Radial sub-aperture coherence method used to achieve beam steering with high precision and stability

Sub-aperture coherence (SAC) algorithm, which is based on the classical phase modulation method called variable period grating (VPG), was usually used to control liquid crystal optical phased arrays (LCOPA) to achieve agile beam steering with high precision. However, the beam steering angle of SAC is severely affected by the beam aperture, which limits the generality of the algorithm distinctly. In this article, two kinds of new phase modulation method have been proposed to solve this problem, which were named as radial sub-aperture coherence (RSAC) and symmetrical radial sub-aperture coherence (SRSAC). By using RSAC, the holistic drift of steering angle, which is caused by the variation of beam aperture, can be effectively avoided. In addition, a series of equidistant steering points with ultra-high precision can be obtained. Upon this basis, SRSAC greatly enhances the steering angle's stability in the presence of system alignment error and relative vibration. Thus, the practicability of LCOPA for beam steering can be improved effectively.