Laser Matter Interaction and Warm Dense Matter Science

我的研究项目集中在对激光物质相互作用物理的基本理解及其几个应用。我目前的研究重点是热致密物质体系。热致密物质（WDM）是一种由其可比的热能和费米能定义的物质状态，其密度使得离子之间的库仑势能超过了它们的热动能。这是一个介于凝聚态和等离子体相之间的过渡状态。WDM科学是极端条件下材料科学的一个研究领域，它提供了凝聚态物质和等离子体物理之间的联系，具有重要的基础意义。WDM理论还没有很好地发展，它对理论提出了巨大的挑战，因为WDM对凝聚态理论来说太热了，对等离子体理论来说又太密了。对极端条件下材料的研究引起了巨大的科学兴趣，并被美国国家科学院确定为本世纪的优先研究领域。更好地了解WDM的定量细节对于激光材料的加工、承受极端条件和惯性聚变能的材料设计具有重要意义。

My research program focuses in the fundamental understanding of laser matter interaction physics and several of its applications. My current focus is on the Warm Dense Matter regime. Warm Dense Matter (WDM) is a state of matter defined by its comparable thermal and Fermi energy, and a density such that the Coulomb potential energy between ions exceeds their thermal kinetic energy. This is a transition regime lying between the condensed matter and plasma phases. The WDM science, an area in material science under extreme conditions, is of fundamental significance because it provides a linkage between condensed matter and plasma physics. The WDM theories are not well developed and they present great challenge for theorists because WDM is too hot for condensed matter theories and too dense for plasma theories. The study of materials under extreme conditions has generated enormous scientific interest and was identified by the US National Academy of Sciences as a priority research area for this century. A better understanding of the quantitative details of WDM is important for laser materials processing, design of materials for withstanding extreme conditions and Inertial Fusion Energy. We have developed an experimental platform which can create a single state transient WDM lasts for several picosecond. We have studies its properties in details experimentally by probing it with ultrafast probes including THz, optical, xrays, and electrons etc. Our optical probing studies of AC conductivity of warm dense gold led to insights in its electron heat capacity, electron ion structure interaction, and DC conductivity. Our ultrafast electron diffraction measurement led to a better understanding of ultrafast melting of gold and led to the first observation of the transition of heterogeneous melting to homogeneous melting. We have developed a single shot THz probing technique which will measure the DC conductivity of WDM directly. We have also developed a ring resonator technique to study laser induced damage processes in silicon and obtained insights in the incubation processes. We plan to extend the technique to other semiconductor materials. We also plan to study the fundamental physical processes in laser light scattering of complex materials in support of our applied research in solid content analyzer for tailing management and label free physical cytometry for clinical applications. In summary the main goals for the next 5 years of my research program are to further the fundamental understanding of Warm Dense Matter and laser induced damage mechanisms to make impacts in laser fusion, fusion reactor materials design and laser materials processing. We also like to obtain a better fundamental understanding of the physics of laser light scattering of complex materials in support of our research in several applications based on the laser light scattering technique.