Fabrication and Output Characteristics of an (18+1)×1 Polarization-maintaining Pump and Signal Combiner for a High-power Fiber Laser

In this paper a pump combiner, a key component of a high-power fiber laser, was fabricated, and its output characteristics measured using a high-power performance measuring instrument. The (18+1)×1 pump combiner consists of an optical-fiber bundle of one signal fiber and 18 pump fibers, an output optical fiber, and housing. The signal and output fibers were fabricated using polarization-maintaining optical fiber. By measuring the loss of signal light along the tapering length of the optical-fiber bundle, the tapering length was optimized to 18 mm. Signal-light insertion loss, pump-light transmittance, and polarization extinction ratio of the fabricated (18+1)×1 pump combiner were measured as 6.5%, 98.07%, and 18.0 dB respectively. The temperature distribution of the pump combiner, at a high power of 2 kW using 18 pump laser diodes, was measured and analyzed using a thermal-imaging camera.