▎ 摘　　要

NOVELTY - Saturable absorber comprises graphene and composite nanosheets loaded on the graphene, where the composite nanosheets comprise bismuth telluride nanosheets, and ring-shaped antimony telluride nanosheets surrounding the bismuth telluride nanosheets and contacting the bismuth telluride nanosheets to form a heterojunction. USE - The saturable absorber is used in saturated absorber device (claimed) for electricity, and optical and thermoelectric device. ADVANTAGE - The saturable absorber is easy to agglomerate, easy to be oxidized, and has improved saturable absorption performance. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: a method for preparing the saturable absorber, which involves providing graphene oxide dispersion liquid and bismuth telluride nanosheet, adding antimony source, tellurium source, second reducing agent, and second surfactant to a second solvent to obtain a second mixed liquid, adding the bismuth telluride nanosheets and graphene oxide dispersion to the second mixed solution, and reacting at a second preset temperature for a second preset time to obtain the saturable absorber; and a saturable absorber device comprising an optical fiber and the saturable absorber carried on the core end face of the optical fiber, or a broadband dielectric film and the saturable absorber arranged on the broadband dielectric film.