Time-resolved single-shot revealing pulse evolution dynamics in ultrafast lasers

Abstract Mode-locked lasers are the ideal source for precise measurements, from frequency combs to precise timing, which relies on the accurate control of the intracavity parameters in the lasers to stabilize the pulse. However, by the lack of accurate measurements, the interplays between intracavity parameters and the mode-locked pulse is still not real-time observable. Here, using the dispersive temporal interferometer, we report a method to single-shot probe the pulse evolution dynamics in time domain in the mode-locked laser. As a typical example, we demonstrate the first single-shot observation on the roundtrip time and phase evolutions of intracavity pulse during its buildup and relaxation. Three distinct evolution regimes for pulse buildup are unveiled for the first time. Moreover, the physical mechanism of the time-location and phase changes in these three regimes has also been analyzed, respectively. Our researches present a novel method to observe the intracavity-parameters-to-pulse interaction, which will improve laser design, ultrafast diagnostics, and nonlinear optics.