Design and fabrication of > 20 KW 5 x 1 pump combiner with high efficiency

Design considerations and fabrication details of a high-efficiency 5 x 1 pump combiner with a brightness ratio of 1.05 are presented. Using five 135/155 mu m NA = 0.22 input fibers and a 310/341 mu m NA = 0.22 output fiber, the average efficiency of this 5 x 1 combiner is 98.71%, tested by a 915 nm laser diode (LD). In the case of using 1018 nm tandem-pumping laser as the test source, the combiner has been proved to have a transmission efficiency of not less than 99.95% for all 5 ports. Up to 20.91 kW combined power has been reached, and the temperature rise of the combiner is less than 10 degrees C at the highest output power, which demonstrates further power scaling ability by using pump source with higher power. OCIS codes: 140.3510,220.4610