Spreading of spiral spectrum of Bessel–Gaussian beam in non-Kolmogorov turbulence

The analytical formulas for the spiral spectrum of Bessel–Gaussian (BG) beam and the channel capacity of a communication system based on orbital angular momentum (OAM) in non-Kolmogorov turbulence have been derived. The influence of the azimuthal index, wavelength, exponent parameter αα, inner scale and outer scale on spiral spectrum is investigated. Numerical results reveal that a spiral spectrum of BG beam in non-Kolmogorov turbulence is more affected by turbulence with larger azimuthal index, shorter wavelength, smaller inner scale and larger outer scale. It is demonstrated that the spiral spectrum also depends on the propagation distance and structure constant. The spiral spectrum of BG beam in non-Kolmogorov turbulence spreads significantly with the increasing of exponent parameter αα and spreads slightly after reaching a maximum point. It is showed that the variation of channel capacity of the OAM-based communication system, with respect to parameter α, has the same trend as the spiral spectrum.