Observations of bound states of two and three dissipative solitons in a figure-eight laser in a normal dispersion regime

Dissipative bound-state solitons exhibiting a trapezoid spectral profile and a regular modulation pattern are observed experimentally in a figure-eight fiber laser with large normal cavity dispersion for the first time, to the best of the author's knowledge. The soliton pairs have a pulse duration T-0 of about 800 fs and a peak-to-peak separation of about 8T(0). With the appropriate increase of the pumping strength, the proposed laser generates a bound state of three solitons with a pulse duration T-0 of about 460 fs and a separation between adjacent pulses of about 15T(0). Experimental results show that the bound-state solitons are strongly stable and suggest that they are formed by direct soliton interaction.