Spiral spectrum of Laguerre-Gaussian beams under atmospheric turbulence and pointing errors

The spiral spectrum appears to be extended when the Laguerre-Gaussian beam is applied to atmospheric laser communication due to the turbulence effect and the misalignment of the receiver. In this paper, the spiral spectrum expansion of the Laguerre-Gaussian beam turbulence effect and the receiver misalignment is studied. Mathematical derivation and numerical simulation are used to study the analytic expression of the spiral spectrum of the lateral and the oblique inclination at the receiver under turbulence. The results show that the transmission distance has a nonlinear effect on the diffusion of the spiral spectrum. After reaching a certain transmission distance, the diffusion will suddenly increase and eventually stabilize. With the increase of turbulence intensity, the diffusion of spiral spectrum increases, and the increase rate is related to the transmission distance. The effect of transverse offset distance on the spiral spectrum is related to the turbulence intensity, and finally stabilizes. And the greater the angle of inclination of the receiving end, the more serious the spiral spectrum diffusion.