Research On Beam Coupling Of Double-Clad Fiber Lasers

Emergence of double-clad fiber lasers is a turning point in the history of the development of fiberlaser, which makes high-power fiber laser output possible. In order to further improve the output powerof double-clad fiber lasers, we can do in many ways, the pump coupling and the influence of double-clad fiber with different inner-clad shapes on absorption efficiency are studied in this article.This article has designed two laser diode coupling systems. First, we use a cut fiber as acylindrical lens for LD reshape. Fiber cut along different locations result different shaping influence,use Matlab software to simulate the different shapes of the fiber cylindrical lens for LD imaging,results show that the shape works best when fiber is cut along the diameter direction; Second, alsousing fiber for cylindrical lens for LD fast axis reshape, but the cylindrical lens isn’t cut, immediatelybehind the cylindrical lens is a spherical end face of fiber. Using Zemax software to optimize differentstructural parameters, and do tolerance analysis of systems, then we consider all kinds of system errorsby Monte-Carlo analysis method, we can know: all the coupling efficiency of the system are above75%, the probability that coupling efficiency greater than80%is88.8%. This article also analyses theinfluence of bending fiber on coupling efficiency, the smaller the fiber bending angles, the larger thebending radius, the higher the coupling efficiency of the system will be.The inner-clad shape of double-clad fiber has significant impact on the absorption efficiency ofpump light, respectively using Matlab and Zemax software in this article to calculate different cladshape of the pump light absorption efficiency, Results show that circle absorption efficiency is thelowest, only10%; rectangle and octagonal in short fiber length can reach98%. And Zemax simulationresults show the pump light is absorbed mainly in the extent of a few centimeters of the fiber end, thisis also why fiber laser cooling mechanism is focused on the end, these calculations have some referencevalue for the actual manufacture of fiber lasers.