Observation of soliton bound states in a graphene mode locked erbium-doped fiber laser

We report on the experimental observation of bound states of solitons in a graphene mode locked erbium-doped fiber laser. By using graphene as a saturable absorber, we have obtained stable, single and bound soliton pulses, the latter with a full width at half maximum (FWHM) of 1.49 ps and a fixed pulse separation of 2.46 ps. Our results once again show that bound soliton pulses is an intrinsic feature of fiber lasers independent of the exact mode locking mechanism.