Novel (9+1)x1 taper-fused side pump and signal combiner for multi-kW fiber laser applications

Taper-fused side pump and signal combiners use direct fusion splices between tapered multi-mode pump fibers and a double-clad signal fiber, eliminating fusion-splice points and ensuring low signal insertion loss and excellent spatial beam quality. Unlike traditional end-pump couplers, the side-coupler design accommodates more pump arms. Last year, we demonstrated the (6+1)×1 taper-fused side pump and signal combiner, achieving a 97.98% coupling efficiency at 2230 W. As a further step, we increased the number of pump arms to 9, boosting the pump power capacity. Using Rsoft BeamPROP for 3D simulations, we optimized performance, achieving a theoretical coupling efficiency for higher-order modes like LP87, with leakage power below 0.13%. We also successfully manufactured a compact (9+1)×1 combiner overcoming fabrication challenges. Integrating these side-pumping combiners into multi-kW or specialty fiber lasers will further unlock the advantages of side-pumping technology.