Optical Coherent Combining in Multi-Aperture Free-Space Receivers through Atmospheric Turbulence via Optically Computed Alignment Gradients

Multi-aperture reception converts spatial diversity into a coherent-combining gain, but only if the relative phase and polarization of the collected field replicas are aligned before they are summed. In a satellite-to-ground downlink the atmosphere perturbs amplitude, phase and polarization, so the