Nonlinear Absorption and Refraction Properties of V₄C₃ MXene and its Use for an Ultra‐Broadband Saturable Absorber

Abstract 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.