Two-Dimensional Nano-PtTe₂ for Higher-Order Harmonic Mode-Locking Polarization-Locking Vector Soliton Ultrafast Fiber Laser

The unique physicochemical properties of nanomaterials have attracted much attention in the field of light modulation. Their small sizes enable them to be characterized by large edge ratios and high surface atom counts. These features make nanomaterials possess high light modulation efficiency. The two-dimensional (2D) nanomaterial PtTe2 (nano-PtTe2) is a typical transition metal dichalcogenides (TMD) material. The nano-PtTe2 has the advantages of narrow and tunable bandgap, excellent stability and easy exfoliation, and thus has good modulation capability for 1.5 μm lasers. We used the liquid-phase exfoliation (LPE) technique to obtain a dispersion of few-layer PtTe2 nanosheet. PtTe2-saturable absorber (SA) was obtained by optical deposition using a tapered optical fiber. The saturation absorption curve of PtTe2–SA was acquired by a self-constructed two-arm balanced detection system. The modulation depth of SA reached 6.6%, while the saturation absorption intensity measured 5.44 MW/cm2. Subsequently, we built a ring-shaped ultrafast fiber laser. Polarization-locking vector soliton (PLVS) of conventional soliton (CS) of 852 fs and PLVS of harmonic mode-locking (HML) of 82th order with repetition frequency of 638 MHz were realized. These results show that nano-PtTe2 has excellent nonlinear absorption properties, and nano-PtTe2 has the potential to be used in the application of multisoliton fiber laser systems applied in the fields of communication and optical detection et.al. Furthermore, the experimentally obtained PtTe2–SA has polarization-independent property, which helps to further study the vectorial properties of light.