Deterioration of laser beam quality caused by cladding modes in fusion splices of double-cladding fibers

Abstract

In this study, the influences of cladding modes on double-cladding fiber (DCF) laser beam quality are discussed for the first time. Based on mode-coupling theory and beam propagation method, the formations of DCF cladding modes and mixed fields of guided modes and cladding modes are discussed and illustrated under the conditions of core misalignment in fiber fusion splice process. Further, the deterioration of laser beam quality caused by the existence of cladding modes is also carried out. Simulation results show in good accordance with the experiment of M2 factor measurement of fiber lasers with cladding modes.