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Stimulated Brillouin scattering (SBS) in a high-Q resonator is capable for narrow-linewidth laser generation for various applications but is limited by on-resonance pump to SBS matching from single-longitudinal lasing. In this Letter, we present a narrow linewidth laser via SBS that is enhanced in a monolithic high-Q fiber resonator. The unique cross-polarization pump scheme based on fiber birefringence prevents high-order SBS and ensures single-frequency Brillouin lasing with high intracavity conversion efficiency. Fundamental linewidth of 50 Hz is achieved. Moreover, our scheme also allows precise characterization of Brillouin frequency shift and gain bandwidth of some nonlinear materials. [ABSTRACT FROM AUTHOR]

A self-injection locking scheme has the potential to narrow the linewidth of lasers in a compact setup. Here, we report a narrow linewidth laser source near 1 μm by the self-injection locking scheme using a Fabry–Pérot (FP) hollow resonator with a high-quality factor (Q > 108). The measured fundamental linewidth of the laser is 41 Hz, and a coarse tuning range over 5.5 nm is achieved by changing the driving current of the laser source. Meanwhile, a fine-tuning range of 373 MHz is achieved without mode hops by changing the voltage applied to the PZT on the resonator. More importantly, benefiting from the low thermal refractive noise and low thermal expansion of the FP hollow resonator, the beat-note linewidth and the frequency Allan deviation are measured to be 510.3 Hz in and 10−11 (1 s of averaging time), respectively, by using a fully stabilized frequency comb as a reference. Such a high-performance laser is fully integrated with a palm-sized package (52.3 ml) for field-deployable applications. [ABSTRACT FROM AUTHOR]