Spatial self-beam cleaning in spatiotemporally mode-locked fiber lasers

In recent years, by exploiting the low modal dispersion of graded-index multimode fibers, spatiotemporal mode-locking was demonstrated in multimode fiber laser cavities [1] . The use of multimode fibers inside the laser cavity is proposed as a new path to achieve high energy and peak power pulses from fiber lasers. However, the introduction of spatial modes to fiber lasers resulted in the generation of low-quality output beam profiles with spatiotemporal mode-locking [2] - [3] . To overcome this limitation, improvement in the output beam profile of a spatiotemporal mode-locked fiber laser was reported but limited with amplifier similariton pulse type [4] .