Sub-60-fs SESAM mode-locked Yb, Y: CaF₂-SrF₂ laser

We conducted a comprehensive study on the optical spectroscopy properties and laser performances of a Yb, Y: CaF₂-SrF₂ co-doping mixed crystal. Our investigation included an analysis of the absorption, emission, and gain cross-sections, and we were able to achieve a wide tuning range of 75.4 nm. Notably, we obtained a maximum average output power of 265 mW with a remarkable 58.3% optical efficiency under 658 mW absorbed pump power in the continuous wave regime. In the mode-locked regime, we achieved a pulse duration of 53 fs and an average output power of 30 mW using a commercial semiconductor saturable absorber mirror (SESAM). The pulse peak power was 5.82 kW, corresponding to a repetition rate of 88.8 MHz. These findings suggest that the Yb, Y: CaF₂-SrF₂ crystal shows promise as a new type of laser material, providing valuable insights for advancing disordered materials and incorporating other rare earth ions.