Hollow optical pin-like beam based Cassegrain system performance enhancement under atmospheric turbulence

Cassegrain system, widely used in laser ranging systems, faces emission efficiency challenges due to central obstruction. Current methods utilizing hollow beams based on orbital angular momentum (OAM) aim to mitigate these effects. However, such beams maintain the hollow structure, leading to an ineffective target illumination. Far-field center-healing hollow beams, such as hollow Gaussian beams (HGBs), can effectively address these problems to ensure a proper target illumination but are distorted by atmospheric turbulence, resulting in a reduced echo intensity. In this study, hollow optical pin-like beams (HOPBs) are experimentally demonstrated for the first time, to the best of our knowledge, with superior turbulence resistance. Based on hollow beams, the emission efficiency of the central obstruction system increases from 72.45% to around 90%. The minimal echo decline of HOPBs is only 15% under moderate turbulence, significantly outperforming HGBs, which experience reductions exceeding 31%. Even under strong turbulence, HOPBs maintain a minimal echo reduction (41.19%). This study highlights the advantages of HOPBs in addressing limitations from both central obstruction and atmospheric turbulence, offering a promising solution for improving the performance of laser ranging systems.