Research On In-band Pumped Nd-doped Double-clad Polarization Maintaining Fiber Laser

The1.06μm near-infrared region laser is one of the earliest researchedwavelengths in laser field. It could be wildly used in laser ranging, medical scienceresearch, optical spectrum research, life science research, laser processing, astronomyresearch, defense&military industry and many other fields. In-band pumped (includedirect pumped and thermally boosted pumped) Nd-doped double clad fiber laser is thehigh quality1.06μm laser source as its features of high output power, super beamquality, excellent heat dissipation and compact structure.In this dissertation, we analyzed and experimental researched the1.06μm outputperformance of the880nm direct pumped and888nm thermally boosted pumpedNd-doped double clad polarization maintaining fiber lasers and compared the outputperformance with808nm traditional pumped Nd-doped double clad polarizationmaintaining fiber laser to show the superiority of the in-band pumped method.The main contents are as follow:1. Analyzed the inner structure of the double clad fiber and the working principle ofthe double clad fiber laser; Illustrated how the inner clad shape affects the pumplight’s absorption efficiency; Described several pump light’s coupling methodsand compared their advantages. Introduced the practical cavities of double cladfiber laser.2. Analyzed the Nd-doped fiber’s energy level structure; Utilizing the four-levelsystem, we deduced the output performance of the808nm traditional pumped andin-band pumped Nd-doped double clad fiber lasers, determined the optimizedfiber length in experiment and calculated the heat generation of the laser systems.3. The output performance of the880nm direct pumped Nd-doped double cladpolarization maintaining fiber laser was experimental researched. The maximumoutput power of4.61W was obtained while the13.85W pump power was coupledin the fiber and7.85W pump power was absorbed by the fiber core, with a lowthreshold power of73mW and a conversion efficiency of60.19%, whichperformed better than the808nm traditional pumped method whose showed athreshold power of approximately80mW and a conversion efficiency of52.96%4. The output performance of the888nm thermally boosted pumped Nd-doped double clad polarization maintaining fiber laser was experimental researched. Themaximum output power of3W was obtained while the11.28W pump power wascoupled in the fiber and5.1W pump power was absorbed by the fiber core, alsowith a low threshold power of70mW and a relatively high conversion efficiencyof60.93%, which performed better than traditional pumped method and directpumped method.5. The polarization performance of this fiber laser system was measured. Thedegrees of polarization of three different pumped schemes were0.818,0.796and0.812respectively, which indicated good polarization maintaining property of thelaser system.