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排序方式: 共有196条查询结果,搜索用时 366 毫秒
61.
不同烧蚀条件下飞秒激光脉冲诱导ZnO纳米结构研究 总被引:6,自引:5,他引:1
烧蚀条件对飞秒激光脉冲诱导氧化锌纳米结构有重要影响.研究了800 nm,150 fs,250 kHz的飞秒激光脉冲分别在空气中,去离子水中以及无水乙醇中垂直聚焦于氧化锌晶体表面,诱导形成不同形态的纳米结构.实验结果表明,在空气中利用飞秒激光脉冲辐照样品表面,形成了周期为180 nm的纳米线;在去离子水中辐照诱导形成了由氧化锌纳米线聚集而成的"纳米球";在无水乙醇中形成出现分叉结构的纳米线.拉曼光谱分析辐照前后晶体晶相结果表明,形成的纳米结构相对于辐照前特征峰437 cm-1强度有所下降,在570 cm-1处的峰值则显著增强.分析了在各种烧蚀条件下诱导形成纳米结构的演化过程以及物理机理. 相似文献
62.
Different conical emission (CE) patterns are obtained experimentally at various incident powers and beam sizes of pump laser pulses with pulse durations of 7fs, 44fs and 100fs. The results show that it is the incident power but not the incident power density that determines a certain CE pattern. In addition, the critical powers for similar CE patterns are nearly the same for the laser pulses with the same spectral bandwidth. Furthermore, as far as a certain CE pattern is concerned, the wider the spectral bandwidth of pump laser pulse is, the higher the critical power is. This will hopefully provide new insights for the generation of CE pattern in optical medium. 相似文献
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We present three possible design options of laser plasma acceleration (LPA) for reaching a 100-GeV level energy by means of a multi-petawatt laser such as the 3.5-kJ, 500-fs PETawatt Aquitane Laser (PETAL) at French Alternative Energies and Atomic Energy Commission (CEA). Based on scaling of laser wakefield acceleration in the quasi-linear regime with the normalized vector potential a0 =1.4(1.6), acceleration to 100 (130) GeV requires a 30-m-long plasma waveguide operated at the plasma density n e ≈ 7×10 15 cm-3 with a channel depth Δn/ne = 20%, while a nonlinear laser wakefield accelerator in the bubble regime with a0≥2 can reach 100 GeV approximately in a36/a0-m-long plasma through self-guiding. The third option is a hybrid concept that employs a ponderomotive channel created by a long leading pulse for guiding a short trailing driving laser pulse. The detail parameters for three options are evaluated, optimizing the operating plasma density at which a given energy gain is obtained over the dephasing length and the matched conditions for propagation of relativistic laser pulses in plasma channels, including the self-guiding. For the production of high-quality beams with 1%-level energy spread and a 1π-mm-mradlevel transverse normalized emittance at 100-MeV energy, a simple scheme based on the ionization-induced injection mechanism may be conceived. We investigate electron beam dynamics and effects of synchrotron radiation due to betatron motion by solving the beam dynamics equations on energy and beam radius numerically. For the bubble regime case with a0=4, radiative energy loss becomes 10% at the maximum energy of 90 GeV. 相似文献
66.
Phase-matched high-order harmonic generation in Ar gas-filled cell is investigated experimentally. We obtain phase-matched 27th order harmonic driven by a commercially available solid-state femtosecond laser system at 0.55 mJ/pulse energy level and 1-kHz repetition rate. Moreover, we find that the spatial distribution of intensity of high-order harmonics is flat-top profile other than a Gaussian one under the condition of optimized conversion efficiency in the static gas cell. 相似文献
67.
周期性极化铌酸锂晶体中半非共线型宽带光学参变放大理论研究 总被引:1,自引:0,他引:1
基于周期性极化铌酸锂晶体(PPLN)的准相位匹配光参变放大过程,通过倾斜周期极化铌酸锂晶体中极化域(极化光栅)一定角度,实现了介于共线匹配方式和非共线匹配方式之间的一种半非共线型准相位匹配方式,并以该匹配方式下的各光矢量几何关系得出相位匹配曲线,找到在特定抽运光和信号光波长下能获得宽带增益放大的周期极化长度。并研究其极化倾斜角度与温度特性。模拟计算表明,在合适的角度与温度条件下,该方式可以532 nm抽运光抽运的信号光在800 nm和1064 nm处均获得宽带光参变放大。 相似文献
68.
We investigated nonlinear optical properties of ZnO-Nb2O5-TeO2 glass excited by a femtosecond laser with time-resolved four-wave mixing (FWM) technique. The unusual FWM signals were observed in samples with ZnO dopant. The mechanism for the optical nonlinearities was discussed. 相似文献
69.
We have performed time-resolved degenerate four-wave mixing(DFWM)experiments in 75Nb2O5-20TeO2-5ZnO glasses doped by Er2O3 at different excitation intensities and lattice temperatures.DFWM signalexhibits three peaks at high excitation intensities,where a main peak appears at zero time delay and tworather weak side peaks locate symmetrically at the negative and positive time delay,respectively.Themain peak is attributed to local-field effect and two side peaks are attributed to Coulomb interaction(CI). 相似文献
70.