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 (PtSe) 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 PtSe reveal efficient saturable absorption property at around 3 µm showing a modulation depth of 8.54% and a saturation intensity of 0.074 GW/cm. By introducing the bulk-like PtSe-SA into the Ho/Pr 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 PtSe-SA was also verified utilizing the same experimental setup after 40 days of ambient storage of the PtSe sample. The results not only validate the excellent nonlinear optical performance of PtSe, but also indicate that the bulk-like PtSe is a promising long-term stable SA material under ambient conditions for nanosecond pulse generation in the 3-µm mid-infrared spectral region.