High-OSNR all-fiber microfiber laser based on high-gain erbium-doped fiber

The realization of microfiber lasers requires high-gain media. Here, a high-gain Er-doped fiber (EDF) was prepared, whose gain was up to 34 dB with a length of 0.5 m using a pump of 980 nm. By tapering home-made EDF via three-electrode discharge technology, a 2-μm-diameter active microfiber with < 0.5 dB tapering loss was fabricated, which was further shaped into a 670-μm-diameter microfiber knot resonator (MKR) exhibiting 0.76 nm free spectral range (FSR) and 14 dB extinction ratio (ER). The microfiber laser was constructed based on the MKR, which achieves 9.1 mW output power at 1531.4 nm with 50.7 dB optical signal-to-noise ratio (OSNR) and < 0.04 nm 3 dB bandwidth. The packaging technique enables stability: < 1.21% power fluctuation in 4 hours. This work overcomes the trade-off between power and stability in microfiber lasers, offering immediate applications in photonic chips, integrated light sources, and other fields.