The formation of stable single solitons and various bound states based on a graded index multimode fiber (GIMF) is investigated experimentally for the first time. Taking advantage of the principle… Click to show full abstract
The formation of stable single solitons and various bound states based on a graded index multimode fiber (GIMF) is investigated experimentally for the first time. Taking advantage of the principle of nonlinear multimode interference, a 143.5 cm length of GIMF is bent and two polarization controllers are used to achieve stable passive mode-locking. The spectrum of single solitons centers on 1590.5 nm with a spectral bandwidth of 3.2 nm. 976 fs of pulse duration is obtained at the repetition rate of 14.31 MHz. The maximum output power of 14.572 mW with a corresponding single-pulse energy of 1 nJ is achieved. Meanwhile, all kinds of bound states, including soliton pairs, soliton triplets, soliton quartets, and multiple-pulse bound states with different pulse separations are realized. The bound soliton with two pulses obtained has a fixed pulse interval as the incident pump power is increased. Our results suggest that a GIMF might be employed as an effective saturable absorber for ultrafast photonics applications.
               
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