CrTe₂ as a new saturable absorber for a passive mode-locking Er-doped laser

1T-CrTe₂ is one of the 2D transition metal chalcogenides (TMCs) and has attracted great attention in the field of spintronics due to its fascinating magnetic properties. Except for its performance in spintronics, the optical properties such as the nonlinear optical (NLO) characteristics of 1T-CrTe₂ have rarely been reported. In this paper, the NLO properties of CrTe₂ nanoparticles of 1.5 μm were investigated by using a Z-scan method. The nonlinear absorption coefficient and nonlinear refractive index were measured to be −(1.9) × 10⁴ cm GW⁻¹ and 0.93 × 10⁻³ cm² GW⁻¹, respectively, which indicate the excellent NLO properties of CrTe₂ nanoparticles. Furthermore, by depositing 1T-CrTe₂ nanoparticles on a side-polished fiber and inserting CrTe₂-SA into an Er-doped fiber laser cavity, a stable mode-locking laser with a pulse width of 568 fs was achieved, demonstrating the good potential of 2D-CrTe₂ in ultrafast photonics applications.