M2-factor, mode decomposition and beam combining of partially coherent flat-topped beams
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摘要: 推导出以模式间相互独立的厄米高斯光束为基底的部分相干平顶光束的模系数和M2因子的解析式,对部分相干平顶光束的模分解及合成进行了研究.研究结果表明,随着光束阶数M及表征光束相干性的参数w0/ν0的增加,基模的份额减小,M2因子增大.采用模式间相互独立的厄米高斯光束叠加的方法合成部分相干平顶光束的光强矩形分布与光束M2因子二者无法同时兼顾,即若要求空间分布非常接近矩形,则光束的M2因子较大,若要求光束的M2因子较小,则只能降低对光强矩形分布的要求.在实际工作中,可以通过选择恰当的基底基模高斯光束的束腰尺寸以及控制各模式的光功率,由模式间相互独立的厄米高斯光束合成部分相干平顶光束.Abstract: The analytical expressions for the mode coefficients and M2-factor of partially coherent flat-topped beams which can be combined by independent Hermite-Gaussian beams have been derived.The mode decomposition and mode composition of partially coherent flat-topped beams have been analyzed.The basis Gaussian mode decreases and the M2-factor increases with the beam order M and the parameter w0/ν0 increasing.The M2-factor and the rectangular shape of the flat-topped beams combined by the independent Hermite-Gaussian beams can not be obtained at the same time.If an approach rectangular shape of the intensity distribution of partially coherent flat-topped beams is desired,the M2-factor must be large.If the small value of M2-factor is required,the strictly rectangular shape of the intensity distribution can not be obtained.In many practical cases,the partially coherent flat-topped beams can be combined by the superposition of the independent Hermite-Gaussian beams with the proper choice of the beam waist and the power content.
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