Single-shot observation of stretched-pulse buildup dynamics in an ultrafast fiber laser

Time-stretch dispersive Fourier transform (TS-DFT) technique offers a powerful way to investigate the non-repetitive formation dynamics of mode locking. Here we have unveiled the entire buildup dynamics of stretched pulse in a passively mode-locked fiber laser using TS-DFT technique. The entire buildup dynamics include relaxation oscillation, transient bound states, beating dynamics, intensity fluctuation and stable stretched pulse finally. These results provide a direct insight into the start-up dynamics of stretched pulse, which could be helpful for the understanding of mode locking formation mechanism.