Wavefront Sensing for High Scintillation Environments

Strong scintillation in long horizontal path laser beam projection systems, such as ABL, corrupts the phase difference measurements made with a Hartmann sensor by causing non-uniform illumination of the sub-apertures, hence, non-uniform noise effectsacross the wave front sensor. Strong scintillation can also cause branch points in the beacon field making the wave front reconstruction and correction processes difficult because they lack the continuous phase map required in most wave front correctionschemes. We propose a shearing interferometer wavefront sensor and a new wavefront reconstruction algorithm insensitive to the branch points. Our new approach will provide accurate phase recovery in a high scintillation environment. Phase I develops asimulation code and reconstruction algorithm and evaluates the performance of this innovative technique.We expect a detailed simulation code for the static shearing interferometer and a new phase reconstruction algorithm will be developed and the feasibility of the proposed approach will be evaluated for various ABL propagation scenarios in highscintillation environment. This effort heralds development of a new wavefront sensing capability which will enable expansion of ABL missions for longer range and lower elevation operations and forms a basis for commercial wavefront sensors for lasercommunication systems.The proposed scintillation resistant wavefront sensor and reconstructor have both military and commercial applications. Besides the ABL, a static shearing interferometer can also be used in Relay Mirror, remote sensing and atmospheric imaging programs. Ashearing interferometer wavefront sensor proposed here may also result in significant improvements in the performance of active ground-based satellite imaging systems. The proposed approach can also lead to the development of a commercial wavefrontsensor. This sensor would be used in commercial low-order AO systems to mitigate atmospheric effects in high data rate optical communication channels. A shearing interferometer developed under this program can be a key element in this system.