Stable multiwavelength Tm-doped fiber laser with a microfiber knot resonator

We presented a compact and enduring multiwavelength Tm-doped fiber laser at 2 mu m employing a microfiber knot resonator (MKR). The MKR, made by the flame-brushing technique, has a fiber diameter of 10 mu m and a ring diameter of 150 mu m. The MKR plays a role as both the comb filter and the power equalization device, which is critical for the stable multiwavelength Tm-doped fiber laser. By properly adjusting the pump power, three wavelength lasing channels (1956.2, 1964.4, and 1971.8 nm) were observed stable and their average power density was around -8.76 dBm with 1 W pump power. In addition, the channel spacing is 5.8 nm with the 3-dB bandwidth of the channel smaller than 0.5 nm. The experiments demonstrated that the MKR can be utilized as a comb filter with the suitable transmission spectrum to reach a steady multiwavelength Tm-doped fiber laser.