Scalable high-fidelity femtosecond pulse temporal cleaning device based on cross-polarized wave generation Aurélien Ricci 1,2,† , Aurélie Jullien 1 , Jean-Philippe Rousseau 1 , Yi Liu 1 , Aurélien Houard 1 , Patricia Ramirez 3 , Dimitris Papadopoulos 4,3 , Alain Pellegrina 4,3 , Patrick Georges 3 , Frédéric Druon 3 , Nicolas Forget 5 , Rodrigo Lopez-Martens 1 1 Laboratoire d’Optique Appliquée, ENSTA-Paristech, Ecole Polytechnique, CNRS, 91761 Palaiseau, France 2 Thales Optronique SA, Laser Solutions Unit, 2 Avenue Gay-Lussac, 78995 Elancourt, France 3 Laboratoire Charles Fabry, Institut d’Optique, CNRS, Univ Paris Sud 2, Avenue Augustin Fres- nel, 91127 Palaiseau Cedex, France 4 Laboratoire d’Utilisation des Lasers Intenses, CNRS, Ecole Polytechnique, CEA, Univ Pierre et Marie Curie, Palaiseau, France 5 Fastlite, Centre scientifique d’Orsay - Bat.503, Plateau du Moulon, 91401 Orsay, France † Correspondence should be addressed to: aurelien.ricci@ensta-paristech.fr Abstract We report a compact and energy-scalable device for generating high-fidelity fem- tosecond laser pulses based on hollow-core waveguide spatial filtering followed by a crystal for cross-polarized wave (XPW) generation. This versatile device is suited for temporal pulse cleaning over a wide range of input energies (from 0.1 to > 10 mJ) and was successfully qualified on various ultrafast laser systems. Full characteriza- tion of the XPW output is presented. In particular, we demonstrate the generation of 1.6 mJ energy pulses starting from 11 mJ input pulse energy. The temporal con- trast of the pulses is enhanced by more than 4 orders of magnitude. In addition, pulse shortening from 40 fs down to 15 fs yields an overall peak-power transmission of up to 50%. This device not only serves as an integrated pulse contrast filter inside an ultrafast laser amplifier but also as a back-end solution for high-fidelity temporal post-compression of amplified pulses. 1