Harmonic dichromatic soliton molecules in synchronous mode-locked fiber lasers

Abstract

Dichromatic soliton molecules, consisting of multiple optical solitons with two carrier frequencies, exhibit distinctive stability and intricate interaction dynamics in nonlinear systems. In this study, we experimentally generate harmonic dichromatic soliton molecules (HDSM) in a synchronously mode-locked fiber laser. By appropriately setting the pump power and adjusting the polarization controller to optimize the cavity state, we successfully generate 2nd-, 3rd-, and 4th-order HDSM, achieving a repetition rate of 76.582 MHz. Using the dispersive Fourier transform technique, we unveiled the various real-time spectral scenarios of these HDSMs. Furthermore, we observe the evolution dynamics of unequal spacing HDSM, which can be considered as 2+4 dichromatic soliton molecular complexes. All these findings provide an intriguing perspective in dynamical intra-molecular evolution of ultrafast nonlinear phenomena and further enrich the research of fundamental science.