Hole coupling is a way to extract laser beams from an optical cavity through a hole on a cavity mirror. Hole coupling is often used in free electron laser oscillators and inherently causes a non-Gaussian beam profile at user stations, which are more than 10 m apart from the coupling hole. The laser beam extracted from a coupling hole has a bright central region (Airy disk) surrounded by a series of concentric rings (Airy pattern). The existence of an Airy pattern results in a non-Gaussian beam profile. It was demonstrated that the beam profile can be changed from a non-Gaussian to a nearly Gaussian distribution by removing the Airy pattern in the experiments and physical optics calculations.

中文翻译：

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空穴耦合自由电子激光振荡器复光束分布的起源研究

孔耦合是一种通过腔镜上的孔从光学腔中提取激光束的方法。空穴耦合常用于自由电子激光振荡器，并且在用户站内会产生非高斯光束轮廓，用户站距离耦合孔超过 10 m。从耦合孔中提取的激光束有一个明亮的中心区域（艾里斑），周围环绕着一系列同心环（艾里斑）。艾里图案的存在导致非高斯光束轮廓。结果表明，通过去除实验和物理光学计算中的艾里图案，光束轮廓可以从非高斯分布变为接近高斯分布。