Technical Feature

Ultrafast Dynamics of Laser-Excited Solids

D.A. Reis, K.J. Gaffney, G.H. Gilmer and B. Torralva

Abstract

We discuss recent experimental and theoretical results on ultrafast materials dynamics. Intense, femtosecond lasers can deposit energy in a time that is short compared with relaxation processes and can generate extremely large carrier densities that drive bond softening, nonthermal melting, and ablation. In particular, we present optical experiments on electronic softening of coherent phonons in bismuth and x-ray experiments on ultrafast disordering in indium antimonide that probe the bonding of the lattice under successively higher carrier concentrations. We review a number of molecular dynamics simulations and their assumptions, which address nonthermal melting. Large-scale molecular dynamics simulations elucidate the role of void formation in laser ablation.

Keywords

• laser ablation;
• simulation

David A. Reis is an assistant professor of physics and applied physics at the University of Michigan. He received his BA degree from the University of California at Berkeley in 1993 and his PhD degree from the University of Rochester in 1999, where he made contributions to accelerator physics and nonlinear quantum electrodynamics. Prior to accepting his current position, he was a postdoctoral fellow with the Center for Ultrafast Optical Science at the University of Michigan. He currently studies ultrafast processes in matter using both x-ray and optical probes.

Reis can be reached at the University of Michigan, Department of Physics, 450 Church St., Ann Arbor, MI 48109-1040 USA; tel. 734-763-9649, fax 734-764-5153, and e-mail dreis@umich.edu.

Kelly J. Gaffney has been a member of the Stanford Synchrotron Radiation Laboratory faculty at Stanford University since 2004. He received his PhD degree in chemistry from the University of California at Berkeley in 2001. His research to date has centered on experimental investigations of ultrafast structural dynamics in a variety of materials and environments. During his PhD work with Charles Harris, Gaffney studied electron dynamics at interfaces. As a postdoctoral fellow in Mike Fayer's laboratory at Stanford University, he used ultrafast vibrational spectroscopy to study the dynamics of energy transfer and structural relaxation in hydrogen-bonding fluids. Since accepting his current position at SSRL, he has focused his attention on the development and extension of ultrafast x-ray science to the study of structural and chemical dynamics.

Gaffney can be reached at Stanford University, Stanford Synchrotron Radiation Laboratory, SLAC, Menlo Park, CA 94025 USA; tel. 650-926-2382, fax 650-926-4100, and e-mail kgaffney@slac.stanford.edu.

George H. Gilmer is a staff physicist at Lawrence Livermore National Laboratory. His research includes the development of theories, atomistic computer models, and special-purpose computers to study solidification, thin-film deposition, crystal growth mechanisms, crystal surface structures, and effects of extreme conditions and energetic particles on surface and bulk material.

Gilmer received a BS degree in mathematics and physics from Davidson College and a PhD degree in physics from the University of Virginia. He worked as a postdoctoral research associate at Cornell University, a professor of physics at Washington and Lee University, and a distinguished member of technical staff at Bell Laboratories before taking his current position at LLNL. He is a fellow of the American Physical Society.

Gilmer can be reached by e-mail at gilmer1@llnl.gov.

Ben Torralva is a research staff scientist in the Materials Science and Technology Division, Chemistry and Materials Science Directorate, at Lawrence Livermore National Laboratory. He came to LLNL as a postdoctoral researcher in 2001. He received a BA degree in 1993 and a PhD degree in 2001, both in physics from Texas A&M University. His current research activities center on modeling the interaction of intense laser pulses with materials using a variety of techniques, ranging from first-principles methods to continuum models. Torralva can be reached at Lawrence Livermore National Laboratory, Materials Science and Technology Division, 7000 East Ave., Livermore, CA 94550 USA; tel. 925-423-4839 and e-mail torr@llnl.gov.