Surface damage threshold and structuring of dielectrics using femtosecond laser pulses: the role of incubation

We present results on the surface damage threshold of a-SiO2 and YLF after single and multiple laser pulse irradiation at a pulse duration of 100 fs and radiation wavelength of 800 nm. The surface damage threshold drops dramatically after the first laser shots until reaching an almost constant level. The threshold reduction at low shot numbers is attributed to laser induced defect formation. This has important consequences for applications, such as laser machining and the lifetime of optical components. As an example of relevance to applications, we discuss the generation of high quality micro pockets in a-SiO2 and YLF. q1999 Elsevier Science B.V. All rights reserved