Group delay locking of coherently combined broadband lasers

We demonstrate a method for single-detector coherent sensing and automated coalignment of group delays in a coherently combined laser array, enabling robust coherent combining of broadband sources despite initial path mismatches exceeding the laser coherence length. The method is based on Fourier-domain filtering of the coherently combined laser beam to extract error signals, and it is equally applicable to controlling both spatial and temporal misalignments.