Wavelength-tunable soliton molecule in spatiotemporal mode-locked Yb-doped fiber laser

Abstract

Spatiotemporal mode-locking (STML) fiber lasers could realize the synchronized locked of multiple transverse and longitudinal modes, which could be regarded as an ideal platform to investigate high-dimensional nonlinear dynamics. The observation of STML in the soliton molecule state could offer a unique opportunity to reveal the mechanism of molecular complexity. Due to the distinctive spatiotemporal characteristics, realizing the wavelength tunable of soliton molecule in STML fiber laser is still challenging. In this letter, we report wavelength-tunable soliton molecules in an STML Yb-doped fiber laser. By rotating the wave plates at a fixed pump power, both single dissipative soliton (SDS) and various soliton molecules, including loose bounded dissipative soliton pairs (BDSPs), tight BDSPs, soliton molecules of triplet pulses or soliton molecules of quadruplets pulses, have all realized wavelength tunable with a tuning range of ∼25 nm. The realization of the wavelength tunable and the formation of the soliton molecule can all be attributed to the tunable comb filter and saturable absorber induced by the nonlinear polarization rotation technique. The formation of SDS and BDSPs was further confirmed by the numerical simulations. And the numerical results contribute to further comprehending the nonlinear dynamics of the STML fiber laser.