Semi-metallic PtTe2 nanosheets are used as saturable absorbers to generate passive mode-locked pulse laser in the 2 μm band

In passively modulated pulse lasers, the highly stable saturable absorber (SA) used to generate passive pulsed lasers is a necessary core device. In this paper, layered PtTe2 nanosheets were fabricated using a simple, efficient, and low-cost liquid phase exfoliation (LPE) method, and PtTe2-SA devices were prepared by spin coating. Nonlinear optical tests show that the layered PtTe2 nanosheets have good nonlinear saturable absorption characteristics in the 2 μm band, with a modulation depth of 8.2 %, a saturated light intensity of 3.72 MW/cm2, and a non-saturated loss of 9.8 %. We introduced PtTe2-SA devices into Tm3+ doped solid-state laser for the first time, achieving passive mode-locking (PML) operations. In PML operation, a short pulse output of 670.8 ps was achieved. After being exposed to the air for 20 days, it can still produce good pulse output under the same experimental device. The results show that semi-metallic PtTe2 is expected to become a highly stable SA candidate material for pulsed solid-state lasers, which can be used to generate short pulse output in the 2 μm band, providing huge production power in many fields.