This article introduces the composition, working principle and application of different wavelengths of fiber lasers.

Fiber lasers are mainly composed of pump source, coupler, rare earth-doped fiber, resonator and other components. The pump source is composed of one or more high-power laser diodes. The pump light emitted by the pump is coupled into the rare-earth element doped fiber as the gain medium through a special pump structure, and the photons at the pump wavelength are absorbed by the doped fiber medium to form The number of particles is reversed, and the stimulated light wave is fed back and oscillated by the resonator mirror to form a laser output. Now to introduce several wavelengths of fiber lasers.

The longest one is near 2.8 μm (Ho3+, Er3+ doped fiber laser, this band fiber laser has potential applications in biology, medical and other fields. In addition, 2.8 μm fiber laser can also be used as a pump light source for mid- and far-infrared lasers, using Er3+ The 4I11/2→4I13/2 of the ion and the 5I6→5I7 transition emission of the Ho3+ ion can obtain a laser output with a wavelength near 2.8 μm. Since the laser emission near 2.8 μm requires the host material to have low phonon energy and high optical transmission Therefore, fluoride glass is generally used as the fiber matrix.

Followed by fiber lasers around 2.0 μm (doped with Tm3+, Ho3+), 2.0 μm lasers are eye-safe lasers and are widely used in meteorological monitoring, laser ranging, lidar, and remote sensing. In addition, water molecules have a strong mid-infrared absorption peak near 2.0 μm. Using this band of lasers for surgery is conducive to accelerating blood coagulation and reducing surgical trauma. Mid-infrared fiber lasers also have important applications in the fields of medical and life sciences. The laser-activated particles output by the mid-infrared laser near 2.0 μm are mainly Tm3+ and Ho3+ ions. Using the 3F4→3H6 transition emission of Tm3+ ions and the 5I7→5I8 transition emission of Ho3+ ions, laser outputs with wavelengths around 2.0 μm and 2.1 μm can be obtained, respectively.

Next is the fiber laser near 1.5 μm (Er3+ doped, Er3+/Yb3+), since the laser output wavelength is located near the 1.5 μm optical communication window of the silica fiber, the laser output performance of Er3+ doped and Er3+/Yb3+ co-doped glass fiber is studied in depth , the development of fiber lasers around 1.5 μm has been relatively mature.

At present, the shortest is the fiber laser near 1.0 μm (Yb3+, Nd3+), and the fiber laser near 1.0 μm has been widely studied due to its application in fiber communication, laser guidance, frequency-doubling laser light source, pump light source and other fields. The doped rare earth ions in fiber lasers around 1.0 μm mainly include Yb3+ ions and Nd3+ ions. The laser emission of Nd3+ ions 4F3/2→4I9/2 was realized in Nd3+ ion-doped fiber, and the laser wavelength was tunable within 900~945 nm. Then, with the improvement of laser pumping light source, Yb3+ ion-doped fiber laser was successfully developed, and the tuning range of its laser output wavelength reached 1.01~1.16 μm.