Ultra-fast solitons in a long cavity multi-mode-fiber-based graphene mode-locked fiber laser with high slope efficiency

A few-layer graphene saturable absorber-based multi-mode fiber is used in a long-cavity fiber laser for passive mode-locking pulse generation. The saturable absorber has a large light-graphene interaction area, which increases its tolerance to pulse energy and decreases its saturable absorption threshold. The long-cavity fiber laser proposed has a high slope efficiency of similar to 8.14%, and when the pumped power is increased to similar to 355 mW, the laser can still operate at passive mode-locking regime with a high output power of similar to 27.28 mW. The output pulses have the pulse energy of similar to 3.2 nJ, pulse width of similar to 883.9 fs, repetition rate of 8.5 MHz, and central wavelength of 1563.5 nm. Such a fiber laser has potential applications in optical communication, microsurgery and laser micromachining.