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

近年来，随着激光光源的发展，能够产生高强度、超短脉冲宽度和长波长的激光脉冲，这是以前无法实现的。 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中心过程是激光诱导产生等离子体，称为光电离。在这些极端的激光参数下光电离的基本物理性质目前在很大程度上是未知的。 该项目将推进对这些新型激光器产生的光致电离和等离子体的基本性质的理解。该项目的教育计划旨在促进等离子体科学和其他科学，技术，工程和数学方面的职业。该研究将纳入课程，包括结果和演示，在几个研究生水平的课程等离子体科学和实验方法的主题。将通过开发冷等离子体演示设施和在YouTube上播放一系列等离子体科学教育视频，实现K-12水平的推广和教育。本计画主要研究飞秒强激光脉冲在近红外线及中红外线范围内所产生之电浆动力学。它将利用微波的弹性散射，在新的，未探索的制度，在等离子体中的电子数密度的绝对定量测量。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）的电子数密度和光电离率进行彻底的绝对测量，以及广泛的强度，气体类型和不同的偏振状态。该项目的另一个目标是在大气压下，在存在非线性光学现象的情况下，通过飞秒激光气体电离和随后在各种气体混合物中的等离子体衰减来进行等离子体产生的联合理论和实验探索。该研究计划将大大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，目前对这方面的了解非常有限。该奖项反映了NSF的法定使命，并通过使用基金会的知识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.