Study of the interplay of vaporisation, melt displacement and melt ejection mechanisms under single and multiple pulse irradiation

We have used a combination of profilometry, high speed imaging and recoil measurements using a ballistic pendulum to calculate the amount of material removed due to mechanisms of vaporisation, melt displacement and melt ejection when ablating aluminium with a visible nanosecond laser. Single laser pulses are shown to induce material removal predominantly by the mechanism of melt displacement at fluences 7 J.cm-2. Studies of the effects of multiple laser pulses on target demonstrate the additional influence of cumulative heating and the geometric constraints of the ablation crater on material removal. The implications of this study on high resolution laser micromachining will be discussed.6 page(s