LASER MICROMACHINING OF BARIUM ALUMINUM BOROSILICATE GLASS WITH PULSEDURATIONS BETWEEN 20 FS AND 3 PS

Laser-micromachining of high-tech glass has been extended down to a pu lse duration of 20 fs generated by a Ti sapphire laser system at a wav elength of 780 nm. A systematic electronmicroscopic study shows that, below 100 fs, an extreme precision and a substantial decrease of the a blation threshold fluence with respect to pulse laser processing with pulses in the picosecond and nanosecond ranee could be achieved. The t echnical relevance of this novel microtechnology is discussed. The mor phology of the ablated areas is not determined by thermal processes. i .e. the heat affected zone. It is controlled by non-linear optical cou pling 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 hig her light penetration due to a lower number of non-linearly absorbed p hotons allows mechanical relaxation processes in the glass material le ading to roughening. (C) 1998 Elsevier Science B.V.