Coherent beam combining of high-power tapered amplifiers

We describe the coherent beam combining of three high-power tapered laser amplifiers seeded by a DFB laser at λ = 976 nm, and demonstrate a combined power of 12.9 W in a close to diffraction-limited beam at a combining efficiency of > 65%. We use individual devices on C-mounts in a multi-arm interferometer. The phase pistons of each beam are matched by automatically controlling the ridge current of the amplifiers. Increased power per element was achieved by making use of a simplified, efficiently cooled single emitter-based optical system.