Passively mode-locked red Pr:LiYF₄ laser based on a two-dimensional palladium diselenide saturable absorber

We report a passively mode-locked Pr:LiYF₄ (Pr:YLF) visible laser using a palladium diselenide (PdSe₂) as a saturable absorber (SA) for the first time, to the best of our knowledge. The nonlinear optical properties of two-dimensional (2D) PdSe₂ nanosheets in the visible band were studied by the open-aperture Z-scan technique. The results indicate the significant saturable absorption properties of PdSe₂ nanosheets in the visible region. Furthermore, the continuous wave mode-locked (CWML) visible laser based on PdSe₂ SA was successfully realized. Ultrashort pulses as short as 35 ps were obtained at 639.5 nm with a repetition rate of 80.3 MHz and a maximum output power of 116 mW. The corresponding pulse energy was 1.44 nJ and peak power was 41.3 W. These results indicate that 2D PdSe₂ SA is a promising high stability passively mode-locked device for ultrafast solid-state visible lasers.