Mode-locked seven-core multicore photonic crystal fiber laser with a saturable absorber

Multicore Photonic Crystal Fiber (MC-PCF) have multiple cores close to each other, which allows coherent beam combining (CBC). MC-PCF can scale the output power by increasing the number of cores by CBC if the in-phase mode is selected. We demonstrate simultaneous realization of phase-locked and mode-locked laser by using Yb-doped 7-core MC-PCF by a semiconductor saturable absorber placed in the near-filed inside a resonator. High energy 333 nJ pulses were obtained directly from a mode-locked fiber laser oscillator at a 42.4 MHz repetition rate with an average power of 14.1 W at 24 W excitation. We observed the direct output pulse duration of 52 ps by assuming a sech(2) profile. However, it may be noise-like pulses because of no variation when we performed pulse compression. Single-pulse operation was achieved by increasing the bandwidth of intracavity filter. At this time, 129 nJ, 42.4 MHz pulses were generated with a 5.5 W average power and the direct output pulse duration of 42 ps.