SINGLE-FREQUENCY THULIUM-DOPED DISTRIBUTED-FEEDBACK FIBER LASER
A single-frequency thulium-doped distributed-feedback fiber laser is demonstrated. A laser cavity based on a 36 mm long π-phase-shifted fiver Bragg grating (FBG) is inscribed in a heavily doped Tm fiber. Single-frequency radiation with a wavelength of 1919 nm and the maximum output power of 80 mW is generated at the 1.1 W pump power. The lasing linewidth is measured to be about 70 kHz. The relative intensity noise does not exceed 70 dB/Hz with the maximum at a frequency of 1.2 MHz.