Intense Picosecond X-Ray Pulses from Laser Plasmas by Use of Nanostructured “Velvet” Targets

We describe the optical, radiative, and laser-plasma physics of a new type of nanostructured surface especially promising as a very high absorption target for high-peak-power subpicosecond laser-matter interaction. This oriented-nanowire material, irradiated by 1 ps pulses at intensities up to ${10}^{17}\mathrm{W}{\mathrm{cm}}^{-2\mathrm{}}$, produces picosecond soft x-ray pulses $50\times$ more efficiently than do solid targets. We compare this to “smoke” or metallic clusters, and solid nanogroove-grating surfaces; the “metal-velvet” targets combine the high yield of smoke targets with the brief emission of grating surfaces.