Ultrafast laser soliton mode-locked at 1.5 μm region based on Cr₂AlC MAX phase as a saturable absorber

In this experiment, a passively mode-locked erbium-doped fiber laser was successfully realized by utilizing chromium aluminum carbide (Cr2AlC) MAX phase as a saturable absorber (SA). The Cr2AlC MAX phase was fabricated by casting method with polyvinyl alcohol to compose a thin film. By a 203-m cavity length, a stable mode-locked laser operating at 1559 nm was achieved at the threshold pump power of 121.69 mW with a pulse width of 4.45 ps and pulse rate of 1 MHz. The pulse energy was 0.91 nJ and output power was 0.91 mW at a maximum pump power of 167 mW. As the cavity length was shortened to 103 m, we observed that pulse width, pulse energy, and output power decreased to 2.5 ps, 1.60 nJ, and 3.02 mW, respectively, while the repetition rate increased to 1.88 MHz at a maximum pump power of 167 mW. To the best of our knowledge, this is the first time utilizing Cr2AlC MAX phase SA to produce the pulse laser in the 1.5-μm region.