OPTICAL ABLATION BY HIGH-POWER SHORT-PULSE LASERS

Laser-induced damage threshold measurements were performed on homogene ous and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations 7 ranging from 140 fs to 1 ns. Gold coatings we re found, both experimentally and theoretically, to be limited to 0.6 J/cm(2) in the subpicosecond range for 1053-nm pulses. In dielectrics, we find qualitative differences in the morphology of damage and a dep arture from the diffusion-dominated tau(1/2) scaling that indicate tha t damage results from plasma formation and ablation for tau less than or equal to 10 ps and from conventional heating and melting for tau > 50 ps. A theoretical model based on electron production by multiphoton ionization, joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulse-width and the wavelength scaling of experimental results. (C) 1996 Optical Society of America