Preparation of a Novel Semiconductor BiCuOS and Its Application in Long-Term Stable Mode-Locked Fiber Lasers

The novel semiconductor bismuth copper oxysulfide (BiCuOS) exhibits significant potential in optoelectronics due to its exceptional environmental stability, high carrier mobility, and narrow bandgap. These superior physical properties also render it advantageous for applications in ultrafast photonics. However, to date, there has been no research reported on BiCuOS in ultrafast fiber lasers. In this work, BiCuOS was synthesized by the low-cost hydrothermal method. Then, a BiCuOS-based saturable absorber (SA) was fabricated using the optical deposition method and incorporated into an Er-doped fiber laser (EDFL). Stable mode-locked pulses with a pulse width of 608 fs were achieved. It is worth noting that the results show that the spectral drift can be ignored after several hours of continuous operation, and the long-term evaluation results show excellent stability. After storage for nearly 12 months, BiCuOS-SA still maintains good and stable mode-locking performance, and the output pulse width is still in the femtosecond range. These results indicate that BiCuOS has excellent thermal and environmental stability, making it an excellent candidate for long-life ultrafast photonic devices.