<title>Ultrafast laser-induced microexplosions: explosive dynamics and submicrometer structures</title>

Abstract

Tightly focused femtosecond laser pulses can be nonlinearly absorbed inside transparent materials, creating a highly excited electron-ion plasma. These conditions exist only in a small volume at the laser focus. This tight confinement and extreme conditions lead to an explosive expansion -- a microexplosion. In solid materials, a microexplosion can result in permanent structural changes. We find that the damage produced by femtosecond pulses in this way is surprisingly small, with only a 200-nm diameter. Material left at the center of the microexplosion is either amorphous and less dense or entirely absent. The threshold for breakdown and structural change is nearly independent of material. Time- resolved measurements of microexplosions in water allow us to observe the dynamics of the explosive expansion. The structural changes in solids resulting from microexplosions allow for three-dimensional data storage and internal microstructuring of transparent solids.