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Electron plasma induced by a focused femtosecond pulse (130 fs, 800 nm) in dielectric materials (Soda Lime glass, K9 glass, and SiO2 crystal) is investigated by pump-probe shadow imaging technology. The relaxation of the electron plasma in the conduction band is discussed. In SiO2 crystals, a fast self-trapping process with a trapping time of 150fs is observed, which is similar to that in fused silica. However, in Soda Lime glass and K9 glass, no self-trapping occurs, and two decay processes are found: one is the energy relaxation process of conduction electrons within several picoseconds, another is an electron-hole recombination process with a timescale of lOOps. The electron collision time T in the conduction band is also measured to be in the order of 1 fs in all of these materials.  相似文献   
2.
The Carrier-Envelope Phase of Focused Few-Cycle Laser Pulses   总被引:1,自引:0,他引:1       下载免费PDF全文
The Gouy phase shift modulates the carrier-envelope phase of a focused few-cycle laser pulse. We investigate the variations of the carrier-envelope (CE) phase of a pulsed Gaussian beam on and off the axis by the first-order approximation and numerical calculation. The CE phase undergoes a π shift from minus infinity to infinity, and it changes fastest with distance at the focus. The variation of CE phase on propagation distance is nearly independent of pulse duration At when At is greater than lO fs and the first order approximation fits this result very well. The maximum difference of CE phase between a pulse with duration of one cycle and the result of first-order approximation is 0.09.  相似文献   
3.
The effect of focusing geometry on slope of carrier-envelope (CE) phase ФCE versus propagation distance from the focus in few-cycle laser pulses is investigated. The slope could be adjusted by changing the distance L between the waist of the incident beam and the lens. At the focus, 偏dФCE/O(Z/ZR) = 0 when L = 0, and 偏dФCE/偏d(z/zR) = -2 when L = ∞. The longer the distance L, the steeper the curve of the CE phase at the focus.  相似文献   
4.
用非线性有限元技术模拟了球囊胀开式血管内支架在内表面压力作用下的自由扩张过程.计算了不锈钢支架扩张过程的径向位移、轴向位移和非线性回复量,结果表明支架变形后的径向位移量随载荷压力增大而增加,最大应力值随之升高.本文的模拟方法为血管内支架的优化设计及性能评估提供了科学的依据.  相似文献   
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