Design Of The Segmented Cladding Fibers And Analysis Of Ytterbium Doped Fiber Lasers

Thanks to their high luminance, favorable dissipating of heat, high conversionefficiency, high beam quality and compactness, the fiber amplifiers/lasers have beendeveloped rapidly. Especially, the application area of the fiber lasers has beenextended into high power industries, which make the study of the fiber laser becomea focus. Large mode fibers and cladding pumping technology are effective methodsto increase the output power of the fiber lasers these years. The reports beforeindicate that when the fiber has a large mode area, the beam quality decreases, Thesegmented cladding fibers (SCF) as a new microstructure fiber have both large modearea and high beam quality and will be a good idea for high power lasers. In thispaper, we first introduce the dependence of segmented cladding fibers’ characters,including the effective index distribution, the guided mode of the0level and theeffective fundamental mode area on the fiber parameters. With the increase of theoutput power, it becomes more and more crucial to control of the nonlinear andthermal effects. The effects of temperature on the characters of Ytterbium-dopedsegmented-cladding fiber lasers (YDSCFLs) are discussed numerically at the sametime. The research contents mainly include:1. The methods including the radial effective index method (REIM), thetransmission matrix method and the finite element method which are used to analyzethe SCF are introduced firstly. Then, with the methods of the radial effective indexmethod (REIM) and the transmission matrix method (TMM), the dependence ofsegmented cladding fibers’(SCF’s) characters including the effective indexdistribution, the guided mode and the effective fundamental mode area on thestructure parameters (the segmented number, the index difference, the duty cycle andthe core radius) of the fiber are systematically analyzed.2. Based on the rate equation theory, the effect of the fiber parameters (thesegmented number, the index difference and the duty cycle) on the Yb3+dopedsegmented cladding fibers amplifiers is numerically analyzed. At the same time, the temperature-dependent rate equation for Yb3+doped segmented cladding fiberslasers based on Boltzmann distribution is built. And the effect of the temperature onthe fiber lasers’ output for three pumping method (forward pumping, backwardpumping and double-side pumping) is numerically discussed.