Study On The Theory Of Laser Beam Propagating Through Atmosphere And Its Application In The Fourier Telescope System

Fourier telescopy is a new active coherent imaging technology, which uses large area receiver to receive energy information returned from the target and employs the phase closure techniques to eliminate the phase fluctuation caused by atmospheric turbulence, for high resolution imaging of the distant dim objects. The theory of laser beam through atmosphere is one of the important basic theories of Fourier telescope, especially the atmospheric turbulence effect, which seriously affects the imaging performance of Fourier telescope. In all the forms of laser beam, Flat-topped Gaussian beam have potential advantage application in Fourier telescope. When propagating through atmosphere, it shows uniform near-field energy and concentrated far-field energy. At the same time, research has shown that it is affected by atmospheric turbulence smaller than Gaussian beam, moreover the higher the order of the flat-topped beam is, the less it affected by turbulence. For now flattened Gaussian light turbulence theory is not yet perfect, this paper made a deep research on the theory of flat-topped beam through turbulence. At the same time, the effect of atmospheric turbulence on the Fourier telescope and the suppression algorithm were studied, and the application of flat-topped beam to the system is presented based on the research of flat-topped beam theory and simulation.Specific work is as follows:First, the theory of Gaussian beam propagating through atmospheric turbulence was researched. The scintillation of Gaussian beam through non-Kolmogorov turbulence phase screen with arbitrary thickness and position was deduced, and a dimensionless ratio was obtained by being equiva lent to scintillation of the expanded atmospheric turbulence. By using this ratio, a new method of using phase screen to accurate simulate real atmospheric turbulence scintillation was proposed.Second, the theory of flat-topped Gaussian beam propagating through atmospheric turbulence was simplified. Based on analysis method of Laser beam propagation in atmosphere turbulence, the simplified model of the second-order statistical moments of flat-topped beam were established by using appropriate variable transformation. The weighted average relationship between the turbulence theory of flat-topped beam and Gaussian beam was revealed. It laid a foundation for further theory research of flattened Gaussian optical propagation in turbulence.Third, the scintillation theory of flat-topped Gaussian beam in the nonKolmogorov turbulence was improved. On-axis scintillation formula of flat-topped Gaussian beam was derived with generalized von Kármán power spectrum model, and its variation trend with the turbulence inner scale was analyzed. O ff-axis scintillation of flat-topped Gaussian beam in the long distance transmission of non-Kolmogorov turbulence was studied. Its variation with the off-axis distance, the power law, the flat-topped order and the parameters of the incident propagation were analyzed, with the conclusion of the smaller scintillation of flat-topped beam on the larger incident parameter0?.Fourth, the effect of atmospheric turbulence on Fourier telescope imaging was analyzed. The Fourier telescope imaging system with different intensity and phase influence were studied in the three aspects of the theory, simulation and experiment. The results showed that the inte nsity and phase change of the time domain had a great influence on the Fourier telescope. At the same time, the scintillation and phase jitter effect on the Fourier telescope was successfully simulated by using numerical simulation method in the laboratory, and its influence on Fourier telescope was verified; a method for restraining the influence of intensity stationary variation on the Fourier telescope was presented.In the end, the feasibility of the application of flat-topped Beam in the Fourier telescope was analyzed. The energy attenuation effect of flat-topped Gaussian beam in the real atmosphere was analyzed by software simulation, and compared with that of Gaussian beam, with the conclusion of the largerirradiance concentration advantage of flat-topped beam. The application advantage of the Fourier telescope system with flattened Gaussian beam was discussed.In conclusion, this paper systematically studied the theory of beam optical turbulence propagation, the effects of atmospheric on the Fourier telescope and its corresponding suppression method. The establishment of flattened Gaussian optical propagation model had greatly reduced the theory difficulty of flat-topped Gaussian beam, and enriched and developed the theory of flattened Gaussian beam in turbulence. At the same time, the analysis of atmospheric turbulence effects on Fourier telescope and the suppression method research will provid support for the Fourier telescope system development, and help to further improve the resolution of Fourier telescope.