ARF EXCIMER LASER-INDUCED BUBBLE FORMATION DURING IRRADIATION OF NACLSOLUTIONS

During application of the 193 nm excimer laser to vitreoretinal surger y, very deep cutting of the retina of about 100 mu m/pulse was detecte d at the energy fluence in the range of 0.25-0.35 J/cm(2)/pulse. At th e surface of the ablating tip insoluble bubbles were observed during t he irradiation. In this paper we study production of these bubbles in aqueous solutions of sodium chloride. The yield of gaseous photoproduc ts was measured as a function of NaCl concentration and energy fluence . At concentrations of 100 g/L powerful water vapor bubbles and shock waves were observed. A mechanism of soft tissue cutting by the 193 nm laser in highly absorbing liquid media is suggested that explains the features of vitreoretinal ablation with this system: (1) the high cutt ing depth when the tip touches the tissue and (2) the absence of cutti ng when the tip is not in contact with the tissue. The advantages of t he ArF laser for microsurgery of internal organs are discussed.