Adaptive Optics Compensation in Deep Atmospheric Turbulence

Adaptive optics (AO) compensation of deep atmospheric turbulence remains a significant obstacle to the deployment of laser beam projection and imaging systems for a many applications. Tactical high-energy laser (HEL) weapon systems will be particularly limited by inadequate AO schemes as they will often be required to operate in engagement scenarios encountering deep turbulence. AO systems that employ a Shack-Hartmann WFS are particularly hampered in strong turbulence due to the presence of branch cuts in the sensed phase function. MZA proposes to investigate a novel multi-conjugate AO system concept, model a prototype in a tactical HEL weapon system context, and evaluate its performance in strong turbulence via wave-optics and experimentation. The concept, named SIRCAO, utilizes an SPGD driven DM conjugate to a location along the propagation path and a second DM, conjugate to the pupil plane, driven by WFS outputs, where the WFS is a Shack-Hartmann or SRI. Beyond HEL cleanup, the SPGD DM provides an intensity remapping of the BIL return before it is sensed by the WFS by applying a phase change and then reimaging. This reduces branch cuts in the phase and allows for significant performance increase of the WFS and the overall system.