Efficient Extreme UV Harmonics Generated from Picosecond Laser Pulse Interactions with Solid Targets

The generation of high harmonics created during the interaction of a 2.5 ps, 1053 nm laser pulse with a solid target has been recorded for intensities up to ${10}^{19}\mathrm{W}{\mathrm{cm}}^{\ensuremath{-}2}$. Harmonic orders up to the 68th at 15.5 nm in first order have been observed with indications up to the 75th at 14.0 nm in second-order diffraction. No differences in harmonic emission between $s$ and $p$ polarization of the laser beam were observed. The power of the 38th high harmonic at 27.7 nm is estimated to be 24 MW.