Orbital-to-Spin Angular Momentum Conversion Employing Local Helicity

Abstract

Spin-orbit interactions in optics traditionally describe an influence of the polarization degree of freedom of light on its spatial properties. The most prominent example is the generation of a spin-dependent optical vortex upon focusing or scattering of a circularly polarized plane-wave by a nanoparticle, converting spin to orbital angular momentum of light. Here, we present a mechanism of conversion of orbital-to-spin angular momentum of light upon scattering of a linearly polarized vortex beam by a spherical silicon nanoparticle. We show that focused linearly polarized Laguerre-Gaussian beams of first order ($\ell =\pm 1$) exhibit an $\ell$-dependent spatial distribution of helicity density in the focal volume. By using a dipolar scatterer the helicity density can be manipulated locally, while influencing globally the spin and orbital angular momentum of the beam. Specifically, the scattered light can be purely circularly polarized with the handedness depending on the orbital angular momentum of the incident beam. We corroborate our findings with theoretical calculations and an experimental demonstration. Our work sheds new light on the global and local properties of helicity conservation laws in electromagnetism.

8 pages, 6 figures, 1 table

References in corpus (25)

• Spin-orbit interactions of light
• Optical spin-to-orbital angular momentum conversion in inhomogeneous anisotropic media
• Chiral Quantum Optics
• Chiral nanophotonic waveguide interface based on spin-orbit coupling of light
• Observation of the spin-based plasmonic effect in nanoscale structures
• Dual electromagnetism: Helicity, spin, momentum, and angular momentum
• Internal flows and energy circulation in light beams
• Angular Momenta and Spin-Orbit Interaction of Nonparaxial Light in Free Space
• Spin-to-orbital angular momentum conversion in focusing, scattering, and imaging systems
• Characterizing optical chirality
• Electromagnetic duality symmetry and helicity conservation for the macroscopic Maxwell's equations (previously "Experimental demonstration of electromagnetic duality symmetry breaking")
• Magnetoelectric Effects in Local Light-Matter Interactions
• Conservation of the spin and orbital angular momenta in electromagnetism
• On the experimental investigation of the electric and magnetic response of a single nano-structure
• Helicity and Angular Momentum. A Symmetry based framework for the study of Light-Matter Interactions
• Angular momentum-induced circular dichroism in non-chiral nanostructures
• Angular momentum of non-paraxial light beam: Dependence of orbital angular momentum on polarization
• The optical theorem for the conservation of the electromagnetic helicity: Its significance for molecular transfer and enantiomeric discrimination by dichroism
• Beaming of helical light from plasmonic vortices via adiabatically tapered nanotip
• Constructing a chiral dipolar mode in an achiral nanostructure
• Dual and anti-dual modes in dielectric spheres
• MIM Structure for optical vortex beam generator at nanoscale level
• Chiral optical fields: A unified formulation of helicity scattered from particles and dichroism enhancement
• Note on the helicity decomposition of spin and orbital optical currents
• Non-zero helicity extinction in light scattered from achiral (or chiral) small particles located at points of null incident helicity density

Cited by in corpus (16)

• Interaction of light carrying orbital angular momentum with a chiral dipolar scatterer
• Kerker Conditions Upon Lossless, Absorption, and Optical Gain Regimes
• Photoelectronic mapping of spin-orbit interaction of intense light fields
• Optical helicity of unpolarized light
• Kelvin's Chirality of Optical Beams
• Substrate-Induced Chirality in an Individual Nanostructure
• Unveiling dipolar spectral regimes of large dielectric Mie spheres from helicity conservation
• Momentum-space geometric structure of helical evanescent waves and its implications on near-field directionality
• Mimicking Chiral Light-Matter Interaction
• Sectoral Multipole Focused Beams
• Angular momentum conservation in counter-propagating vectorially structured light
• Focused linearly-polarized light scattering from a silver nanowire: Experimental characterization of optical spin-Hall effect
• Fundamentals and model of resonance helicity and energy transfer between two magnetoelectric chiral particles
• Conservation law for angular momentum based on optical field derivatives: Analysis of optical spin-orbit conversion
• Measures of Helicity and Chirality of Optical Vortex Beams
• A full characterization of the polarization of vector light beams