Hot electron generation and manipulation on 'structured' surfaces

Abstract

We examine ways of generating hotter electrons by coupling more light into structured surfaces (nanoparticle coated surfaces and sub-lambda gratings). It is known that such surfaces produce enhanced x-ray yields. We study the effect of laser prepulse conditions on the enhancement of hard x-ray emission (20 - 200 keV) from plasmas produced on nanoparticle (NP)-coated optically polished copper surface, under different prepulse conditions and 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. We suggest that high-contrast ultrashort pulses are essential for nanoparticles to function as yield enhancers. We exploit surface plasmon coupling of light into sub-lambda grating to switch 'ON' a hotter component in hard x-ray spectra from plasma. © 2006 American Institute of Physics.