Subaperture Adaptive Optics for directed energy phased arrays

ABSTRACT: The proposed research will develop a method of compensating atmospheric disturbances in the transmitting subapertures of a phased array transceiver operating in the infrared. The aero-optical boundary layer and atmospheric turbulence create phase variations within each subaperture. To compensate these variations, an adaptive optical system will be used in each subaperture. The proposed wavefront sensor is a self-referencing interferometer, and the corrective element is a liquid crystal adaptive optic or other device suitable for use in phased arrays. The beacon for the wavefront sensor is the coherent high energy spot reflected from the target of the phased array. The main innovation in the proposed research consists of techniques to mitigate the corruption in the beacon phase caused by speckle, and other related difficulties associated with using the reflected spot as a beacon. The speckle phase that the phasing system estimates will be used to compensate the speckle phase in the adaptive optics system. BENEFIT: The primary product of this research will be the conceptual design of an adaptive optical (AO) system suited for use in phased array transceivers. This system will be available in future phased array design work to improve the performance of phased arrays as needed. The adaptive optical system will not depend on a particular phased array architecture, but will be available for use with a wide variety of architectures. The primary capability of the AO system will be in correcting the aero-optical boundary layer for airborne phased arrays. The use of the AO system also allows for more efficient configurations of the beam phasing system.