Time-resolved studies of plasma-mediated surface ablation of soft biological tissue with near-infrared picosecond laser pulses

Time-resolved video photographs have been taken in order to investigate plasma induced surface ablation of soft tissue by IR picosecond laser pulses with energies of about 1 mJ. The emission and propagation of shock waves in the irradiated tissue as well as in the surrounding air environment was studied. The pressure amplitudes of the shock transients were determined from the measured shock velocities. A decay of the pressure amplitude below 100 MPa was observed within a distance of about 200 micrometers from the center of laser induced optical breakdown. The dynamics of the ablation crater and the ejection of the ablation fragments was studied on a larger time scale. The maximum expansion of the ablation crater was measured to be about 200 (Mu) m at temporal delays of 4-5 microsecond(s) after the impact of the laser pulse. Furthermore, generation and propagation of a surface deformation wave was observed. Thus, we present a detailed and consistent description of all phenomena occurring during plasma-mediated surface ablation of soft tissue.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.