Spread and wander of multimode Hermite Gaussian beams in depth-dependent ocean turbulence

Abstract In this study, we derive an analytical expression of the cross-spectral density (CSD) function when multimode Hermite-Gaussian (mHG) beams propagate through ocean turbulence along slant paths. The integral transformation method for the CSD function of mHG beams can extend to other types of beams involving Hermite components, enabling accurate assessments of beam transmission quality. Furthermore, we explore the correlations between light intensity, beam spread, and beam wander, considering both the characteristics of the light source and the depth-dependent nature of oceanic turbulence. The results demonstrate that, by selecting an appropriate source size, mHG beams outperform Gaussian beams, exhibiting improved resistance to turbulence with reduced relative beam width and beam centroid shift. These results provide essential theoretical insights for optimizing the performance of mHG beam transmission in underwater wireless optical communication (UWOC) systems, contributing to the design of more robust and reliable UWOC links.