Generation Of Airy Beam Arrays Based On A LCoS Device And Research On Their Scintillation Characteristics

Airy beam arrays,as a new type of non-diffraction beam arrays,have a combination of the property of wavefront disturbance resistances of Airy beams and the advantage of space diversity technology,and have an effective inhibition on the scintillation effect causing by the atmospheric turbulence.Which make sure that stabilization on the beam power links of the laser propagation systems in atmosphere insisting of free space laser communication,lidar and laser weapon.In this thesis,based on the high precision wavefront simulation using a compensated LCoS device,the generation method of Airy beam arrays based on a Fresnel holographic lens method is investigated,the scintillation characteristics of Airy beam arrays in different turbulent conditions are study,and the functions of the coherences between the constituted beams in Airy beam array o f the inhibitory effects on scintillation effect are investigated.The main contents to investigate are as follows:(1)Dynamic propagation of 4-beamlets Airy array is simulated using the mathematical model of Airy beam arrays.The scintillation characteristics of Airy beam arrays are study and the scintillation index is used to measure the strength of scintillation effect.The methods to calculate the sc intillation index,including theoretical analytical method,numerical simulation method and experimental method,are compared.Thus,the experimental method using an LCoS device is chosen to investigate the functions of Airy beam arrays on scintillation effect.(2)An improved method to generate Airy beam arrays based on a Fresnel holographic lens method is proposed,and the different number Airy beam arrays using a compensated LCoS device are obtained,Detailed works are as follows:a)Beginning from the transform principle of thin lens,the optical transform relationship between the phase plane and the image plane is deduced.In a strict sensu,the irradiance on the front surface of the lens is the square of the Fourier transform on the complex amplitude of the beam is proved.b)The effects of aberrations on the Fresnel holographic lens method are investigated in simulation.Results show that 3? spherical aberration causes the diffraction of Airy beam increasing 1.9 times,the propagation trajectory and intensity distribution are also changed.Thus,a improved method to measure the phase retardance curves of LCoS devices is proposed.Based on the method,a multipoint calibration approach is used to compensate the inherent wavefront aberration of LCoS devices,resulting in the precision of plane wavefront simulation reaches 0.14?(PV value).c)The different numbers of Airy beam arrays are obtained using a compensated LCoS device through moving the central position and rotating the direction of the Airy beam phase mask.(3)The phase screen is numerically simulated using the power spectrum inversion method,and the atmospheric turbulence dynamic simulation system which can simulated strong,moderate,and weak scintillation strength atmospheric turbulences is constructed.The scintillation characteristics of Airy beam arrays are study utilizing this system.Results show that Airy beam arrays work better than a single Airy beam on reduction of scintillation effect,and the scintillation indices of 4-beamlets Airy array are 0.46,0.298,and 0.3 times of single Airy beam in strong,moderate,and weak scintillation conditions,respectively.(4)Incoherent and coherent Airy beam arrays are study from the partially coherent theory.The incoherent and coherent 2-beamlets Airy arrays are generated through extending the spectrum width of light source and increasing the space optical path difference.The functions of the coherences between the constituted beams in Airy beam array of the inhibitory effects on scintillation effect are investigated.Results show that the scintillation indices of incoherent Airy beam array are 0.9,0.83,and 0.71 times of coherent Airy beam array in strong,moderate,and weak scintillation conditions,respectively,which illustrates that the reductions of the coherences between the constituted beams in Airy beam arra y can further resist the scintillation effect.