Graphene-Bi₂Te₃ heterostructure as broadband saturable absorber for ultra-short pulse generation in Er-doped and Yb-doped fiber lasers

A new type of broadband saturable absorber made of graphene-Bi₂Te₃ heterostructure was reported, which synergistically combines light-matter interaction in graphene with that in a small bandgap semiconductor material Bi₂Te₃ to achieve an improved broadband nonlinear optical response. The graphene-Bi₂Te₃ heterostructure films were grown by chemical vapor deposition with 15% Bi₂Te₃ coverage on graphene, in which most of the Bi₂Te₃ nanoplatelets are less than 30 nm thick. It is interesting to find that the heterostructure thin film shows broadband saturable absorption property. At the communication band (around 1560 nm), the saturable intensity and modulation depth are measured to be 4.95 MW/cm² and 18.98%, respectively. While around 1067 nm, the corresponding saturable intensity and modulation depth are experimentally measured to be 2.61 MW/cm² and 23.11%, respectively. By incorporating this optical saturable absorber inside either an Er-doped or Yb-doped fiber laser, we are able to generate ultra-short pulse with very stable operation at 1565.6 and 1049.1 nm. Our experimental results clearly demonstrate that the graphene-Bi ₂Te₃ heterostructure can be a promising broadband nonlinear optical material for broadband ultra-fast laser photonics.