Study of high power CBC fiber laser systems with non-equal splitting ratio beam-splitters

High power coherent beam combination (CBC) with non-equal splitting ratio beam splitters (BS) is studied. A BSbased two-channel CBC laser system has been built, and experiments with 50:50 BS and 30:70 BS has been carried. It shows that, when the inject laser power are the same, the combining efficiency decreases obviously as the ratio of the BS increases. The perfect combining efficiency can be resumed by adjusting the power ratio to be the same as the splitting ratio of the BS. A theoretical model has been established to further analyze the effect of the BS ratio quantitatively. For the condition of two equal inject power, the deviation of splitting ratio should be less than 9% to maintain 1% allowance for combining loss. The work can provide useful guidance for high power BS-based CBC laser sources.