ABSTRACT
We have demonstrated the existence of multi-bound solitons having more than two mutually binding solitons in an actively FM mode-locked fiber laser. By properly setting the parameters of the cavity, various multi-soliton bound states from dual to sextuple orders have been experimentally generated at the modulation frequency of 1.0 GHz applied to the optical phase modulator in the lasing cavity. In association with experimental results, numerical simulations have been conducted to show that multi-bound solitons with their relative phase difference of π are stable solutions of the FM mode-locked fiber laser under some specific conditions of the cavity. When the cavity parameters deviate from the optimum levels, individual multi-bound solitons with the phases of their lightwave carriers can no longer hold with π difference. Thus they would reach quasi-stable states with a periodic variation of the generated pulse sequence or unstable state with strong fluctuations in amplitude and temporal position.
