Enhanced nonlinear optical response of Se-doped MoS₂ nanosheets for passively Q-switched fiber laser application

An enhanced nonlinear optical (NLO) performance was observed in Se-doped MoS₂ nanosheets synthesized through a facile annealing process. Se-doped MoS₂ nanosheets with a large saturable intensity and high modulation depth generated stable passively Q-switched fiber laser pulses at 1559 nm. In comparison with the Q-switched fiber laser utilizing the pristine MoS₂ nanosheets as a saturable absorber, the passive Q-switching operation based on Se-doped MoS₂ nanosheets could be conducted at a lower threshold power of 50 mW, a wider range of repetition rates from 28.97 to 130 kHz, and a higher SNR of 56 dB. More importantly, the shortest pulse duration of 1.502 μ s was realized and the output power and pulse energy reached 17.2 mW and 133.07 nJ, respectively. These results indicate that tailoring the chemical composition of optical nanomaterials by introducing a dopant is a feasible method of improving the NLO response of the MoS₂ nanosheets and realizing excellent ultrafast pulse generation. (paper)