Integrated Fiber-Optic Device Based on a Combination of a Piezoelectric Transducer and a Bulk-Structured Bi2Te3 Topological Insulator for Q-Switched Mode-Locking of a Fiber Laser

We propose a single, integrated fiber-optic device that possesses both passive Q-switching and active mode-locking functions. The structure of the integrated fiber-optic device consists of a bulk-structured Bi
₂
Te
₃
topological insulator (TI) layer sandwiched between the surface of a piezoelectric transducer and the flat side of a side-polished fiber. The Bi
₂
Te
₃
TI is used as a saturable absorption material to induce Q-switching while the piezoelectric transducer is used to produce an acousto-optical modulation function for mode-locking. The integrated fiber-optic device is used within an erbium fiber ring cavity to readily produce stable Q-switched mode-locked pulses at 1559 nm. Control of the modulation index of the acousto-optic modulation part together with the pump power was also shown to be able to change the laser operating regimes among CW, Q-switching, Q-switched mode-locking, and mode locking.