Novel two-dimensional semi-metallic NiTe2 based saturable absorber for ultrafast mode-locked fiber laser

•Few-layer NiTe2 nanosheets are prepared by combining the convenient chemical synthesis and liquid phase exfoliation.•Two-dimensional semi-metallic NiTe2 exhibits saturable absorption properties, which has been seldom reported.•Er-doped and Tm-doped mode-locked fiber lasers are realized using NiTe2-based tapered fiber saturable absorber, respectively.