On the orbit-induced spin density of tightly focused optical vortex beams: ellipticity and helicity

Abstract

It has recently been established that a linearly-polarized optical vortex possesses spin angular momentum density in the direction of propagation (longitudinal spin) under tight-focusing. The helicity of light has long been associated with longitudinal spin angular momentum. Here we show that the longitudinal spin density of linearly-polarized vortices is anomalous because it has no associated helicity. It was also recently determined that the polarization-independent helicity of tightly-focused optical vortices is associated with their transverse spin momentum density. The key finding of this work is the fact that, in general, longitudinal spin can not necessarily be associated with helicity, and transverse spin is in general not associated with a zero helicity, and such extraordinary behaviour manifests most clearly for optical vortices under non-paraxial conditions.

References in corpus (8)

• Characterizing optical chirality
• Measuring the Transverse Spin Density of Light
• Photoelectronic mapping of spin-orbit interaction of intense light fields
• Relevance of Longitudinal Fields of Paraxial Optical Vortices
• Optical helicity of unpolarized light
• Customized optical chirality of vortex structured light through state and degree of polarization control
• Spin/momentum properties of the paraxial optical beams
• Helicity, chirality and spin of optical fields without vector potentials

Cited by in corpus (2)

• Spin angular momentum and optical chirality of Poincaré vector vortex beams
• Generating optical angular momentum through wavefront curvature