CAVITATION AND ACOUSTIC-EMISSION AROUND LASER-HEATED MICROPARTICLES

We studied transient cavitation bubble formation and acoustic emission around individual laser-heated microparticles using subnanosecond tim e-resolved microscopy. Microcavitation babbles were observed as early as 0.5 ns after the particles were heated by a 30 ps laser pulse. The bubbles expanded to a few micrometers in size and collapsed on the tim e scale of 0.1-1 mu sec. We discuss microcavitation as the origin of a nomalously large photoacoustic effects and nonlinear optical responses observed in laser-heated colloidal suspensions, as well as a mechanis m for cellular damage in biologic tissue containing pigment particles. (C) 1995 American Institute of Physics.