Real-time characterization of dissimilar dissipative soliton interactions in a mode-locked thulium fiber laser

Due to soliton energy quantization, most soliton molecules generated in mode-locked fiber lasers are formed by pulses with similar properties. Soliton trapping and collision between two dissimilar dissipative solitons is presented with distinctive energy, duration, chirp, and spectra in a versatile mode-locked Tm fiber laser which can emit different dissipative solitons simultaneously. Depending on the intracavity polarization settings, the group velocity difference between a strong broadband pulse and a weak narrowband pulse can be controlled and new soliton interaction dynamics are captured in real-time with a polarization-resolving dispersive Fourier transform setup. Unique partial spectral interference patterns and double-scale autocorrelation traces confirm the existence of 'heteronuclear' molecules formed by two dissimilar dissipative solitons with high pulse coherence. We believe the findings here represent a new type of soliton molecules in a mode-locked laser and can provide deeper insights into dissipative soliton interaction dynamics.