Milliwatt-level single-mode laser from an erbium-doped silica microcavity using a fiber Brillouin amplifier

Microlasers based on ultrahigh-quality-factor erbium-doped silica microcavities are renowned for their exceptionally low thresholds and remarkably narrow linewidths. However, these microlasers struggle to achieve single-mode operation while delivering high output power, which presents a significant barrier to their widespread practical application. Here, we fabricate an erbium-doped silica microsphere cavity with the ultrahigh-Q factor (exceeding 10⁸). By employing non-resonant pumping within the 980 nm band, a multimode laser with a remarkably low lasing threshold of just 32 µW at the 1550 nm band is realized. Then, by using a fiber Brillouin amplifier, only one single peak of the multimode laser is selectively amplified. Therefore, a single-mode laser is achieved, with a power of 63 mW, a signal-to-noise-ratio of 40.5 dB and a side-mode-suppression-ratio exceeding 62.6 dB.