“…The bound states of solitons were first experimentally observed in a fiber laser mode locked with the nonlinear polarization rotation technique. 374,385 Later, with the development of novel material based real saturable absorber (SA) mode locking techniques, such as the carbon nanotube mode locking and 2D-nano-materials mode locking, formation of bound states of solitons has also been observed in fiber lasers mode locked with the carbon nanotubes, 410,421,423,464,465 graphene, 70,72,74,75,78,80,86,96,100 MoS 2 , 130,131,134 black phosphorus, 109,110 and so on. As these saturable absorbers may be polarization independent, bound states of vector solitons were also reported in fiber lasers.…”