Mikhail A. Vorontsov, (U.S. Army Research Laboratory), Jim F. Riker (AFRL/DESM, Air Force Research Laboratory), Ernst Polnau (Univeristy of Maryland), Svetlana L. Lachinova (Univeristy of Maryland), V. S. Rao Gudimetla (AFRL/DESM, Air Force Research Laboratory)
Keywords: Lasers
Abstract:
We present the concept development of a novel atmospheric compensation system based on adaptive tiled fiber array (ATFA) operating with target-in-the-loop (TIL) scenarios for directed energy applications. The ATFA system is integrated with adaptive beam director (ABD) with wavefront control and sensing functions performed directly on a beam director telescope primary mirror. The ATFA beam control aims to compensation of atmospheric turbulence-induced dynamic phase aberrations and a corresponding extended target brightness increase. The system is specifically designed for tiled fiber system architectures operating in strong intensity scintillation and speckle-modulation conditions typical for extended targets and includes both local (on-tile) wavefront distortion compensation and phase locking of sub-systems. The compensation algorithms are based on adaptive optimization of performance metrics. Local wavefront distortion compensation is performed using on-tile stochastic parallel gradient descent (SPGD) optimization of local speckle metrics directly measured on each fiber-tile. Phase locking is performed using SPGD optimization of a composed metric, that is, the metric combined from local metrics. An experimental setup is developed to evaluate the feasibility of controlling beam quality by using speckle metrics based on the temporal analysis of the speckle pattern of light which is backscattered from an extended target and recorded by a single photo detector. The experimental setup is used to investigate beam quality improvement, adaptive process convergence speed, and the influence of target shape.
Date of Conference: September 10-14, 2006
Track: Lasers