Research on high power (8+1)×1 pump-signal combiner

This paper presents the development of an (8+1)×1 pump-signal combiner with high pump coupling efficiency and negligible beam quality degradation. Compared to conventional (6+1)×1 combiner, the developed (8+1)×1 combiner features a smaller space occupancy for individual pump fibers, which makes the pump sources less prone to being affected by cladding light in the counter-directional pumping configuration. It also has a larger space occupancy for the signal fiber, which ensures better preservation of beam quality. The fabricated combiner exhibits a pump coupling efficiency of 98.9 %, a beam quality degradation ratio of less than 3%, and a temperature rise coefficient of less than3 °C/kW without active cooling. When this combiner is used in a counter-directional tandem-pumped fiber laser, it allows for a high beam quality output that exceeds 10 kW.