▎ 摘　　要

NOVELTY - A quantum dot thin film based on a two-dimensional material comprises quantum dot such as graphene quantum dot, a topological insulator quantum dot, a transition metal sulfide quantum dot, and a black phosphorus quantum dot, where size of the quantum dot is not more than 10 nm. USE - Quantum dot thin film based on a two-dimensional material for a saturable absorber that is utilized in ultrafast passively mode-locked laser such as all-fiber laser or all-solid-state laser (all claimed). ADVANTAGE - The material has strong absorption to the laser in the energy band, and improved stability of the laser. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following: (1) a method for preparing quantum dot thin film based on a two-dimensional material (2) a saturable absorber (3) an ultrafast passively mode-locked laser.