Transient Optical Nonlinearities Engendered by Femtosecond Laser Filamentation in Gases

气体中飞秒激光丝产生的瞬态光学非线性

• 批准号: 1806594
• 负责人: Dmitri Romanov
• 金额: $ 22.56万
• 依托单位: Temple University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2023-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1806594&HistoricalAwards=false
• 关键词: Transient; Optical; Nonlinearities; Engendered; Femtosecond

Atomic and molecular processes initiated and controlled by intense, ultrashort laser pulses are a subject of steadily growing interest in plasma science and related technology. The laser-induced ionization and excitation of individual atoms and molecules beget in turn various nonlinear optical phenomena in the plasma medium. One such phenomenon, laser filamentation, is enabled by self-focusing of the laser beam, which results in a drastic contraction of the laser pulse and generation of an extended filament at a controllable stand-off distance. Partially ionized plasma is left in the wake of the filamenting laser pulse; it can be probed by subsequent laser pulses and is open to various practical applications. This theoretical research addresses a new realm of transient nonlinear optics in evolving filament-wake channels; it explores longer-lasting optical consequences of strong-field ionization occurring in a relatively dense plasma. The research will advance broader understanding of means to control strong-field light-matter interaction on a microscopic scale. It also directly addresses recent developments of filament-based, multiplex methods of remote detection of complex mixtures, which is a challenge with many technological applications. It is related to control of filamentation dynamics with the aim of remote lasing in the atmosphere, and to developing new sources of attosecond and X-ray pulses.This research concerns the interrelated dynamics of ions, energetic free electrons, and excited neutrals in wake channels of femtosecond laser filaments, as well as the interaction of the evolving system with probe laser pulses. The expected outcomes will form a basis for effective control of filament-wake nonlinear optical effects. The task will be addressed using a combination of ab initio calculations for nonlinear response of individual ions, kinetic modeling of inhomogeneous ionized-gas medium evolution, and density matrix calculations for probe laser coupling with the medium. The objectives include:1) developing predictive models of the evolution of ion density profiles and molecular/atomic excitation in filament wake channels and ionization gratings, which is driven by competing processes of impact ionization, impact electronic excitation of neutrals and ions, dissociative recombination, vibrational excitation, and elastic scattering; 2) calculating dynamic polarizability and hyperpolarizability coefficients of ions in the wake of the ionizing laser pulse (when perturbative approaches become applicable) by implementing the auxiliary-field approach and ab initio calculations, and applying the results to obtain evolving spatial profiles of dynamic quadratic and quartic nonlinear refractive indices in filament wake channels; and3) predicting outcomes of nonlinear interactions of probe laser pulses with the wake channels, including two-beam coupling mediated by ionization gratings, ionic rotational revivals, and controllable spatial-spectral patterns of dynamic Rabi sideband emission. The expected results will be applied to experiments on ionization-related polarization rotation, rotational-revival spectroscopy, and dynamic Rabi sidebands in filament wake channels at the Center for Advanced Photonics Research (CAPR) at Temple University. Further, the ionization-specific nonlinear effects are related to recent experiments on bright higher harmonic generation (up to X-rays) in highly ionized gases and on igniter-heater processes in filament wake channels.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

由强烈的超短激光脉冲引发和控制的原子和分子过程是对等离子体科学和相关技术的持续兴趣的主题。激光诱导的电离和单个原子和分子的激发反过来又在等离子体培养基中各种非线性光学现象。这种现象是通过激光束自聚焦来实现激光丝的一种现象，这会导致激光脉冲的剧烈收缩和在可控制的隔离距离下产生延长的细丝。在丝脉冲脉冲之后，将部分离子化的血浆留下；可以通过随后的激光脉冲来探测它，并且可以使用各种实际应用。这项理论研究介绍了在不断发展的丝状操作通道中的瞬时非线性光学元素的新领域。它探索了在相对密集的血浆中发生的强场电离的持久光学后果。这项研究将提高人们对微观量表控制强场相互作用的方法的更广泛的理解。它还直接解决了基于细丝的复杂混合物远程检测方法的最新发展，这是许多技术应用的挑战。它与控制丝化动力学有关，目的是在大气中进行远程激光，并开发新的Attosond和X射线脉冲来源。这项研究涉及离子的相互关联动力学，能量无能电子的动态，激发的中性和激发的中性，并在feftsoctectement Laser-Laser Lasent the Intersaction coperact usect usect of Ectect of Ectect of covorvals use insaction中。预期的结果将构成有效控制丝 - 效果非线性光学效应的基础。该任务将使用从头算计算的组合来解决单个离子的非线性响应，不均匀离子化气体介质进化的动力学建模以及与培养基探针激光偶联的密度矩阵计算。目的包括：1）开发细丝唤醒通道和电离光栅中离子密度曲线和分子激发的进化的预测模型，这是由影响电离的竞争过程，中性和离子激发的竞争过程所驱动的2）通过实施电离激光脉冲（当扰动方法变得适用时）来计算离子激光脉冲（适用于适用的激光脉冲）的动态极化能力和超极化能力系数，并实施辅助场方法和从头启动计算，并应用结果以获得动态的四边形和惯性浪潮的空间特征，以实现动态和惯性的非上线型辅助式。和3）预测探针激光脉冲与尾通道的非线性相互作用的结果，包括由电离光栅介导的两光束耦合，离子旋转复兴和可控制的动态兔子侧带发射的可控空间光谱模式。预期的结果将应用于在坦普尔大学（Temple University）的高级光子学研究中心（CAPR）中，对与电离相关的极化旋转，旋转复活光谱和动态兔侧带的实验。此外，电离特异性的非线性效应与高度离子化气体中明亮的更高谐波生成（最高X射线）的最新实验以及在细丝唤醒通道中的点火仪过程中进行的。该奖项反映了NSF的法定任务，并通过该基金会的知识分子优点和广泛的影响来评估NSF的法定任务。

项目成果

Intrapulse impact processes in dense-gas femtosecond laser filamentation

浓密气体飞秒激光成丝中的脉冲内冲击过程

• DOI: 10.1103/physreva.97.063411
• 发表时间: 2018
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Romanov, Dmitri A.;Gao, Xiaohui;Gaeta, Alexander L.;Levis, Robert J.
• 通讯作者: Levis, Robert J.

Control of the excited-to-ionized atoms ratio in a dense gas in the wake of an intense femtosecond laser pulse

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
• 发表时间: 2022
• 期刊: Physical Review E
• 影响因子: 2.4
• 作者: Bajpai, Suyash;Romanov, Dmitri A.
• 通讯作者: Romanov, Dmitri A.

Strong-field molecular alignment mediated by nonadiabatic charge localization

• DOI: 10.1103/physreva.100.063423
• 发表时间: 2019-11
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: D. Romanov;R. Levis

Excitation gratings in cross-beam filament wake channels in a dense argon gas: Formation, control, and Rabi sideband manifestation

稠密氩气中交叉束灯丝尾流通道中的激发光栅：形成、控制和拉比边带表现

• DOI: 10.1103/physreve.107.065202
• 发表时间: 2023
• 期刊: Physical Review E
• 影响因子: 2.4
• 作者: Bajpai, Suyash;Romanov, Dmitri A.
• 通讯作者: Romanov, Dmitri A.

Delayed ionization and excitation dynamics in a filament wake channel in a dense-gas medium

稠密气体介质中灯丝尾流通道的延迟电离和激发动力学

• DOI: 10.1103/physreva.102.013110
• 发表时间: 2020
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Romanov, Dmitri A.;Levis, Robert J.
• 通讯作者: Levis, Robert J.