Directional scattering from particles under evanescent wave illumination: the role of reactive power

Abstract

Study of photonic spin-orbital interactions, which involves control of the propagation and spatial distributions of light with the polarization of electromagnetic fields, is not only important at the fundamental level but also has significant implications for functional photonic applications that require active tuning of directional light propagation. Many of the experimental demonstrations have been attributed to the spin-momentum locking characteristic of evanescent waves. In this letter, we show another property of evanescent waves: the polarization dependent direction of the imaginary part of the Poynting vector, i.e. reactive power. Based on this property, we propose a simple and robust way to tune the directional far-field scattering from nanoparticles near a surface under evanescent wave illumination by controlling linear polarization and direction of the incident light.

Electromagnetic dynamical characteristics of a surface plasmon-polariton

“…(30) with a certain sort of electric current can only be made on the base of a specific model relating the nature of the charge carries in the medium 2. E.g., a mechanical momentum of the common motion of oppositely charged and equally massive quasiparticles means no electric current (instead of the surface current (38)) and, correspondingly, no magnetization.…”

“…(4) with interchanged permittivities and permeabilities) but its interpretation is not as direct as that given by Eq. (38). We cannot associate expression (49) with the surface electric current and/or magnetization without additional knowledge on the medium 2 structure which, in this case, is a complex metamaterial with the dispersive permeability  2 () < 0.…”

“…For completeness, we additionally present the expressions for the imaginary Poynting momentum (reactive momentum [28]) that also plays an important role in the light-matter interaction [38], in particular, it is responsible for the noticeable ponderomotive action on material particles [8,39,40]. Like the energy flow density (16), it is an essentially kinetic property (the physical meaning of its spin-orbital decomposition is doubtful) and shows no explicit dependence on dispersion (more exactly, its known physical manifestations are not related to the dispersion).…”

“…This current, strictly localized at the surface of the conductive medium, can be considered as an analog of the Ampere current explaining the magnetization of permanent magnets [42]. In particular, due to the Maxwell's boundary condition [28,29,42], the surface current (38) means that the magnetic field discontinuity occurs at the interface…”

“…Evidently, the surface current (38) should be a part of a closed circuit that can be completed by the equivalent oppositely directed current density in the medium 2 volume, magn j , related to the volume magnetization…”