No abstract

No abstract

Nonthermal in vitro ablation of bovine neural tissue by using laser-induced optical breakdown generated by ultrashort laser pulses, with durations from 100 fs to 35 ps and pulse energies of up to 165 µJ, has been investigated. The experiments were performed at wavelengths ranging from 630 to 1053 nm by using a femtosecond Ti:Sapphire laser, a femtosecond dye laser, and a picosecond Nd:YLF laser system. Tissue ablations have been achieved by focusing the laser beam on the surface of the tissue, to a spot diameter of 5-20 µm, resulting in the generation of a microplasma. Laser pulses from the Ti:Sapphire laser with 140 fs duration showed a two times higher efficiency of ablation than the longer 30 ps pulses from a Nd:YLF laser with an identical pulse energy. At pulse energies of 140 µJ, single pass excisions deeper than 200 µm were generated by the 140 fs pulses. In addition, the fluence at threshold of the ablation was found to be reduced for shorter pulse durations. For 3 ps laser pulses at 630 nm, we measured the fluence at threshold to be about 5.3 J/cm 2 ; for 100 fs pulses from the same laser the experimental threshold was at 1.5 J/cm 2. Histopathological examinations and scanning electron micrographs confirm the high quality of the excisions. No sign of significant thermal damage was observed.