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.
Origin : Files produced by the author(s)
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