Extreme ultra-violet laser ablation of solid targets

A capillary laser with output in the extreme ultra-violet at wavelength 46.9 nm is used to ablate solid targets of parylene-N (CH), PMMA, aluminum and gold. We summarize results obtained using different focusing optics: a Fresnel zone plate, an off-axis spherical multi-layer mirror and on-axis multi-layer and gold mirrors. The Fresnel zone plate has a small aperture and focuses a small fraction of the laser energy to a small diameter (< 1 µm) with peak intensities 6 x 10^9Wcm^-2. The off-axis spherical multi-layer mirror allows for a measurement of the transmission of the laser through thin targets, but the off-axis geometry produced an aberrated focus. The on-axis multi-layer mirror allows focusing to intensities of approximately 5 x 10^10 Wcm^-2 with a cylindrically symmetric focus.