaping technique has found widespread applications in nonlinear optics and material processing. Experimental research on laser-induced plasma shutter to control the 532 nm pulse width is conducted. The impacts of the total pulse output energy on pulse compression are investigated, and a useful conclusion can be drawn that there exists an optimal value of pulse energy at which the shortest output pulse of 3.23 ns can be obtained without a device for delay-time. Once the device for delay-time is employed to change the optical differences between two laser paths, the pulse width can be further shortened to 1.51 ns. In short, the 1.5-12 ns width-tunable 532 nm laser pulses have been obtained by adopting the laser-induced plasma shutter technique. (C) 2007 Elsevier GmbH. All rights reserved.

Spectral shaping of femtosecond pulses with a prism-waveguide coupler

We report a novel technique for spectral shaping of femtosecond pulses employing a prism-waveguide coupler (PWC). It is demonstrated that the PWC is capable of producing a frequency-dependent loss with greater attenuation at the peak of the spectrum profile of femtosecond pulses than in the wings, which is especially useful for compensation for gain narrowing in most chirped-pulse amplification laser systems.

Multiphase technique improves mud-pulse velocity calculations

Measurement while drilling (MWD) has become a popular survey technology to monitor directional data, drilling data, formation evaluation data and safety data in the world. And closed loop drilling shows promise in recent years. Obviously, the method of tr

Detection and Characterization of Long-Pulse Low-Velocity Impact Damage in Plastic Bonded Explosives

Damage not only degrades the mechanical properties of explosives, but also influences the shock sensitivity, combustion and even detonation behavior of explosives. The study of impact damage is crucial in the vulnerability evaluation of explosives. A long-pulse low-velocity gas gun with a gas buffer was developed and used to induce impact damage in a hot pressed plastic bonded explosive. Various methods were used to detect and characterize the impact damage of the explosive. The microstructure was examined by use of polarized light microscopy. Fractal analysis of the micrographs was conducted by use of box counting method. The correlation between the fractal dimensions and microstructures was analyzed. Ultrasonic testing was conducted using a pulse through-transmission method to obtain the ultrasonic velocity and ultrasonic attenuation. Spectra analyses were carried out for recorded ultrasonic signals using fast Fourier transform. The correlations between the impact damage and ultrasonic parameters including ultrasonic velocities and attenuation coefficients were also analyzed. To quantitatively assess the impact induced explosive crystal fractures, particle size distribution analyses of explosive crystals were conducted by using a thorough etching technique, in which the explosives samples were soaked in a solution for enough time that the binder was totally removed. Impact induces a large extent of explosive crystal fractures and a large number of microcracks. The ultrasonic velocity decreases and attenuation coefficients increase with the presence of impact damage. Both ultrasonic parameters and fractal dimension can be used to quantitatively assess the impact damage of plastic bonded explosives.

Effects of superimposed pulse bias on TiN coating in cathodic arc deposition

Orthogonal designs are used to investigate the main factors when doing experiments in which pulse bias is superimposed on d.c. bias during cathodic are deposition of TiN. Pulse peak, duty cycle, frequency, direct voltage, are current and pressure all are investigated when coating TiN on HSS substrates. Roughness, surface micrograph, microhardness and thickness are tested. By analysis of variance, it is shown that pressure and frequency are the main factors. R-a and droplet density of the film with (d.c. + pulse) bias decrease. A simple explanation for the result is suggested.

Thermal Decomposition of 1,2-Dichloroethane in a Single-Pulse Shock Tube

在单脉冲激波管上,研究了1,2-二氯乙烷的热裂解.实验的激波条件为:温度区间1020 K＜T＜1190 K, 压力: P=0.12 MPa,实验时间τ=0.5 ms;实验气体为1,2-二氯乙烷稀释于Ar气中(3.95 mmol/L).以4-甲基-1-环己烯作为对比速率法实验的内标物,用4-甲基-1-环己烯开环反应的速率常数k=1015.3exp(-33400/T) s-1,以及从其产物的浓度推定出实验温度.经激波加热后的实验气体的终产物用气相色谱分析出主要成分为C2H3Cl,指示出主要反应通道为β消去反应.如把所有产物C2H3Cl都归于β消去反应,则可推定出表观之反应速率常数k1a=5.0×1013exp(-30000/T) s-1.对于由C-Cl键断键反应引发的链反应的可能影响做了分析研究.用了一种简便分析可推知在实验的温度范围内的低端(1020 K)链反应的影响可以忽略,而在其高端(1190 K)链反应将给出10%的终产物C2H3Cl的附加浓度,获得真实的β消去反应速率常数则必须把这部分予以扣除.经过这样的校正之后,最后得到CH2ClCH2Clβ消去反应速率常数为k1c=2.3×1013exp(-29200/T) s-1.