Laser Matter Interaction and Warm Dense Matter Science

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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.