Research On Side-pump Technique With Graphite Filament Heating Method

Fiber laser is widely used in communication,processing and military etc.Pump coupler is an important device of fiber laser.As it can couple the pump into the fiber of large moda field,the performance of pump coupler directly affects the final power output and beam quality.The research of side-pumped coupling technology is of great significance for the future of fiber laser.There are two methods of pump couplers which are end pump and side pump.End pump technology can easily achieve kilowatts power output of laser,but it has some drawbacks,for example,uneven gain distribution,limited fiber length and serious thermal effect,etc.However,side pump uses the side of double cladding fiber to pump coupling into the inner cladding.It does not take the ends of fiber and makes the pump distribution more uniform.This way solve the problems of end pump.This paper will be based on the side pump coupling technology research.We will dicsuss four aspects in detail: the theoretical simulation,the preparation of coupler,the parameter optimization of coupler performance and the application of coupling technology.The main contents and achievements of this thesis include the following aspects:1.The technology of side-pumped coupling by tapered fiber bundles based on graphite filament heating method was developed independently.The test method of performance of the side coupler was introduced;2.An(2 + 1)× 1 side-pump coupler was developed by using double-clad passive optical fiber.The performance of the side coupler is optimized by theoretical analysis and experiment.Finally,a coupler with the coupling efficiency of 95% and the forward and reverse signals light insertion loss of 0.03 d B and 0.05 d B respectively was obtained;3.An(2 + 1)× 1 side-pump coupler was developed by using gain fiber.The theoretical and experimental analysis was carried out to obtain a pump coupler with coupling efficiency higher than 90% and signal light leakage ratio less than 2%;4.The scheme of developing a side-pump coupler with triple-clad passive optical fiber is proposed.The relationship between the light conversion efficiency and the fiber length is found.Finally,the pump coupling efficiency and signal light insertion loss are 89% and 0.02% respectively;5.An all-fiber lasers with resonant cavity structure are built by self-developed coupler.The influence of forward,backward and double-ended pumping on the efficiency of the fiber laser are analyzed theoretically and experimentally.The influence of two kinds of pumping methods on laser efficiency and beam quality is analyzed experimentally.