Production efficiency of thin metal flyers formed by laser ablation

Abstract

Thin metal plates (flyers) were launched from an aluminum-coated glass support using nanosecond and picosecond Nd: yttrium aluminum garnet laser pulses at 1.06 μm. The velocity of the flyers was measured as a function of incident fluence and of the delay between two consecutive laser pulses using a time-of-flight method. Profilometric scans of the craters formed on the substrate provided an accurate mapping of the crater’s morphology and enabled a realistic estimation of the flyer’s mass. The combination of these measurements allowed the determination of the flyer’s kinetic energy and hence the efficiency of the launching process as a function of the initiating laser’s energy. Threshold fluences of 1.3–2.0J∕cm2 and acceleration efficiencies up to 0.45 were measured under our experimental conditions. The results show that acceleration efficiency rises with the energy of initiating laser and drops when the delay time between two pulses of 10-ns full width at half maximum becomes larger. The acceleration efficiency is also reduced (relative to a 10-ns laser pulse) when the process is initiated by a single 20-ps pulse. On the basis of these data we assume that the launching efficiency may be optimized by using 2-ps laser pulses with a subnanosecond delay time between them.