title: Coherent beam combining with an ultrafast multicore Yb-doped fiber amplifier.
abstract: Active coherent beam combination using a 7-non-coupled core, polarization maintaining, air-clad, Yb-doped fiber is demonstrated as a monolithic and compact power-scaling concept for ultrafast fiber lasers. A microlens array matched to the multicore fiber and an active phase controller composed of a spatial light modulator applying a stochastic parallel gradient descent algorithm are utilized to perform coherent combining in the tiled aperture geometry. The mitigation of nonlinear effects at a pulse energy of 8.9 µJ and duration of 860 fs is experimentally verified at a repetition rate of 100 kHz. The experimental combining efficiency results in a far field central lobe carrying 49% of the total power, compared to an ideal value of 76%. This efficiency is primarily limited by group delay differences between cores which is identified as the main drawback of the system. Minimizing these group delay issues, e.g. by using short and straight rod-type multicore fibers, should allow a practical power scaling solution for femtosecond fiber systems.
authors.forename: Lourdes Patricia
authors.initials: LP
authors.lastname: Ramirez
authors.forename: Marc
authors.initials: M
authors.lastname: Hanna
authors.forename: Géraud
authors.initials: G
authors.lastname: Bouwmans
authors.forename: Hicham
authors.initials: H
authors.lastname: El Hamzaoui
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bouazaoui
authors.forename: Damien
authors.initials: D
authors.lastname: Labat
authors.forename: Karen
authors.initials: K
authors.lastname: Delplace
authors.forename: Julien
authors.initials: J
authors.lastname: Pouysegur
authors.forename: Florent
authors.initials: F
authors.lastname: Guichard
authors.forename: Philippe
authors.initials: P
authors.lastname: Rigaud
authors.forename: Vincent
authors.initials: V
authors.lastname: Kermène
authors.forename: Agnès
authors.initials: A
authors.lastname: Desfarges-Berthelemot
authors.forename: Alain
authors.initials: A
authors.lastname: Barthélémy
authors.forename: Florian
authors.initials: F
authors.lastname: Prévost
authors.forename: Laurent
authors.initials: L
authors.lastname: Lombard
authors.forename: Yoann
authors.initials: Y
authors.lastname: Zaouter
authors.forename: Frédéric
authors.initials: F
authors.lastname: Druon
authors.forename: Patrick
authors.initials: P
authors.lastname: Georges