Reverse saturable absorption in Ti3C2 MXene nanosheets for dissipative soliton resonance mode-locking operation in Er-doped fiber laser

In this paper, Ti3C2Tx MXene nanosheets were prepared using a low-power ultrasonic-assisted liquid phase exfoliation method. The Ti3C2Tx nanosheets based saturable absorber deposited on the tapered microfiber possessed the typical saturable absorption and reverse saturable absorption with the surface evanescent field. With a home-made femtosecond excitation source at 1550 nm, the modulation depth was determined as 4.8% with a saturation intensity of 18.7 MW/cm2. By inserting our as-prepared saturable absorber into an Erbium-doped fiber laser (EDFL), two types of mode-locked pulses operating in the stable conventional soliton (CS) and dissipative soliton resonance (DSR) regimes were realized at the fundamental repetition frequency of 7.39 MHz, respectively. The pulse width of the CS pulse was 1.185 ps with a central wavelength of 1560.6 nm. While the pulse width of the DSR pulses varied from 2.07 ns to a maximum of 8.13 ns with the increase of the pump power. Our work reveals the reverse saturable absorption effect of Ti3C2Tx could play a key role in the DSR pulse generation, which may benefit the application of the pulse modulation and optical communication with the two-dimensional materials.