基于惠更斯-菲涅耳衍射理论进行数值计算,发现柱面望远镜整形系统的柱面镜旋转失调不仅会导致平行光束远场焦斑旋转倾斜,还会导致其在倾斜方向上出现拉长、离焦现象,该像差来源于柱面镜旋转导致的像散与离焦的叠加,上述结果说明远场焦斑的离焦也可以出现在旋转失调的柱面镜整形系统中。此外,定量给出包含激光中心波长、整形光束尺寸、柱面镜间距、放大率的归一化相位系数与远场焦斑形态的相关关系,该系数可以用于评判柱面整形系统对柱面镜旋转失调的敏感度。最后搭建了相应的实验装置进行验证,实验结果与计算结果较好地吻合。

In numerical and experimental analyses, we studied the effect of misaligning the cylindrical mirror rotation in shaping system on the far-field spot and beam quality of the laser during beam shaping based on Huygens--Fresnel diffraction theory. Increasing the rotation angle not only rotated and tilted the far-field spot of the shaping beam, but also elongated and defocused the spot. This aberration derives from the superposition of astigmatism and defocusing caused by rotating the cylindrical mirror. The results show that misaligned rotation also defocuses the shaping system with cylindrical mirror. We then quantitatively analyzed the correlation among the normalized phase coefficient and focal spot, in which the normalized phase coefficient is related with the center wavelength of the laser, size of the shaping beam, distance of the cylindrical mirrors and magnification factor. From the correlation coefficient, we can evaluate the sensitivity of the shaping system to the cylinder-mirror rotation disorder. Finally, we verified our calculated results using a corresponding experimental device. The experimental results agreed well with the calculated results.