Ultrafast laser ablation of metals with a pair of collinear laser pulses

We investigated the process of ultrafast laser ablation of metallic targets induced by a pair of identical laser pulses, with either p or s polarizations, temporally delayed from approximate to 1 ps to a few nanoseconds. We used fast ion probe diagnostics to characterize the ion plume at the moderate laser intensity (approximate to 10(12) W/cm(2)) typically employed in ultrafast laser deposition and material processing. We observed a consistent time-correlated enhancement of the ion yield and velocity, which lends itself to an interesting and useful method for manipulating ablation plasma characteristics. The mechanisms producing this feature are also discussed.