Miniaturized Mid-Infrared All-Fiber Laser Passively Q-Switched by Topological Insulator Bi2Se3

Conventional Q-switched mid-infrared fiber lasers normally rely on bulk optical elements for assembling mid- infrared resonators, which will possibly undermine the reliability and robustness of the fiber laser systems. Here, we address the challenge through demonstrating, for the first time, a miniaturized 3 μm Ho
³⁺
:ZBLAN fiber laser passively Q-switched by topological insulator Bi
₂
Se
₃
. The linear all-fiber cavity simply consists of a home-made 1153 nm fiber laser as pump source, a 2- m Ho
³⁺
:ZBLAN fiber, and two fiber end-facet mirrors. By inserting the few-layer Bi
₂
Se
₃
saturable absorber into the laser cavity, stable mid-infrared Q-switched pulses at 2920.6 nm were generated at a low threshold of ~70 mW, and the pulse repetition rate can be linearly tuned from 24.97 to 56.13 kHz. The maximum average power obtained was 315 μW, corresponding to the narrowest pulse duration of 1.54 μs and the maximum pulse energy of 6 nJ, relatively.