Synchronous dynamics of passively synchronized Yb-doped fiber lasers

A tightly synchronized fiber laser system composed of two mode-locked Yb-doped fiber lasers in a master-slave configuration is built. The synchronization could sustain for more than 6 h, and the maximum tolerance of cavity length mismatch is measured to be about 210 μm. Afterward, a time-stretch dispersive Fourier transform technique is introduced to analyze the synchronization process over multiple cycles. The pulse evolution, center wavelength shift, spectral reshaping, and broadening are all clearly detected. And the synchronization time is experimentally determined on the order of microseconds (hundreds of roundtrips). These results also show the seed pulse acting as a temporal gate for mode locking in some cases. To the best of our knowledge, this is the first time that pulse formation, spectral evolution, center wavelength shift, and synchronization time during the synchronization process are precisely revealed in experiment. These results would help to improve the performances of synchronized laser devices and deeply understand the mechanisms of the synchronization process and other light-light interactions in materials.