Long-term stable platinum diselenide for nanosecond pulse generation in a 3-µm mid-infrared fiber laser

In this paper, we fabricate the bulk-like multilayer platinum diselenide (PtSe₂) and employ it as saturable absorber (SA) for a passively Q-switched fiber laser operating at 2865 nm for the first time, to the best of our knowledge. The nonlinear optical measurements of the bulk-like multilayer PtSe₂ reveal efficient saturable absorption property at around 3 µm showing a modulation depth of 8.54% and a saturation intensity of 0.074 GW/cm². By introducing the bulk-like PtSe₂-SA into the Ho³⁺/Pr³⁺ co-doped ZBLAN fiber laser, stable Q-switched pulses with a duration as short as 620 ns are achieved at the pulse repetition rate of 238.1 kHz. The maximum average power is 93 mW, corresponding to a peak power of 0.63 W. The excellent long-term stability of the PtSe₂-SA was also verified utilizing the same experimental setup after 40 days of ambient storage of the PtSe₂ sample. The results not only validate the excellent nonlinear optical performance of PtSe₂, but also indicate that the bulk-like PtSe₂ is a promising long-term stable SA material under ambient conditions for nanosecond pulse generation in the 3-µm mid-infrared spectral region.