Generation of harmonic mode-locking of bound solitons in the ultrafast fiber laser with Sb2Te3 saturable absorber on microfiber

We report on the observation of the harmonic mode-locking of bound solitons in an erbium-doped fiber laser with an Sb2Te3 topological insulator saturable absorber (SA) on a microfiber. In the regime, there are two solitons in the bound-state pulses and the soliton separation is almost constant at different pump powers. When changing the pump power from 108 mW to 520 mW, the repetition rate of the bound-soliton mode-locking increases from 8th harmonic (105.6 MHz) to 46th harmonic (607.2 MHz). Our experiment results show that the Sb2Te3 topological insulator SA on microfiber could be not only used as an excellent mode locker, but could also provide a highly nonlinear effect for effectively exploring the multiple pulses in the fiber lasers.