Breaking the symmetric spiral spectrum distribution of a Laguerre-Gaussian beam propagating in moderate-to-strong isotropic atmospheric turbulence

We demonstrate that the spiral spectrum (also known as orbital angular momentum spectrum) of a Laguer re -Gaussian (LG) beam with topological charge (TC) l is asymmetrically broadened propagating through moderate -to -strong atmospheric turbulence, even the statistics of turbulence is isotropic. This phenomenon is quite different from that predicted in weak turbulence where the spiral spectrum of a disturbed LG beam is symmetric with respect to its TC number l. An explicit analytical expression of the spiral spectrum of the LG beam with l = 1 is derived based on the extend Huygens-Fresnel integral and quadratic approximation, which is used to illustrate the transition scenarios of the spiral spectrum from symmetry to asymmetry in weak -to -strong turbulence. The physical mechanism for the asymmetric spiral spectrum in moderate -to -strong turbulence is thoroughly discussed. Our results are confirmed by the multi -phase screen numerical simulations and are consistent with the experimental results reported in Phys. Rev. A 105, 053513 (2022) and Opt. Lett. 38, 4062 (2013). (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement