Influence of polychroism and decentration on spreading of laser beams propagating in non-Kolmogorov turbulence

摘要

Taking the mean-squared beam width, the angular spread, the Rayleigh range and the turbulence distance as characteristic parameters, the spreading of partially coherent polychromatic decentered laser beams propagating through non-Kolmogorov turbulence is studied. The influence of the bandwidth Ω of spectrum, the beam decentered parameter β, and the fractal constant α of the atmospheric power spectrum on the beam spreading is examined in detail. It is found that polychromatic laser beams are less sensitive to turbulence than monochromatic ones, and decentered laser beams are less sensitive to turbulence than centered ones. The larger the Ω and β are, the larger the beam spreading is in free space, but the less the beam spreading is affected by turbulence. In turbulence laser beams with different values of β will have the same directionality if the angular spread is chosen as the characteristic parameter of beam directionality, which is quite different from the behavior in free space. The beam spreading is largest and the influence of turbulence on the beam spreading is also largest when α is in a region about 3.1. In addition, the dependence of the turbulence distance on Ω and β is also investigated, and some interesting results are obtained.