Tunable picosecond pulse generation from 3.05 to 3.65 μm enabled by InAs/GaSb superlattice SESAM

In this Letter, we report mode-locking operation of a red-diode-pumped Er³⁺/Dy³⁺ codoped fluoride fiber laser at >3 μm, for what we believe is the first time, by employing an InAs/GaSb Type-II superlattice semiconductor saturable absorber mirror. At the free-running wavelength of 3447.9 nm, picosecond pulses with a repetition rate of 17.03 MHz and a temporal width of 4.2 ps have been achieved, yielding a maximum energy of 10.2 nJ with a corresponding peak power of 2.3 kW. Attributable to the wideband feature stemming from the combination effect of Er³⁺ (⁴F_9/2→⁴I_9/2) and Dy³⁺ (⁶H_13/2 →⁶H_15/2) transitions, the wavelength of picosecond pulses can be tuned from 3046.9 to 3644.8 nm, where the ∼600 nm span is the widest level of mid-infrared (MIR) mode-locked fluoride fiber lasers, to the best of our knowledge. These results provide the new opportunity for wideband picosecond pulse generation in the MIR.