All-normal-dispersion dissipative-soliton fiber laser at 1.06 µm using a bulk-structured Bi₂Te₃ topological insulator-deposited side-polished fiber

We experimentally demonstrate a 1.06-µm dissipative-soliton fiber laser incorporating a saturable absorber based on a bulk-structured Bi₂Te₃ topological insulator (TI). The saturable absorber, which had a bulk-structured Bi₂Te₃ TI film deposited on a side-polished fiber, provided the dual functions of nonlinear saturable absorption and spectral comb filtering, which are essential for the generation of dissipative solitons. The saturable absorption function was obtained through a micrometer-thick bulk-structured Bi₂Te₃ TI film, whereas the spectral comb filtering function was through the asymmetric side-polished fiber structure, on top of which a different refractive index film was deposited. The ∼17 µm-thick Bi₂Te₃ TI film was prepared using a simple mechanical exfoliation method. The fabrication of the targeted micrometer-thick bulk-structured film was straightforward without needing special care, compared to nanosheet-based film fabrication. Stable dissipative-soliton pulses with a composite temporal shape were readily obtained by incorporating the prepared saturable absorber into an ytterbium-doped fiber ring cavity with all-normal dispersion. The temporal width of the output pulses was measured to be ∼230 ps. (paper)