Additive mode locking based on a nonlinear loop mirror ring laser

We present an experimental demonstration of additive pulse mode locking based on a nonlinear loop mirror ring laser. The proposed design uses nonlinear phase shifts induced by a loop mirror. The results show that interference between two overlapping pulses from two coupled fibres, containing a nonlinear medium for power-dependent phase modulation, leads to pulse compression, and can provide mode locking with different repetition rates depending on the interplay or combination between the modulated frequency (active mode locking) and the nonlinearity (passive mode locking) generated in the loop mirror.