1.95 μm kHz-linewidth single-frequency fiber laser using self-developed heavily Tm3+-doped germanate glass fiber.

We demonstrated a kHz-linewidth single-frequency laser at 1.95 μm using the self-developed heavily Tm(3+)-doped single-mode germanate glass fiber with the net gain coefficient of 2.3 dB per centimeter. The maximum output power of the stable single longitudinal mode continuous wave laser is over 200 mW. The slope efficiency measured versus the absorbed pump power is 34.8%, the signal-to-noise ratio is higher than 68 dB and laser linewidth is less than 7 kHz. A wavelength-tuning from 1949.55 to 1951.23 nm was also demonstrated based on changing the tension on the fiber Bragg grating outside the cavity.