Hard x-ray emission in the energy range of 30–300 keV from copper plasmas produced by 100-fs, 806-nm laser pulses at intensities in the range of ${10}^{15}-{10}^{16}\hspace{0.5em}{\mathrm{W}\mathrm{}\mathrm{cm}}^{-2}$ is investigated. We demonstrate that surface roughness of the targets overrides the role of polarization state in the coupling of light to the plasma. We further show that surface roughness has a significant role in enhancing the x-ray emission in the above mentioned energy range.

• Received 22 February 2001

DOI:https://doi.org/10.1103/PhysRevA.65.052903