Phase synchronization in tiled aperture coherent beam combining based on feedback from off-axis locations in far-field plane

Conventional tiled-array coherent beam combination (TA-CBC) systems typically rely on feedback from the central lobe of the far-field intensity pattern. In this work, we explore different off-center alternative feedback points and combinations of off-center points for feedback and experimentally demonstrate one of the simplest and reliable method. The simulation results are experimentally validated in a proof-of principle 7-channel hexagonally tiled-array system using a robust optical fiber-based light collection mechanism and stochastic parallel gradient descent (SPGD) algorithm for phase control. This approach is perhaps ideal for long-range target-in-loop systems as well as short-range CBC-based additive manufacturing systems, where the main lobe is interacting with the target and hence may not available for feedback.