Real-time observation of the Casimir-like interaction induced pulse dynamics in a fiber laser

We study soliton rain (SR) dynamics experimentally in a passively mode-locked fiber laser based on gold nanoparticles. The complex behavior of the SR, including cases where the speed of the deuterogenic solitons drift was faster than that of the condensed soliton phase (CSP), cases where the drift was slower, and even cases with deuterogenic solitons both faster and slower, have all been observed by adjusting only the cavity polarization controllers and the pump power. It is unveiled that the noise-mediated Casimir-like pulse interaction mechanism accounts for these dynamical patterns. Further, the real-time characteristics of the CSP were observed in detail utilizing the dispersion Fourier transform technique. The study showed that the intensity of the CSP spectrum was redistributed with the soliton drift, while the energy of the CSP spectrum was conserved. This study will provide a new perspective for the regimes of complex pulse dynamic behavior.