High efficiency and broadly wavelength-tunable mid-infrared nanosecond erbium-doped fiber laser pumped at ~1.7 μm

We demonstrate a high efficiency and broadly wavelength-tunable nanosecond mid-infrared (mid-IR) erbium (Er³⁺)-doped fluoride fiber laser pumped at ∼1.7 μm experimentally. In the continuous-wave operation regime, the mid-IR fiber laser output with a slope efficiency of approximately 40% has been obtained with a tuning range 143 nm spanning from 2695 nm to 2838 nm and a linewidth of 0.2 nm. While in the actively Q-switched mode, the mid-IR fiber laser modulated by the acousto-optic modulator (AOM) can deliver stable pulsed laser with a tunable range 133 nm from 2698 nm to 2831 nm, featuring a pulse width of 121 ns, a high signal-to-noise ratio of 50 dB, and an efficiency of 37% at a modulation frequency of 30 kHz. The experimental results highlight the superior efficiency of the pumping scheme and may provide an efficient and precise solution for practical applications.