高晓辉博士学术报告
发布人:幸江涛  发布时间:2017-06-12   浏览次数:10

题目:Lonization dynamics and intense ultrashort pulse propagation in gases

主讲人:高晓辉博士(哥伦比亚大学)

时间:2017613日(周二),11:00-12:00

地点:理工学院光电工程系414会议室

主持人:狄红卫教授

AbstractInteraction of intense ultrashort laser pulses with matter is of fundamental interest and of practical importance. It has opened up applications such as femtosecond filamentation for remote sensing and pulse compression,andhigh-order harmonic generation for imaging and attosecond science. Ionization is a likely outcome of intense laser-matter interactions, and plays a critical role in various phenomena such as balancing self-focusing in femtosecond filamentation, achieving phase-matching in high-order harmonic generation, and optimizing injection in electron accelerators.

In this presentation, I will talk about ionization dynamics in different gas targets. First, I will present the plasma dynamics inside a femtosecond-pulse-induced filament generated in a high-pressure argon gas.We observe ionization immediately following the pulse with up to a 3-fold increase in the electron density within 30 picoseconds after the filamentary propagation of the femtosecond pulse. This post-pulse ionization indicates complex collisional excitation dynamics during the pulse. Second, I will talk about intense pulse propagation from the ultraviolet to the mid-infrared in gas-filled capillaries. For shorter wavelength pulses and smaller capillary diameters, ionization-induced refraction excites higher-order modes, and their constructive interference leads to spatio-temporal localization. Last, I will show how to determine the fraction of atoms in cluster phase in a pulsed supersonic gas jet by measuring femtosecond evolution of the jet’s refractive index following an ionizing pulse by single-shot frequency domain holography.

Biography

XiaohuiGao received his Ph.D. in Physics in 2012 from the University of Texas at Austin. His Ph.D. work was focused on the interaction of ultrafast intense laser pulses with atomic clusters.He joinedthe group of Professor Alexander Gaeta at Cornell University as a Postdoctoral AssociateinJune of 2013, and remained there until the group moved to Columbia University in 2015. He was then a Postdoctoral Research Scientist at Columbia University from 2015 to 2017. His research topics at Columbia University include femtosecond filamentation in new regimes and intense pulse propagation in gas-filled fibers.