Laser-generated cavitation in absorbing liquid induced by acoustic diffraction.

Conversion of energy from a heat pulse to acoustic stress is theoretically and experimentally studied in detail. The heat pulse was generated by laser radiation delivered via an optical fiber into an absorbing liquid. The experimental results indicate that tensile stress and cavitation are induced in front of the fiber tip at a distance far below the optical penetration depth of the laser radiation. The occurrence of tensile stress in the acoustic near field of a submerged fiber is explained by acoustic diffraction of the thermoelastic expansion wave. Good agreement between experimental results and theoretical calculations based on a three-dimensional model was found.