Mo_4/3B₂T₂-based saturable absorber for generating conventional and bound-state solitons in erbium-doped fibre laser

As a new two-dimensional (2D) material, Mo_4/3B₂T₂ has attracted great attention due to its characteristic electrical and optical properties. However, the nonlinear optical properties of Mo_4/3B₂T₂ and its applications in the ultrafast photonics aspect have not been reported. In this work, we first demonstrate the nonlinear saturable absorption properties of 2D material Mo_4/3B₂T₂. The modulation depth and saturation absorption intensity of Mo_4/3B₂T₂ are 4.5 % and 534 MW/cm², respectively. Herein, conventional soliton and bound-state solitons were generated in a fibre laser in the 1.5-μm region after inserting the 2D material Mo_4/3B₂T₂ into the laser cavity as a saturable absorber (SA). A highly stable conventional soliton is observed at 1560.57 nm with a 3 dB bandwidth of 3.12 nm. The frequency rate, pulse width, and signal-to-noise ratio were 7.59 MHz, 1.08 ps, and 65.83 dB, respectively. In addition, the bound-state solitons are obtained at a pump power of 320 mW. The central wavelength, pulse interval and spectral modulation period of the bound-state soliton are 1560.9 nm, 6.1 ps and 1.33 nm, respectively. These results suggest that 2D material Mo_4/3B₂T₂ can be used as a promising SA in ultrafast and ultra-narrow photonics.