Imposing temporal and frequency characteristics in a system of coherently combined high peak power photonic crystal fiber lasers

Two main factors that limit the output power from a single fiber laser are damage threshold and the threshold for nonlinear effects. In order to increase the output power it is possible to either increase the effective single mode area of the fiber [1], or to combine several fiber laser sources [2,3]. Currently the largest single mode fibers are commercially available rod-type photonic crystal fiber (PCF) with core diameters up to 100 μm. Nevertheless, also with these PCFs the power is limited by the self-focusing limit in Silica. In the past decade it has been significant interest in passive coherent combining of both solid-state lasers and fiber lasers [3]. However, it was not done with high average and peak power PCF lasers, and specifically not with narrowband lasers.