Real‐Time Observation of the Formation of Dual‐Wavelength Mode Locking

Abstract

Herein, the first real‐time observation of buildup dynamics for asynchronous dual‐color solitons in a mode‐locked fiber laser is presented. By means of the time‐stretch dispersive Fourier transform technique, experimental observations reveal that asynchronous solitons collision plays important role in spurring new waveband soliton generation, as well as resulting in partial or full soliton annihilation. Dual‐wavelength mode‐locking lasers delivering asynchronous dual‐color solitons are excellent sources for dual‐comb spectroscopies. Up to now, diverse approaches have been developed to implement dual‐wavelength lasers. However, the buildup dynamics of dual‐color solitons have not been well revealed. Here, by means of the time‐stretch dispersive Fourier transform technique, real‐time observation of the buildup process and propagation dynamics of asynchronous dual‐color solitons in a mode‐locked fiber laser are reported. In addition to the typical phases that have been well discussed on buildup dynamics of conventional solitons, such as raised relaxation oscillation and spectral beating behavior, it is observed that optical or solitons collision plays a key role in facilitating the buildup of dual‐ or multi‐wavelength mode locking. Specifically, when the dual‐wavelength solitons carrying the same color photons encounter in the time domain, their collision induces the solitons explosion and brings about the new evolved mode‐locking pulse at another waveband. Experimental results agree well with numerical predictions and bring insights to the understanding of nonlinear dynamics in fiber lasers.