All-fiberized, passively Q-switched 1.06 μm laser using a bulk-structured Bi_2Te3 topological insulator

We experimentally demonstrate the use of a bulk-structured Bi _2Te3 topological insulator (TI) deposited on a side-polished fiber as an effective saturable absorber for the implementation of an all-fiberized passively Q-switched 1.06 μm fiber laser. Unlike previous Q-switched laser demonstrations based on nanosheet-based TIs, which require complicated and sophisticated fabrication procedures, a ∼9.1 μm-thick bulk-structured Bi_2Te3 TI film that was prepared using a mechanical exfoliation method was chosen to be used in this experimental demonstration due to ease of fabrication. The modulation depth of our prepared bulk-structured Bi _2Te3 TI-deposited side-polished fiber was measured to be ∼2.5% at 1.06 μm. By incorporating such an absorber in an all-fiberized ytterbium-doped fiber ring cavity, stable Q-switched pulses were obtained through evanescent field interaction between the oscillated beam and the Bi _2Te3 TI film. The temporal width and repetition rate of the output pulses were tunable from ∼1 to ∼1.3 μs and from ∼77 to ∼35 kHz, respectively, depending on the pump power. Through a performance comparison of our laser with recently demonstrated Q-switched 1 μm fiber lasers using carbon nanotubes, graphene, and nano-structured TIs, our bulk-structured Bi _2Te3 TI-based saturable absorber is shown to have passive Q-switching performance comparable to saturable absorbers based on carbon nanotubes or nano-structured TIs.