We demonstrated a high-repetition-rate Q-switched fiber laser with topological insulator Bi₂Se₃ absorber. The absorber was made into a film structure by spin-coating method using few-layer Bi₂Se₃ nano-platelets which had regular shape. The uniform film had a low saturable optical intensity of 11 MW/cm(2), which is the lowest saturable optical intensity in the saturable absorbers made by topological insulator till now. By inserting the absorber film into an Erbium-doped fiber laser, a high-repetition Q-switched laser with the repetition rates from 459 kHz to 940 kHz was achieved. The maximum output power was 22.35 mW with the shortest pulse duration of 1.9 μs. To the best of our knowledge, both of the repetition rate and the output power were the highest values among the Q-switched fiber lasers with topological insulator absorber.

We demonstrated an all-normal-dispersion Yb-doped mode-locked fiber laser based on tungsten disulphide (WS 2 ). The saturable absorbers (SA) were made by mixing WS 2 solution with polyvinyl alcohol (PVA), and then evaporated on a substrate. The modulation depth of the WS 2 film was 2.06% and the saturable optical intensity was 71.6 MW cm −2 . When the WS 2 film was inserted into the fiber laser, the mode-locked pulses with pulse width of 2.5 ns and repetition rate of 2.84 MHz were obtained. As the pump power increased to 350 mW, the maximum output power was measured to be 8.02 mW. To the best of our knowledge, this is the first time to realize mode-locked pulses based on WS 2 -SA at 1 μm waveband.

Wavelength switchable and dual-wavelength soliton operations are demonstrated in an erbium-doped fiber laser with three pieces of TI Bi 2 Se 3 polyvinyl alcohol (Bi 2 Se 3 -PVA) film. Wavelength switchable operation from 1532 to 1557 nm could be achieved just by adjusting the pump power. With the appropriate settings of PC and pump power, a novel dual-wavelength soliton operation was observed. The dual-wavelength pulses operate at different mode-locked states. One is the single pulse mode-locking operation at 1532 nm, and the other one is the bound-soliton states at 1557 nm. However, the dual-wavelength soliton operation cannot be stable for a long time. The numerical results demonstrate that the separations of bound pulses have small variation and the different phase of bound pulses appear jumping change of . Index Terms-Fiber lasers, Mode-locked lasers, Bound solitons, Dual-wavelength solitons, Topological insulator.

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We demonstrate a passively Q-switched Yb:LSO laser based on tungsten disulphide (WS 2 ) saturable absorber operating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating method. With low speed, the WS 2 nanoplatelets embedded in polyvinyl alcohol could be coated on a BK7 glass substrate coated with high-refractive-index thin polymer. The shortest pulse width of 1.6 µs with a repetition rate of 76.9 kHz is obtained. As the pump power increases to 9 W, the maximum output power is measured to be 250 mW, corresponding to a single pulse energy of 3.25 µJ. To the best of our knowledge, this is the first time to obtain dual-wavelength Q-switched solid-state laser using few-layer WS 2 nanoplatelets.