Laser micromachining of barium aluminium borosilicate glass with pulse durations between 20 fs and 3 ps

Laser-micromachining of high-tech glass has been extended down to a pulse duration of 20 fs generated by a Ti sapphire laser system at a wavelength of 780 nm. A systematic electronmicroscopic study shows that, below 100 fs, an extreme precision and a substantial decrease of the ablation threshold fluence with respect to pulse laser processing with pulses in the picosecond and nanosecond ranee could be achieved. The technical relevance of this novel microtechnology is discussed. The morphology of the ablated areas is not determined by thermal processes. i.e. the heat affected zone. It is controlled by non-linear optical coupling effects. Multi-photon absorption becomes highly efficient below laser pulse durations of 100 fs so that light penetration is minimized and ablation cavities become smooth. At longer pulse durations, a higher light penetration due to a lower number of non-linearly absorbed photons allows mechanical relaxation processes in the glass material leading to roughening. (C) 1998 Elsevier Science B.V.