Fig. 1. Conceptual outline of the multimode fiber cavity and schematic of spatiotemporal mode-locking with beam self-cleaning. (a) Conceptual outline of dispersion-managed cavity design with indicated temporal dynamics. Laser pumping scheme is not presented. (b) Schematic of mode-locking mechanism and experimentally measured output beam profile evolution. CW, continuous wave; ML, mode-locked.

Fig. 2. Pulse evolution in the laser simulations. Pulse duration and spectral bandwidth variation over the cavity. SA, saturable absorber; PC, pulse compressor.

Fig. 3. Numerical investigation of Kerr-induced beam self-cleaning inside GRIN MMF. Propagation of 450 fs pulse with (a) 40 nJ pulse energy and [20%, 30%, 20%, 20%, and 10%] initial coupling condition; (b) 30 nJ pulse energy and [30%, 20%, 20%, 20%, and 10%] initial coupling condition; (c) 20 nJ pulse energy and [30%, 20%, 5%, 25%, and 20%] initial coupling condition; and (d) 20 nJ pulse energy and [35%, 30%, 20%, 10%, and 5%] initial coupling condition.

Fig. 4. (a) Schematic of the laser cavity and beam profile measurements. QWP, quarter-wave plate; HWP, half-wave plate; PBS, polarizing beam splitter; ISO, isolator; and SF, spatial filter. (b) Evolution of near-field output beam profile for decreasing cavity loss from continuous wave to mode-locked operation for 8-nJ output pulse energy.

Fig. 5. Experimental measurements: (a) measured mode-locked spectrum; (b) intensity autocorrelation trace of the chirped pulse; (c) intensity autocorrelation trace of the dechirped pulse, PICASO-reconstructed autocorrelation intensity (dashed), and PICASO-retrieved dechirped pulse shape (inset); and (d) measured beam profile for mode-locked operation and M2 measurement of the beam profile.