Manufacturing and optical characterization of side-pumped high power fiber combiner for LMA-fibers

Fiber laser and amplifiers are important for material processing, medical applications, telecommunication and metrology. Such laser systems need in addition to the active fiber itself several fiber-based components for the realization of compact, rugged and optically efficient monolithic fiber setups. A key component is an all-fiber pump combiner with signal feedthrough. The most common type of fiber combiner is a tapered fused fiber bundle (TFB) [1]. TFB combine highly efficiently pump light up to several hundred watts. The manufacturing of TFBs with signal feedthrough is very challenging, since the mode field overlap of the signal input (tapered fiber bundle) and the signal output (double clad fiber) has to be matched at the juncture between the bundle and the output fiber. This leads usually to a degradation of the beam quality and to transmission losses for the signal.