Influence of random fluctuation of field phase on contrast ratio of far field of coherent combined laser beams

In order to analyze the influence of phase random fluctuation on the far field of coherent combined beams,the theoretical ways of Fourier optics method and ergodic hypothesis were employed to study the fringe contrast.The analytic expression of the fringe contrast ratio of coherent combined beam was deduced and the influence of random fluctuation of field phases on the contrast ratio of the far field pattern was numerically simulated successfully.Results show that with the quantity η increasing,the contrast ratio of coherent combined beams increase accordingly.The fringe contrast ratio of the far field pattern decreases when the root mean square of phase δφ enhances.For a fixed standard deviation of the phase's fluctuation and the quantity η,the larger the number of the constituent fields is,the bigger the fringe contrast ratio is.These results are useful for understanding of the characteristic of coherent combined beams.