Optical vortices, beams with spiral wavefronts and screw phase dislocations, have been attracting increasing interest in various fields. Here, we theoretically propose and experimentally realize an easy approach to generating optical vortices. We leverage the inherent momentum-space topological vortex-like response of polarization (strong polarization anisotropy) around bound states in the continuum of two-dimensional periodic structures, for example photonic crystal slabs, to induce Pancharatnam–Berry phases and spin–orbit interaction in the beams. This new class of optical vortex generators operates in momentum space, meaning that the structure is almost homogeneous without a real-space centre. In principle, any even-order optical vortex that is a diffraction-resistant high-order quasi-Bessel beam can be achieved at any desired working wavelength. The proposed approach expands the application of bound states in the continuum and topological photonics.

光学涡旋，具有螺旋波阵面的光束和螺旋相错位，已经在各个领域引起了越来越多的兴趣。在这里，我们从理论上提出并通过实验实现了一种简便的方法来产生光学涡旋。我们利用二维周期结构（例如光子晶体平板）连续体中束缚态周围固有的动量-空间拓扑涡旋状极化（强极化各向异性）响应来诱发Pancharatnam–Berry相和自旋轨道相互作用。横梁。这种新型的光学涡旋发生器在动量空间中工作，这意味着结构几乎是均匀的，没有真实的空间中心。原则上，可以在任何所需的工作波长下实现任何抗衍射高阶准贝塞尔光束的偶数光学涡旋。所提出的方法扩展了束缚态在连续光子学和拓扑光子学中的应用。