We report significant enhancements in light coupling to intense-laser-created solid plasmas via surface plasmon and “lightning rod” effects. We demonstrate this in metal nanoparticle-coated solid targets irradiated with 100 fs, 806 nm laser pulses, focused to intensities $\sim {10}^{14}–{10}^{15}\mathrm{W}{\mathrm{c}\mathrm{m}}^{-2}$. Our experiments show a 13-fold enhancement in hard x-ray yield (10–200 keV) emitted by copper nanoparticle plasmas formed at the focal volume. A simple model explains the observed enhancement quantitatively and provides pointers to the design of structured surfaces for maximizing such emissions.

• Received 11 April 2002

DOI:https://doi.org/10.1103/PhysRevLett.90.115002