Plane light waves can carry angular momentum which is usually longitudinal (i.e. oriented along the axis of propagation). However, in confined (focused) light waves it can be oriented transversely (or perpendicular to the direction of propagation). Such electromagnetic fields therefore are called ‘photonic wheels’. We create photonic wheels with an aplanatic system and expand them into vector spherical harmonics. This decomposition is applied to create a generalized Lorenz–Mie theory of photonic wheels. We study the interaction of these beams with gold and silicon spheres and reveal an appearance of localized longitudinal angular momentum in the scattered field. Lastly, we employ the multiple scattering method and simulate a chiral cluster of nanoparticles in the focal plane of a photonic wheel.

平面光波可以携带角动量，该角动量通常是纵向的（即沿传播轴定向）。但是，在受限（聚焦）的光波中，它可以横向（或垂直于传播方向）定向。因此，这种电磁场称为“光子轮”。我们使用非平面系统创建光子轮，并将其扩展为矢量球谐函数。应用这种分解来创建广义的Lorenz-Mie光子轮理论。我们研究了这些光束与金和硅球的相互作用，并揭示了散射场中局部纵向角动量的出现。最后，我们采用多重散射方法，并在光子轮的焦平面上模拟了纳米粒子的手性簇。