Control of the excited-to-ionized atoms ratio in a dense gas in the wake of an intense femtosecond laser pulse
Control of the excited-to-ionized atoms ratio in a dense gas in the wake of an intense femtosecond laser pulse
复制标题
在强飞秒激光脉冲后控制稠密气体中激发原子与电离原子的比率
DOI：
10.1103/physreve.105.045210
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发表时间：
2022
影响因子：
2.4
通讯作者：
Romanov, Dmitri A.
中科院分区：
文献类型：
--
作者：
Bajpai, Suyash;Romanov, Dmitri A.
我们证明了在致密气体中的灯丝尾流通道中的等离子体成分对驱动飞秒激光脉冲的时间形状的敏感性。在脉冲过程中，强场电离释放出的电子在振荡激光场的驱动下，与邻近的中性原子发生碰撞过程，包括逆韧致辐射、碰撞电离和碰撞激发。到脉冲结束时，这些碰撞过程产生了相当数量的额外的自由电子（或电离原子）和激发原子，这些内容的灯丝尾流通道决定其随后的演变动力学。解决的情况下，高压氩气，并使用这些竞争碰撞过程的动力学模型，我们探索的灵敏度所产生的激发电离原子数密度比的驱动激光脉冲的包络形状。通过考虑几个家庭的脉冲，我们表明，不对称的脉冲包络偏向较早的时间允许有效地控制激发原子电离原子的比例。在激光脉冲的直接尾流中的等离子体成分的脉冲形状控制投射到尾流通道演化和相关的瞬态电子和光学非线性的控制中。
We demonstrate the sensitivity of the plasma composition in the filament wake channel in a dense gas to the temporal shape of the driving femtosecond laser pulse. During the pulse, the electrons released via strong-field ionization and driven by oscillating laser field are actively engaged in collisional processes with neutral neighbor atoms, including inverse Bremsstrahlung, impact ionization, and collisional excitation. By the end of the pulse, these collisional processes produce considerable numbers of additional free electrons (or ionized atoms) and excited atoms, and these contents of the filament wake channel determine its subsequent evolution dynamics. Addressing the case of high-pressure argon gas and using a kinetic model of these competing collisional processes, we explore the sensitivity of the resulting excited-to-ionized atoms number density ratio to the envelope shape of the driving laser pulse. By considering several families of pulses, we show that asymmetric pulse envelopes skewed toward the earlier time allow for efficient control of the ratio of excited atoms to ionized atoms. The pulse-shape control of the plasma composition in the immediate wake of the laser pulse projects into control of the wake channel evolution and of the associated transient electronic and optical nonlinearities.