Role of prepulses in the interaction of intense, ultrashort lasers with "structured" surfaces

Abstract

We examine enhanced hard x-ray emission (20 - 200 keV) from plasmas produced on nanoparticles coated optically polished copper surface under different prepulse conditions. We observe that enhancement reduces with increasing prepulse intensity. The dynamics of the process is seen to be in the ps regime. We attribute this to preplasma formation on nanoparticles and subsequent modification/destruction of the nanostructure layer before the arrival of the main pulse. It is suggested that high-contrast ultrashort pulses are essential for nanoparticles to function as yield enhancers.