Photonic Spin Hall Effect of Nanoparticles: Fundamentals, Advances, and Applications

The net angular momentum of light remains conserved during propagation. This conservation leads to a spin transport which becomes evident when light encounters a refractive index gradient, i.e., when it is reflected, refracted, or scattered. The phenomenon is so-called as the spin-orbit interaction (SOI) of light has paved the way to manipulate the light-matter interaction at the nanoscale and has remained the core of many recent studies. Particularly, the photonic spin Hall effect (PSHE) which is the microscopic spin splitting into circular polarization has given rise to novel applications, for example, precision metrology. The PSHE is well explored at planar interfaces, however much less attention is given to it when the optical potential gradient is of higher dimensionality, i.e., for nanoparticles. In this review, the theoretical description of the PSHE as well as the SOI in the scattering of light from nanoparticles are covered. Recent advances and trends in the PSHE in nanoparticles are reviewed. The review is concluded with suggestions for some novel directions in the field of PSHE of nanoparticles.