Generation of broad XUV continuous high harmonic spectra and isolated   attosecond pulses with intense mid-infrared lasers
  We present experimental results showing the appearance of a near-continuum in the high-order harmonic generation (HHG) spectra of atomic and molecular species as the driving laser intensity of an infrared pulse increases. Detailed macroscopic simulations reveal that these near-continuum spectra are capable of producing IAPs in the far field if a proper spatial filter is applied. Further, our simulations show that the near-continuum spectra and the IAPs are a product of strong temporal and spatial reshaping (blue shift and defocusing) of the driving field. This offers a possibility of producing IAPs with a broad range of photon energy, including plateau harmonics, by mid-IR laser pulses even without carrier-envelope phase stabilization. 
C. Trallero-Herrero, C. Jin, B. E. Schmidt, A. D. Shiner, J-C.   Kieffer, P. B. Corkum, D. M. Villeneuve, C. D. Lin, F. L\'e...
physics.atom-ph physics.optics