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Large optical nonlinearity at short‐wavelength‐infrared (SWIR) has enabled 2D MXene to be used explosively in ultrafast nonlinear photonics and optoelectronics. Despite the high technological interest in V4C3 MXene in electrochemistry, investigations from a nonlinear photonics perspective have yet to be conducted. Here, the nonlinear optical characteristics of V4C3 MXene at SWIR wavelengths are systemically investigated. First, Z‐scan measurements are performed and the saturated absorption and self‐defocusing properties of V4C3 MXene at both wavelengths of 1560 and 1910 nm are observed. Density functional theory calculation shows metallic characteristics of V4C3 MXene. Based on the saturable absorption properties of V4C3 MXene, a single saturable absorber (SA) operating at both wavelengths of 1560 and 1910 nm is experimentally implemented. Stable mode‐locked pulses of 638 fs pulse duration at 1559.9 nm are produced instantaneously from an erbium‐doped fiber ring cavity using SA. The same SA generates 1.08 ps mode‐locked pulses at 1911.9 nm from the thulium holmium co‐doped fiber ring cavity. This indicates that the operating bandwidth of this realized V4C3 MXene‐based SA could be at least 350 nm. This work strongly suggests that V4C3 MXene can serve as an ultra‐broadband and high‐performance nonlinear optical material platform in the SWIR regions.

An experimental investigation into the nonlinear optical properties of rhenium diselenide (ReSe2) was conducted at a wavelength of 1.9 μm using the open-aperture and closed-aperture Z-scan techniques for the nonlinear optical coefficient (β) and nonlinear refractive index (n2) of ReSe2, respectively. β and n2 measured at 1.9 μm were ~ − 11.3 × 103 cm/GW and ~ − 6.2 × 10–2 cm2/GW, respectively, which to the best of our knowledge, are the first reported measurements for ReSe2 in the 1.9-μm spectral region. The electronic band structures of both ReSe2 and its defective structures were also calculated via the Perdew–Becke–Erzenhof functional to better understand their absorption properties. A saturable absorber (SA) was subsequently fabricated to demonstrate the usefulness of ReSe2 for implementing a practical nonlinear optical device at 1.9 μm. The 1.9-μm SA exhibited a modulation depth of ~ 8% and saturation intensity of ~ 11.4 MW/cm2. The successful use of the ReSe2-based SA for mode-locking of a thulium–holmium (Tm–Ho) co-doped fiber ring cavity was achieved with output pulses of ~ 840 fs at 1927 nm. We believe that the mode-locking was achieved through a hybrid mechanism of saturable absorption and nonlinear polarization rotation.

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