Ultrasmall 2D NbSe2 based quantum dots used for low threshold ultrafast lasers

Ultrasmall NbSe2 quantum dots (QDs) with an average diameter of 2.68 nm were successfully fabricated and investigated. By employing the NbSe2 quantum dots (QDs) as a saturable absorber, highly stable ultrafast laser pulse trains with a duration of 765 fs or 380 ps were successfully generated from mode-locking erbium or ytterbium-doped fiber laser systems by using the fabricated NbSe2 QDs. The obtained laser pump power threshold for the mode-locking operation of the Er-doped fiber laser was 15 mW, which is the lowest value recorded among 2D materials based saturable absorbers. Our results give a promising contribution to the research field by demonstrating the strong nonlinear optical properties of these novel ultrasmall NbSe2 QDs. It also opens up new opportunities for the use of these novel materials for nonlinear optics and ultrafast laser photonic technologies.