Low-threshold 1150  nm single-polarization single-frequency Yb-doped DFB fiber laser

We demonstrate a stable single-polarization single-frequency distributed feedback Bragg (DFB) fiber laser at 1150 nm based on a 5 cm long Yb-doped fiber which, to the best of our knowledge, is the first demonstration of a Yb-doped fiber-based single-frequency laser with a wavelength longer than 1120 nm. The threshold is as low as 10 mW. The measured maximum output power is 10.6 mW, and the spectrum at the highest power shows an excellent optical signal-to-noise ratio of about 70 dB, considering the amplified spontaneous emission in a short wavelength. The polarization extinction ratio is 25 dB, and the spectral linewidth is 20 kHz. This fiber laser is suitable for seeding high-power 1150 nm narrow-linewidth laser amplifiers, which can be used as high brightness pump sources for rare-earth-doped fiber lasers and Raman fiber lasers, or to generate visible radiation in the yellow spectral range, facilitating medical and astronomic applications.