PHYSICAL PROBLEMS OF EXCIMER-LASER CORNEA ABLATION

ArF excimer laser ablation of corneal tissues (in vitro, pig) is investigated. Scanning electron microscopic analysis shows that the spatial resolution of the ablation is better than 1 mum. The etching rate and etched depth is found to be proportional to the logarithm of the laser fluence and the number of shots, respectively. To investigate the dynamic processes a laser-based, ultrafast photographic arrangement was constructed having a temporal resolution of 1 ns. The maximum speed of the shock wave generated during ablation is found to be as high as 4000 m/s. The ejection of the ablation plume with plume-front velocities in the range of 600 m/s is also observed. A new type of surface wave generated by the recoil forces of the ablated material is found. The amplitude of this surface wave can be as high as 0.4 mm.