Atmospheric turbulence sensing with structured terahertz beams containing orbital angular momentum.

Clear-air turbulence poses a persistent hazard to aviation, yet it evades conventional weather radar and remains difficult to detect. Existing optical sensing methods falter under severe turbulence and are extremely vulnerable to misalignment between airborne nodes. Here we introduce an atmospheric sensing scheme built on structured terahertz (THz) beams carrying orbital angular momentum (OAM). We derive and experimentally validate an analytical model that maps turbulence-induced OAM modal crosstalk to the refractive index structure constant of the atmosphere. Our simulations and experiments demonstrate that this THz-OAM approach remains robust under severe turbulence where optical systems saturate, and offers orders-of-magnitude greater misalignment resilience. Furthermore, this scheme also enables localization of the dominant turbulent clusters through understanding the interaction of diverging THz-OAM beams with the turbulent medium in the reciprocal propagation paths and simultaneously monitoring water vapor to identify turbulence precursors. This work establishes structured THz-OAM beams as a robust framework for remote atmospheric turbulence inference.