Mid-infrared SESAM mode-locked Er:CaF2-SrF2 bulk laser at 2.73 µm

To the best of our knowledge, this is the first time that a mid-infrared Er3+:CaF2-SrF2 laser has achieved continuous-wave mode-locked operation by a semiconductor saturable absorber mirror. The laser emits a maximum output power of 93 mW at 2.73 µm with a repetition rate of approximately 69 MHz and demonstrates a high signal-to-noise ratio of around 71 dB. In addition, a MgF2 birefringent plate was utilized to enable wavelength tuning of the Er3+:CaF2-SrF2 laser, resulting in operation at approximately 2.73 µm, 2.75 µm, 2.79 µm, and 2.81 µm. These results demonstrate that Er3+:CaF2-SrF2 is a promising alternative for the generation of efficient diode-pumped mode-locked lasers around 2.8 µm.