Rotational velocity measurement under the influence of atmospheric turbulence

Due to their unique helical wavefront structure and orbital angular momentum (OAM) properties, vortex beams have demonstrated remarkable potential in applications measuring rotational velocity utilizing the rotational Doppler effect (RDE). Distortion induced by atmospheric turbulence in remote velocity sensing, however, poses a significant challenge to their practical implementation. This paper examines, through both simulation and experiment, the influence of turbulence-induced mode dispersion on the RDE for OAM superposition states. Key effects analyzed include waveform distortion and the broadening of rotational Doppler shift (RDS) peaks in the frequency domain. The results show that the velocity measurement error caused by turbulence distortion increases from 0.34% to 1.06%. The increase in turbulence intensity exacerbates the degree of OAM mode dispersion, leading to a notable decrease in the RDS amplitude and a concurrent rise in the sideband amplitude. This work not only elucidates the turbulence-induced degradation mechanisms in RDE-based sensing but also provides a foundation for improving the robustness of remote velocimetry systems under real-world conditions.