Collaborative Research: Exploring Plasma Dynamics of Femtosecond Laser-Induced Photoionization from Near to Mid-Infrared

激光源开发的最新进展使得能够产生以前无法实现的高强度、超短脉冲持续时间和长波长的激光脉冲。 这些新型激光器具有研究地球大气层以及远距离定向能量传输的潜力。实现这些独特应用的核心过程是激光诱导等离子体的产生，称为光电离。目前，在这些极端激光参数下光电离的基本物理特性在很大程度上尚不清楚。 该项目将增进对这些新型激光器产生的光电离和等离子体的基本特性的理解。该项目的教育计划旨在促进等离子体科学以及科学、技术、工程和数学领域的其他职业。该研究将通过在等离子体科学和实验方法主题的几门研究生课程中包含结果和演示来整合到课程中。 K-12 级别的外展和教育将通过开发冷等离子体演示设施和 YouTube 上的一系列等离子体科学教育视频来完成。该项目研究近红外和中红外范围内的强飞秒激光脉冲产生的等离子体的动力学。它将利用微波的弹性散射在新的、未探索的状态下对等离子体中的电子数密度进行绝对定量测量。该项目的具体研究目标包括对前所未有的强激光脉冲波长范围（从近紫外到中红外光谱范围）以及各种强度、气体类型和不同偏振态的电子数密度和光电离率进行彻底的绝对测量。该项目的另一个目标是对飞秒激光气体电离产生等离子体以及随后在大气压力下存在非线性光学现象的各种气体混合物中的等离子体衰变进行联合理论和实验探索。该研究计划将显着加深我们对飞秒激光诱导气体电离和随后的等离子体衰变的了解，目前对此的了解非常有限。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Recent progress in the development of laser sources enables generation of laser pulses at the high intensities, ultra-short pulse durations, and long wavelengths that could not be previously achieved. These novel lasers have potential for studying Earth's atmosphere as well as directed energy transmission over large distances. The central process enabling these unique applications is laser-induced generation of plasmas known as photoionization. Fundamental physical properties of photoionization at these extreme laser parameters are currently largely unknown. This project will advance the understanding of basic properties of photoionization and plasmas generated by these new types of lasers. The educational plan for this project aims to promote plasma science and other careers in science, technology, engineering, and mathematics. The research will be integrated into curricula by including results and demonstrations in several graduate-level courses on topics in plasma science and experimental methods. Outreach and education at the K-12 level will be accomplished by developing a cold plasma demonstration facility and a series of plasma science educational videos on YouTube. This project studies dynamics of plasmas generated by intense femtosecond laser pulses in the near and mid-infrared range. It will utilize elastic scattering of microwaves for absolute quantitative measurements of electron number density in a plasma in new, unexplored regimes. Specific research goals of the project include conducting thorough absolute measurements of electron number density and photoionization rates for an unprecedented wavelength range of intense laser pulses, from the near-ultraviolet to mid-infrared spectral range, and a broad range of intensities, gas types, and different polarization states. Another goal of the project is to conduct joint theoretical and experimental exploration of plasma generation by femtosecond laser gas ionization and subsequent plasma decay in various gaseous mixtures at atmospheric pressure in the presence of non-linear optical phenomena. The research program will significantly deepen our knowledge of femtosecond laser-induced gas ionization and subsequent plasma decay, the understanding of which is currently very limited.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.