Measuring the orbital angular momentum spectrum of vortex beam disturbed by turbulence

An experimental scheme based on interferometry is designed to measure the orbital angular momentum spectrum of vortex beam perturbed by turbulence. The orbital angular momentum spectrum of vortex beam can be calculated by using four light intensity images. The laser beam is modulated by a spatial light modulator to obtain a vortex beam, and then passes through another spatial light modulator loaded with a turbulent phase perturbation hologram to interfere with the reference beam. The orbital angular momentum spectrum of the vortex beam can be obtained by making use of two interference patterns and the intensity patterns of the vortex beam and the reference beam. The results show that the experimental scheme can measure the orbital angular momentum spectrum of the vortex beam affected by turbulence.