STUDIES OF LASER-INDUCED CAVITATION AND TISSUE ABLATION IN SALINE USING A FIBER-DELIVERED PULSED HF LASER

We describe studies of the interaction of approximately 400 ns duration, fibre delivered, multiline (2.6-3.0 mum) HF-laser pulses with cornea and retina samples in saline. In this wavelength region water exhibits strong absorption (beam penetration depth - 1.6 mum) and laser heating leads to the creation of a hot, high pressure, vapour cavity (laser-induced cavitation) at the fibre tip. The dynamics of vapour cavity growth have been investigated experimentally using the laser shadowgraph technique and theoretically by employing an equivalent spherical cavity model for an incompressible liquid. Measurements of ablation rates and transient acoustic pressures for cornea ablation in saline, together with scanning electron microscope evaluation of irradiated samples are used to assess the damage range and mechanisms for this mid-IR laser in a strongly absorbing fluid.