Features of adaptive phase correction of optical wave distortion under conditions of intensity fluctuations

Abstract

For the first time the reason of loss of efficiency of adaptive phase correction at propagation of optical waves in turbulent atmosphere under conditions of strong intensity fluctuations is experimentally explained. According to the data of experiments performed both on horizontal and vertical atmospheric routes, it was found that when the radius of coherence in the optical wave becomes less than the first Fresnel zone, intensity fluctuations begin to affect the data of phase measurements. This results in the fact that the main meter of the adaptive optics (AO) system - Hartmann’s sensor - in the presence of deep amplitude modulation no longer provides the correctness of phase distribution measurements. Based on the study of the behavior of the modal components of the phase fluctuations reconstructed from the measurement data at different operating modes, it was found that, first of all, the lower modes of phase fluctuations decomposition - tilts, defocusing and astigmatism - are distorted and, as the analysis of these modes shows, they differ greatly from the classical modes corresponding to the mode of weak fluctuations.