Study On Transmission Characteristics Of Airy Beam In Underwater Turbulence Field

Laser communication technology has the advantages of large communication capacity,good security,economical and portable equipment.It has potential application value in the field of marine communication.Due to the existence of temperature,salinity stratification and the velocity field formed by the wind force on the surface of the ocean,the actual ocean turbulence field is complex and the intensity is anisotropic.Laser communication can be affected by underwater turbulence,resulting in beam spread,beam wander and scintillation that hinder the transmission of light.As a kind of special beam with no diffraction,Airy beam has the excellent characteristics of non-diffraction,selfhealing and self-bending which are not possessed by traditional Gaussian beam,and makes it attract scholar's attention in the application of anti-turbulence effect.Based on the ocean turbulent refractive index power spectrum which is more suitable for ocean turbulence and easy to calculate.The paper studies the spread,wander and scintillation characteristics of Airy beam in long-distance transmission under weak turbulent conditions.Comparison of transmission characteristics with Gaussian beams in the same turbulent flow field.The physical expression of the extended beam characteristics of Airy is obtained by the method of cross-spectral density.The variation of beam propagation characteristics with different beam parameters and turbulent field intensity parameters is obtained by numerical simulation.The simulation and experimental results of turbulent phase-screen method based on power spectrum inversion are used to verify the relationship between beam expansion characteristics,turbulence intensity and beam parameters.The beam expansion characteristics of the Airy beam and the Gaussian beam under the same transmission conditions are compared to verify the reliability of the beam expansion theory and numerical simulation.Starting from the mean squared displacement of the instantaneous centroid of the beam wander,a new turbulent refractive index power spectrum model is obtained by geometrical optics approximation to obtain the physical expression of the Airy beam wander after the disturbance of the ocean turbulence,numerically simulating different truncation factors,the main lobe size and turbulence intensity parameters vary with the transmission distance.Simulation and experiments verify the effects of beam wander theory and numerical simulation by discussing the effects of different beam parameters and turbulence intensity parameters on the beam wander characteristics of Airy and Gaussian beams,respectively.According to the first order Rytov approximation of the weak turbulence condition,the expression of the scintillation coefficient characterizing the intensity of the light intensity is obtained,and the numerical simulation of the light scintillation coefficient under different correlation parameters is carried out.From the simulation and experiment under the different physical conditions,the received plane light intensity distribution after random phase screen perturbation,using self-programming to process and extract the light intensity scintillation coefficient verification theory and numerical simulation results under different physical parameters,and the Airy beam is compared to the intensity of the Gaussian beam under the same conditions.Comparing the spread,wander and scintillation of the transmission simulated and experimental Airy beam and Gaussian beam,it is found that the Airy beam has an advantage over the Gaussian beam in resisting the turbulence effect.Which provides theoretical support for the use of Airy beams instead of traditional beams in the field of marine optical communications.