Fiber Optic Amplifier Pump Combiners with Signal Feed Throughput

ABSTRACT: For this SBIR topic, we have proposed a novel high-power optical fiber pump combiner design that addresses the specific challenges associated with counter-pumping large-mode-area (LMA) double-clad gain fibers. Based on modeling and design optimization, we will fabricate kilowatt capable power combiner prototypes for pump coupling to double-clad Yb-doped polarization-maintaining (PM) fiber. We will characterize the prototype feed-though combiners using both axial refractive index profiling and a newly developed fiber-mode-analysis (FMA) measurement technique. This characterization will be used to determine the signal loss and modal transformation through the device. These unique characterization techniques will be used to fully understand and optimize the design and manufacturing processes for this new class of high-power feed-through pump combiners. BENEFIT: The successful completion of Phase I will validate the proposed novel design concept for high-power feed-though pump combiners. It will also establish unique characterization techniques that can be used in a subsequent Phase II effort that will optimize and develop the design and manufacturing methods required for reliable deployment in future military and commercial applications. High-power, feed-though fiber combiners are a critical enabling technology for the implementation of advanced multi-kilowatt fiber laser systems, for which there are numerous military and commercial applications.