Coherent combining of high average power nanosecond pulse laser beams

Four high average power, high repetition rate, ns pulse laser beams have been coherently combined by single-detector, binary-tree filled-aperture coherent beam combining technique. For the present photonic crystal fiber based MOPA system, over 400 Watts combined average output power with 0.75 combining efficiency has been obtained. Combining efficiency degradation sources have been identified and its dependence on some specific misalignments discussed.