Generation of Femtosecond Laser Pulse at 1053 nm with Contrast of 10-11 by Optical-Parametric Amplification

A high contrast 1053nm femtosecond laser pulse with free background is demonstrated based on non-collinear optical-parametric amplification （NOPA）. By permuting the signal and idler in two stages of NOPAs, 48.2fs, 62 μJ laser pulse at 1053nm with contrast ratio of 2.3 ×10^-11 is obtained within the time scale of sub-5 ps. The beam quality factors M2 for tangential and sagittal directions are 1.59 and 1.30, respectively. This work not only proves a feasible way to generate a clean femtoseeond laser pulse but can also be employed as an ideal frontend for ultrashort ultrahigh intensity Nd：glass-based laser systems.     

Terahertz electromagnetic waves emitted from semiconductor investigated using terahertz time domain spectroscopy

Ultrafast electromagnetic waves radiated from semiconductor material under high electric fields and photoexcited by femtosecond laser pulses have been recorded by using terahertz time domain spectroscopy (THz-TDS).The waveforms of these electromagnetic waves reflect the dynamics of the photoexcited carriers in the semiconductor material,thus,THz-TDS provides a unique opportunity to observe directly the temporal and spatial evolutions of non-equilibrium transport of carriers within sub-picosecond time scale....     

时间尺度上三点边值问题正解的存在性(英文)

利用锥不动点定理得到了时间尺度上非线性三点边值问题一个和两个正解的存在性.     

在时间尺度上研究带有脉冲的泄漏时滞细胞神经网络反周期解的动态特征

在时间尺度上,通过使用叠合度理论中的连续定理和微分不等式技巧,研究带有脉冲的时变泄漏时滞细胞神经网络模型的反周期解,获得了一些使带有脉冲的时变泄漏时滞细胞神经网络模型的反周期解存在和全局指数稳定的充分条件,并将以前的结论在时间尺度上做了扩展.     

时间尺度上脉冲动力系统的实用稳定性

对时间尺度上脉冲动力系统进行研究,利用Lyapunov类函数和比较原理,得到这类系统实用稳定性的充分条件.     

An Island Coalescence Scenario for Near-Earth Current Disruption in the Magnetotail

A current disruption and dipolarization scenario associated with island coalescences in the near-Earth region is proposed. The thin and elongated current-sheet built up during the growth phase is unstable due to a tearing mode instability that leads to formation of multiple magnetic islands （or magnetic flux ropes in the three dimensional case） in the near-Earth region. The growth rate of the tearing mode shoual be different in different locations because the rate is in general determined by the external driving force and the local plasma sheet properties. When the rate of the magnetic reconnection in the mid-tail region around 20RE is much larger than that in other locations, the strong bulk earthward flows resulting from the fast reconnection in the mid-tail drive the earthward convection and the coalescence of the magnetic islands. Consequently, the cross-tail current in the near-Earth region is suddenly disrupted and the geometry of the magnetic field changes from tall-like to dipolar-like in the ideal time scale. This proposed scenario is tested by Hall MHD simulation and is compared with the observations.     

Vaidya—Schwarzschild—de Sitter时空中时间尺度变换的纯规范势

同稳态时空一样，动态Ｖａｉｄｙａ－Ｓｃｈｗａｒｚｓｃｈｉｌｄ－ｄｅ Ｓｉｔｔｅｒ时空中的Ｈａｗｋｉｎｇ效应可看作时间尺度变换下的补偿效应，补偿场纯规范势的一个分量表征黑洞温度，另一个表征黑洞温度变化率。     

物理世界的空间尺度和时间尺度

 你知道现代科学所知的物理世界在空间和时间尺度上有多大吗?请看图1、图2中关于一些典型物理现象的空间尺度和时间尺度的图示.     

实验室天体物理学中的标度变换

采用当前最先进的激光装置,可以获得与天体物理过程中相同或相似的条件,因此实验室天体物理学已成为激光等离子体物理学家位深感兴趣的研究内容,也同时成为天体物理学家所关注的问题,然而,激光等离子体为微米级的空间尺度和纳秒或更短的时间尺度,而天体物理的对象则为宇宙学的极大的时间与空间尺度,文章讨论了在物理上和实际操作上将这两种表面上存在巨大差异的物理过程对应起来,从而为利用激光等离子体研究天体物理过程中提供了可能性。     

时间尺度上一类二阶非线性动力系统的振动性判据

研究了时间尺度T上一类二阶非线性中立型变时滞泛函动力系统的振动性,通过引入2个不同的Riccati变换,借助时间尺度上的微积分理论,并结合不等式技巧,得到了该系统振动的2个新的准则,推广、改进和丰富了现有文献中的结果.