Opt Express. 2023 Mar 13;31(6):9904-9914. doi: 10.1364/OE.484306.
We theoretically investigate the combining efficiency and combined beam quality degradation induced by beam array misalignment in a coherent combining system based on diffractive optical elements. Theoretical model is established based on the Fresnel diffraction. We consider pointing aberration, positioning error and beam size deviation in array emitters as typical misalignments, and discuss their influences on beam combining by this model. The statistical analysis results and the accurate fitting curves of the degradation have been given based on the repetitive simulations with normal distributed random misalignments. According to the results, the combining efficiency is affected greatly by the pointing aberration and position error of the laser array, while the combined beam quality is just affected by the pointing aberration generally. Based on calculation with a series of typical parameters, the standard deviations of the laser array's pointing aberration and position error are required to less than 15μrad and 1μm respectively to maintain an excellent combining efficiency. If we only concentrate on the beam quality, the pointing aberration need to be less than 70μrad.
我们从理论上研究了基于衍射光学元件的相干合成系统中光束阵列失准引起的组合效率和组合光束质量下降。理论模型是基于菲涅耳衍射建立的。我们将点扩散函数、定位误差和阵列发射器中的光束尺寸偏差视为典型的失准，并通过该模型讨论它们对光束合成的影响。基于正态分布随机失准的重复模拟，给出了退化的统计分析结果和精确拟合曲线。根据结果，激光阵列的点扩散函数和位置误差对组合效率有很大影响，而组合光束质量一般仅受点扩散函数影响。通过一系列典型参数的计算，要求激光阵列的点扩散函数和位置误差的标准偏差分别小于 15μrad 和 1μm，以保持优异的组合效率。如果我们只关注光束质量，那么点扩散函数需要小于 70μrad。
