Bound solitons operation of a fiber laser mode-locked by carbon nanotubes

Bound solitons are observed in a fiber laser passively mode-locked by carbon nanotube saturable absorber for the first time. Such bound solitons are observed to be stable, and have the characteristic of discrete, fixed soliton separations and phase difference of π. Our results once again show that the bound soliton emission is an intrinsic feature of the mode-locked soliton fiber lasers.