Transition between noise-like pulses and Q-switching in few-mode mode-locked lasers

Spatiotemporal mode-locked lasers have attracted extensive attention of researchers due to the complex nonlinear evolution process. Compared to single-mode mode-locked lasers, intermodal interactions greatly affect the pulses evolution in spatiotemporal mode-locked lasers. Here, we experimentally investigate the transition process between noise-like pulses and Q-switching pulses in few-mode mode-locked laser by rotating the plates, where a transition state is greatly broadened in the time domain. By means of spectral filtering, we verify that the process is the reconstruction of Q-switching between different modes to noise-like pulses. Furthermore, during the evolution of noise-like pulses, soliton collisions are detected using dispersive Fourier transform technology. Our research contributes to revealing the transient evolution process in few-mode mode-locked lasers, and enriches the study of nonlinear process.