The Intensity Distribution Of Partially Coherent Vortex Beam Propagation In The Atmosphere

The vortex beam can provide a new dimension in multiplexing, which has been attracted extensively attention in optical micromanipulation, biological optics, multiplex communication and other fields. The light beam emitted by the laser is usually partially coherent beam.Therefore, it is of great significance to study the intensity distribution of partially coherent vortex beam in atmospheric turbulence. In this paper, the intensity distribution of partially coherent vortex beam in atmospheric turbulence was studied. The main achievements were summarized as follows:1 . Based on the generalized Huygens-Fresnel principle and the cross spectral density function, the partially coherent Gaussian-Schell model (Gaussian-Schell Model, GSM) vortex beam was chosen as the object of this research. The complete analytical expression for the intensity distribution of the beam propagation in atmospheric turbulence was derived, and the condition for the propagation of the beam in free space was given, in addition, the condition of the coherent GSM vortex beam in atmospheric turbulence and free space was given.2 . According to the analytical expression of the intensity distribution, the intensity distribution of partially coherent GSM vortex beam and fully coherent GSM vortex beam propagating in atmospheric turbulence and free space were compared. Influence of beam intensity distribution is analyzed through the simulation analysis in atmospheric turbulence with different transmission distance, turbulence intensity, coherence length, topological charge, waist width and beam wavelength, and the physical interpretation of each result was given.3. Based on the modified Kolmogorov turbulence spectrum model, the Laguerre-Gaussian(Laguerre-Gaussian, LG) vortex beam was chosen as the object of this research. Using the basic theory and research method of partially coherent GSM vortex beam, the intensity distribution of partially coherent off-axis LG vortex beam propagating in atmospheric turbulence was derived.The influence of beam parameters, transmission distance and turbulence intensity on the moving distance and direction of the dark core and the broadening of the beam were simulated and analyzed. Some simulation results were verified by experiments.The results show that the partially coherent GSM vortex beam was more effective than the fully coherent GSM vortex beam in atmospheric turbulence. When the partially coherent GSM vortex beam was transmitted to a certain distance, the singularity of the beam disappears, and the intensity distribution was finally transformed from the hollow distribution to the Gaussian distribution. The dark core of partially coherent off-axis LG vortex beam changes with the change of transmission distance, turbulence intensity and beam parameters. The experimental results were in agreement with the partial simulation results.