Laser damage on short time scales is an area of active research. Because short pulses produce damage with a smaller statistical uncertainty than long pulses, femtosecond lasers for submicron-precision material removal have become attractive. Applications include micromachining, ophthalmic surgery, electronics and data storage.Researchers have conducted numerous experimental and theoretical studies to determine the mechanisms of laser damage. However, experimental observations and theoretical models are rarely in complete agreement. Now researchers from the University of Michigan's Center for Ultrafast Optical Science in Ann Arbor, Mich., present a theoretical model that they say resolves past discrepancies. It sheds light on the respective roles of multiphoton ionization, tunnel ionization and impact ionization. Details of the group's work appear in the May 10 issue of Physical Review Letters.