Investigation of the dynamic process of high fluence femtosecond laser ablation of aluminum by ultrafast time-resolved shadowgraphy

Abstract

The dynamic process of 800 nm high fluence femtosecond laser ablation of aluminum is revealed by ultrafast time-resolved shadowgraphs. Both single and multiple laser pulses at perpendicular or oblique incidence are employed in the experiment. It is demonstrated that femtosecond laser ablation of aluminum with a fluence of 40 J/cm 2 is a complex process involving both photothermal and photomechanical mechanisms. For a single ablation pulse, the propagation direction of the ejected material remains normal to the target surface regardless of the incidence angle of the laser. For the multiple pulses ablation with an oblique incidence angle, the propagation direction of the ejected material deviates from the normal of the target surface gradually as the number of ablation pulses increases due to the topographic change of the ablated region.