Role of surface roughness in hard-x-ray emission from femtosecond-laser-produced copper plasmas

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 1015-1016 W 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