Nonlinear optical response of niobium telluride and its application for demonstrating pulsed fiber lasers

Niobium telluride (NbTe2), a kind of few-layer two-dimensional (2D) transition metal dichalcogenides (TMDs) material, has been theoretically predicted with nonlinear absorption properties and excellent optical response. Herein, we experimentally demonstrated an Er-doped fiber (EDF) laser based NbTe2 as saturable absorber (SA). Few-layer NbTe2 nanosheets were successfully prepared by adopting the commonly used liquid-phase exfoliation (LPE) method. The nonlinear optical response of highly stable few-layer NbTe2 was investigated through an open-aperture Z-scan laser measurement, the nonlinear absorption coefficient was 2.45 × 10−11 m/W. Both Q-switched and mode-locked operation centered at 1 559 nm were recorded based on NbTe2 SA. The pulse duration was varied from 4.88 μs to 1.75 μs, and the adjustable range of repetition frequency is changed from 44.01 kHz to 64.12 kHz in passively Q-switched operation. Furthermore, a constant repetition rate of 5.33 MHz and pulse width of 2.67 ps were observed in mode-locked operation. Our experimental results fully reveal the nonlinear optical properties of NbTe2 used in pulsed fiber lasers and broaden its ultrafast applications in the optics field.