3  ×  1 all-fiber signal combiner with high beam quality for high-power lasers

An all-fiber signal combiner is an essential component to break through the incoherent beam output power limitation of fiber laser power. So far, the high-power signal combiners reported before usually had output core diameters of higher than 100 µm with NAs of 0.22, leading to serious beam quality degradation. In order to improve the beam quality, a 50 µm core diameter output fiber with a smaller NA of 0.12 is utilized in this work. We have theoretically made a detailed simulation of the combiner. Combiners with three 20/400 µm input fibers are fabricated, and three ~1064 nm fiber lasers with a maximum output power of over 2 kW have been used as the input light source. A maximum output power of up to 6.06 kW was achieved by incoherent beam combining, and the final output power was 6.06 kW with a beam quality factor (M ²) of 3.69. To our best knowledge, it is the first report on a multi-kW class laser based on a beam combiner with an M ² of less than 4. (paper)