Theory Research Of Srs Effect In High Power Double Cladding Ytterbium Doped Fiber Laser

So far, the output power of fiber laser more than kilowatts are using double cladding fiber doped by rare earth ion such as germanium, ytterbium, erbium and neodymium as the gain medium. The highest single mode output has achieved 10000 watts. And more than 100000 watts achieved for the multimode output. Fiber lasers are fairly common among the medical equipment field, industrial cutting field, high energy weapons field, and other areas of the cutting-edge technology.Factors affecting the continued ascension of output power are increasingly highlighted with the rapidly increase of the fiber laser output. The internal mechanical damage of optical fiber, the nonlinear effect and the fiber temperature will have a bad influence on the output characteristics, which seriously hindered the improvement of fiber laser output power. In this paper, we studied the nonlinear effect in continuous wave high power fiber laser, especially the stimulated Raman scattering (SRS). What we mainly explore are as follows:1. On the premise of continuous light, we only consider a first order SRS, and set up a basic dynamic model in the fiber laser, the fiber amplifier and the transfer fiber. Considering the interaction between the signal, pump and stokes light.2. The use of collocation method is used to solve the steady state coupled rate equations in the oscillator, the laser amplifier and the transfer fiber. We obtained the distribution of pump, signal and stokes light along the fiber axial. The output characteristics are also simulated.3. We wrote the simulation program using MATLAB, and designed the human-computer interaction interface. The system is totally automatic. An accuracy rate more than 90% is realized.4. Using the compiled software under the different condition of pump, we explored SRS in directly LD pump amplified, MOPA amplified and tandem pump amplified fiber laser. The effects of fiber laser structure parameters (such as area of active fiber cross section, fiber length, doping concentration, loss, etc.) and light source parameters (such as signal wavelength, the pump wavelength and way of pump, etc.) on SRS are also studied. The obtained data has important significance for the construction of the high power fiber lasers and amplifier.