Generation of shock waves by hot electron explosions driven by a CO2 laser

We observe shock waves with velocity 2.5×106 cm/sec generated by the interaction of a nanosecond CO2 laser at an intensity of 3×1014 W/cm2 with 12–40-μm-thick aluminum foils. It is proposed that these shock waves are not generated by thermal ablation but rather by hot electron heating and explosion of a layer of Al several microns thick adjacent to the target surface. Shock pressures produced by this process are comparable to the highest pressures yet observed by conventional laser driven thermal ablation.