The behavior of the light field near the beam waist has attracted considerable attention due to the studies of the light spin-orbit interaction: it’s manifestation as well as potential applications. Similarly, the light beam diffraction can reveal new light particularities. We have studied the far-field diffraction of a Gaussian beam by a half-plane edge placed near the beam waist. We have solved numerically the Helmholtz equation using the spectral method. We have found symmetric penetration of the light energy into the shadow region if we placed the half-plane edge exactly in the beam waist region. The symmetry gets broken down as the edge moves along the optical axis toward or away from the lens at a distance more than 0.01% of the focal length. Experimental verification has been obtained using a Gaussian beam focused by a lens of 4 cm focal length. The results can be used for precise determination of the beam waist position while investigating the effects of the light spin-orbit interaction in focused Gaussian beams.

中文翻译：

---

高斯光束在束腰附近的衍射

由于对光自旋轨道相互作用的研究，光束腰部附近的光场的行为引起了相当大的关注：它的表现以及潜在的应用。同样，光束衍射可以揭示新的光特性。我们已经研究了高斯光束通过束腰附近放置的半平面边缘的远场衍射。我们已经使用频谱方法对Helmholtz方程进行了数值求解。如果将半平面边缘恰好放置在光束腰部区域中，我们就会发现光能对称地穿透到阴影区域中。当边缘沿光轴移向或移离镜头的距离大于焦距的0.01％时，对称性将被破坏。使用高斯光束通过4 cm焦距镜头聚焦得到了实验验证。该结果可用于精确确定束腰位置，同时研究聚焦高斯束中光自旋-轨道相互作用的影响。