Operation of a multidither COAT system with a continuous-surface deformable mirror

Abstract

The use of multidither coherent optical adaptive techniques (COAT) is rapidly gaining acceptance as a useful tool for removing phase distortions that are introduced on a transmitted laser beam by its associated optical system or by the atmosphere. Earlier multidither COAT system demonstrations1,2 have used planar segmented-aperture piston mirrors for both the phase dither and phase correction functions. High-power laser applications will require continuous-surface mirrors for both the dither and correction functions. The operating characteristics of COAT systems employing deformable mirrors are expected to be significantly different from systems that utilize segmented, pistonlike mirrors. In particular, the deformable mirror can introduce significant coupling between control channels, it can point the entire beam rather than merely changing the transmitted beam phase front in a stepwise manner, and it can cause the servo system to converge with detrimental 2π phase ambiguities in the error signal.