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

摘要

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