FEMTOSECOND PULSE VISIBLE LASER PROCESSING OF FIBER-COMPOSITE MATERIALS

A first investigation on the ablation of composite materials like carb on and silicon-carbide reinforced alumo- and borosilicate glasses by 3 00 fs laser pulses (620 nm) in comparison to experiments with 17 ns pu lse excimer laser (308 nm) treatment is presented. In all composites, femtosecond laser scans with a fluence of less than 2 J cm(-2) produce well defined cuts with smooth side walls in contrast to the nanosecon d laser result where extremely incongruent ablation is observed. Visib le lasers should not be applicable because SiC and the glasses are pra ctically transparent. Visible subpicosecond pulses of high intensity i n the TW cm(-2) range allow multi-photon absorption accompanied by inc ubation phenomena. The morphology of the groove edges reveal the contr asting ablation thresholds and rates of the fibre and glass materials. The ablation thresholds of the transparent components, i.e. the glass matrices and SiC, are about one order of magnitude greater than that of carbon which is similar to 0.15 J cm(-2). Incubation effects are im portant for the absorption mechanisms in the transparent materials. Wh en a critical number of pulses has not been reached at the SiC-glass c omposites, only the glass is preferentially ablated, and the fibres re main intact. This is in contrast to the C-glass composites where the a blation behaviour is opposite.