Direct regenerative amplification of femtosecond pulses to the multimillijoule level Ueffing, Moritz ; Lange, Robert ; Pleyer, Tobias ; Pervak, Vladimir ; Metzger, Thomas ; Sutter, Dirk ; Major, Zsuzsanna ; Nubbemeyer, Thomas ; Krausz, Ferenc Abstract Publication: Optics Letters Pub Date: August 2016 DOI: 10.1364/OL.41.003840 Bibcode: 2016OptL...41.3840U