A proposal to measure Belinfante’s curl of the spin optical force based on the Kerker conditions

Abstract

The linear momentum of electromagnetic radiation is proportional to the Poynting vector. However, when light interacts with a dipole, the radiation pressure generated is no longer proportional to the Poynting vector: the so-called Belinfante’s momentum or equivalently, the curl of the spin density of the light field, must be considered. In this paper, we propose an optical configuration, based on two evanescent counter-propagating waves, perpendicularly polarized, capable of detecting Belinfante’s mechanical action. The two beams interact with a high-refractive-index particle like silicon. The direction of the radiation pressure exerted on the particle, proportional only to the curl of the spin density, depends on the electric and magnetic response of the particle and changes sign at the radiation wavelengths corresponding with the Kerker conditions.