Control of ultra-intense single attosecond pulse generation in laser-driven overdense plasmas.
Control of ultra-intense single attosecond pulse generation in laser-driven overdense plasmas.
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DOI：
10.1364/oe.21.031925
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发表时间：
2013-12
期刊：
影响因子：
3.8
通讯作者：
Qingcao Liu;Yan-Xia Xu;X. Qi;Xiaoying Zhao;L. Ji;T. Yu;Luo Wei;Lei Yang;Bi-tao Hu
中科院分区：
文献类型：
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作者：
Qingcao Liu;Yan-Xia Xu;X. Qi;Xiaoying Zhao;L. Ji;T. Yu;Luo Wei;Lei Yang;Bi-tao Hu
圆偏振激光与稠密等离子体相互作用可以获得超强单阿秒脉冲。由于激光诱导等离子体边界的一次性剧烈振荡，在反射的激光脉冲中自然产生高次谐波。利用二维平面粒子模拟和解析模型，我们发现多维效应对AP的产生有很大的影响。在压缩等离子体边界前会发生自聚焦和散焦现象，导致产生的AP在远场发生色散。我们建议通过采用密度调制箔靶（DMFT）来控制反射的高次谐波。当靶密度分布符合激光强度分布时，从等离子体的中心部分产生的阿秒脉冲的强度在横向上的中心范围内具有平坦的分布。实验结果表明，该激光器可以自然产生强度为1.4 × 10（21）W cm（-2）的300阿秒（1as = 10（-18）s）脉冲。进一步的模拟表明，反射的高次谐波特性与调制密度分布和激光场与载波包络之间的相位偏移密切相关。通过将DMFT与合适的驱动激光器相结合，可以在等离子体表面前方的很宽范围内控制从等离子体边界产生的AP的发射方向。
Ultra-intense single attosecond pulse (AP) can be obtained from circularly polarized (CP) laser interacting with overdense plasma. High harmonics are naturally generated in the reflected laser pulses due to the laser-induced one-time drastic oscillation of the plasma boundary. Using two-dimensional (2D) planar particle-in-cell (PIC) simulations and analytical model, we show that multi-dimensional effects have great influence on the generation of AP. Self-focusing and defocusing phenomena occur in front of the compressed plasma boundary, which lead to the dispersion of the generated AP in the far field. We propose to control the reflected high harmonics by employing a density-modulated foil target (DMFT). When the target density distribution fits the laser intensity profile, the intensity of the attosecond pulse generated from the center part of the plasma has a flatten profile within the center range in the transverse direction. It is shown that a single 300 attosecond (1 as = 10(-18)s) pulse with the intensity of 1.4 × 10(21) W cm(-2) can be naturally generated. Further simulations reveal that the reflected high harmonics properties are highly related to the modulated density distribution and the phase offset between laser field and the carrier envelope. The emission direction of the AP generated from the plasma boundary can be controlled in a very wide range in front of the plasma surface by combining the DMFT and a suitable driving laser.