High-order harmonics generated with long wavelength driving fields from an OPA

Summary from only given. High harmonic generation (HHG) is a non-perturbative process that occurs only when the incident excitation field is comparable to the Coulomb field within an atom. Therefore production of XUV/x-rays by HHG in noble gases requires laser intensities above 10/sup 13/ W/cm/sup 2/. We present the generation of HHG with long wavelength driving fields (1.1 to 1.6 /spl mu/m) from a high intensity optical parametric amplifier (OPA).