Mo4/3B2T2/Co3O4 vdW heterostructure as saturable absorber for ultrafast pulse generation

Abstract

VdW heterostructure have garnered significant interest in ultrafast laser generation because of their attractive saturable absorption properties, holding promise for applications in optics, medicine, and optoelectronics. In this study, the saturable absorption of Mo4/3B2T2/Co3O4 vdW is investigated for the first time. Mo4/3B2T2/Co3O4 vdW SA is successfully applied to passively mode-locked Er-doped fiber lasers. Due to the excellent saturable absorption properties of Mo4/3B2T2/Co3O4 vdW SA, stable mode-locked fiber lasers can be realized in the same cavity, including fundamentally conventional soliton, bound soliton, and harmonic soliton. Among them, the conventional soliton operates at a repetition rate of 11.16 MHz with a high SNR of 56.26 dB. Bound soliton is observed with a soliton pulse separation of 5.26 ps. Furthermore, 3rd-, 5th-, 8th-, 10th-, 12th-, 15th-, and 17th-order harmonic solitons are observed, corresponding to repetition rates of 33.48 MHz, 55.8 MHz, 89.28 MHz, 111.6 MHz, 133.92 MHz, 167.4 MHz and 189.72 MHz, respectively. For vdW heterostructure, the saturable absorption properties are strongly modulated by the interlayer coupling, which may be introduced by the Fermi level recombination and photogenerated carrier migration between the heterostructure. We established a model to understand the saturable absorption properties of the Mo4/3B2T2/Co3O4, which suggests the enhancements of the saturable absorption are attributed to the carrier migration between Mo4/3B2T2 and Co3O4. The results indicate that Mo4/3B2T2/Co3O4 vdW heterostructure can be used as an excellent nonlinear optical material, which can be used as SA in ultrafast pulse generation.