Photoacoustic waves excited in liquids by fiber-transmitted laser pulses

The acoustic wave field generated in front of a submerged fiber tip by short laser pulses is theoretically and experimentally studied by fast imaging and optical pressure measurements. It is shown that the finite size of the fiber causes strong tensile stress leading to cavitation. Depending on the absorption coefficient of the laser radiation, cavitation-induced bubble formation occurs inside (low absorption) or outside (high absorption) the volume of heat deposition. The results are used to characterize the cavitation bubble formation mechanisms and to predict possible consequences for applications of fiber-guided short-pulsed laser sources in medicine. (C) 1998 Acoustical Society of America. [S0001-4966(98)02408-4].