The Pulse Intensity-Duration Conjecture: Evidence from Free-Electron   Lasers
  The recent remark by G. Mourou and T. Tajima (Science 331, 41 (2011)) on the intensity of the driver laser pulse and the duration of the created pulse that higher driver beam intensities are needed to reach shorter pulses of radiation remains a conjecture without clear theoretical reasoning so far. Here we offer its extension to the case of relativistic electron bunches as the laser's radiating medium (free-electron laser). This also bolsters the understanding of the underlying physical principle of the Conjecture. 
T. Seggebrock, I. Dornmair, T. Tajima, G. Mourou and F. Gr\"uner
physics.acc-ph physics.optics