Target-in-the-loop Wavefront Sensing and Control with Collett-Wolf Beacon

It is well known that atmospheric turbulence can severely degrade performance of various optical systems including the laser beam projection systems discussed here. These systems are designed to create and maintain a laser spot of the smallest possible size on a remotely located object in the atmosphere. Compensation (mitigation) of turbulence effects in the laser beam projection systems is typically performed using adaptive optics (AO) wavefront correctors. In several applications the outgoing beam scattering off an extended object rough surface results in strong speckle modulation of the return wave. This speckle modulation is the major problem for the existing AO wavefront control techniques. In this paper we consider a new approach for speckle-effect mitigation in adaptive laser beam projection systems by creating an incoherent beacon (Collett-Wolf beacon) using either the projected beam itself or a single auxiliary laser illuminator beam. Using numerical simulations and bench-top experiment we show that using the Collett-Wolf beacon it is possible to mitigate speckle effects and achieve a high degree of turbulence compensation and increase of the laser beam brightness.