摘要： Black phosphorus (BP) ranks among the most promising saturable absorber materials for ultrafast pulse generations at 2 μm. However, the easy-to-degrade characteristic of BP seriously limits the long-term operation of ultrafast fiber lasers and hence becomes a bottleneck for its relevant practical applications. In this paper, a modified electrochemical delamination exfoliation process was explored to produce high-performance, large-size and oxidation-resistance BP nanosheets, where BP nanosheets in high yield with evenly coated tetra-n-butyl-ammonium (TBA) organics by precisely controlling the intercalation chemistry can be obtained. A mode-locked Tm/Ho co-doped fiber laser with high temporal stability and long-term operation capability was demonstrated based on the innovatively-fabricated BP saturable absorber. The self-starting mode-locking operation featuring high signal-to-noise ratio of 58 dB and long-term stability has been verified for at least three weeks, which indicates the successful passivation of the employed synthesis method. These results fully indicated that passivated BP is an efficient candidate in 2 μm range ultrafast photonics field, which will promote the ultrafast optical application of BP and also other infrared photonic and photoelectronic devices.