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In this Letter, we demonstrate a mode-locked Er-doped fiber laser incorporating antimony telluride (Sb 2 Te 3) topological insulator (TI) as a saturable absorber (SA). The laser was capable of generating 270 fs-short soliton pulses at 1560 nm wavelength, which are the shortest solitons generated with a TI-based saturable absorber so far. In order to form a saturable absorber, a bulk piece of Sb 2 Te 3 was deposited on a side-polished single-mode fiber with the presence of a low refractive index polymer. Such saturable absorber exhibits modulation depth at the level of 6% with less than 3 dB of non-saturable losses. Our study shows that TI-based saturable absorbers with evanescent field interaction might compete with SAs based on carbon nanomaterials, like graphene or nanotubes. Additionally, thanks to the interaction with the evanescent field, the material is not exposed to high optical power, which allows to …