Single-polarization single-frequency Yb³⁺-doped fiber laser at 1156 nm via dynamic Bragg grating mode selection

We demonstrate a single-polarization single-frequency Yb³⁺-doped fiber laser operating at 1156 nm using a 10-m-long unpumped Yb³⁺-doped fiber (YDF) as a dynamic saturable absorber (SA). Leveraging spatial hole-burning-induced refractive index modulation, a self-adaptive Bragg grating with sub-MHz bandwidth is formed, enabling ultranarrow linewidth single-longitudinal-mode lasing. The linear cavity design with bidirectional pumping achieves an output power of 20.4 mW, > 65 dB optical signal-to-noise ratio, and <0.36% power instability. With a polarization extinction ratio of 22 dB, relative intensity noise below -139 dB/Hz (above 0.1 MHz), and a linewidth less than 10 kHz, this laser bridges the gap between long-wavelength operation and high coherence in Yb³⁺ laser systems, offering a compact source for ¹⁷¹Yb optical clocks, dermatological therapy, and mid-infrared pump applications.