Generalized Lorenz–Mie theory of photonic wheels

Abstract

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.