Coherent beam combining with an ultrafast multicore Yb-doped fiber amplifier

Patricia Ramirez (1) , Marc Hanna (1) , Géraud Bouwmans (2) , Hicham El Hamzaoui (2) , Mohamed Bouazaoui (2) , Damien Labat (2) , Karen Delplace (2) , Julien Pouysegur (1, 3) , Florent Guichard (3, 1) , Philippe Rigaud (4) , Vincent Kermène (4) , Agnès Desfarges-Berthelemot (4) , Alain Barthélémy (4) , Florian Prévost (5) , Laurent Lombard (5) , Yoann Zaouter (3) , Frédéric Druon (1) , Patrick Georges (1)

1 Laboratoire Charles Fabry / Lasers
2 PhLAM - Laboratoire de Physique des Lasers, Atomes et Molécules - UMR 8523
3 Amplitude Systèmes
4 XLIM-PHOTONIQUE - PHOTONIQUE
5 ONERA - The French Aerospace Lab [Châtillon]

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.

Domaines: Optique [physics.optics]

Patricia Ramirez, Marc Hanna, Géraud Bouwmans, Hicham El Hamzaoui, Mohamed Bouazaoui, et al.. Coherent beam combining with an ultrafast multicore Yb-doped fiber amplifier. Optics Express, 2015, 23 (5), pp.5406-5416. ⟨10.1364/OE.23.005406⟩. ⟨hal-01120367⟩