Spatial beam cleaning in Ytterbium spatiotemporal mode-locked fiber laser

Spatiotemporal mode-locked (STML) lasers based on multimode fibers enable the simultaneous locking of longitudinal and transverse laser modes [1]. These light sources permit scaling up the generated pulse energy and exhibit complex spatiotemporal dynamics [4]. Here, we introduce and experimentally demonstrate a new laser scheme, leading to high-beam quality output from an STML Yb fiber laser. Our cavity setup is free of isolators, spatial/spectral filters, and dispersion-compensating elements. STML is based on the combined action of nonlinear polarization rotation (NPR) and spatial beam self-cleaning, which acts as Kerr-lens mode locking in bulk lasers. We generated ultrashort high-energy pulses with a near-Gaussian beam profile.