Optical angular momentum derivation and evolution from vectorial field superposition

TL;DR

This paper presents a comprehensive vectorial field-based derivation of optical angular momentum, analyzing its components and evolution in arbitrary superposition states, including non-paraxial conditions, revealing intrinsic spin-orbit interactions.

Contribution

It introduces a vectorial formulation to derive and analyze all angular momentum components of optical fields in superposition states, highlighting spin-orbit shifts and transverse SAM effects.

Findings

Spin-orbit shift from longitudinal SAM to OAM in orthogonal superpositions

Local spin flow exhibits multiple helical trajectories

Significant spin-orbit and transverse SAM effects in non-paraxial regimes

Abstract

Optical intrinsic angular momentum can be regarded as derivation from spatial superposition of optical vector fields embodied by spinning or and spiraling the electric field vector. We employ vectorial formulation derivation to comprehensively study all angular momentum contents of optical vector fields in arbitrary superposition states, including the longitudinal and transverse, spin and orbital (SAM and OAM) components. As for the orthogonal superposition fields, there inherently exists spin-orbit shift from longitudinal SAM to OAM, and the whole local spin flow manifests local multiple fold helical trajectories. Especially, both the spin-orbit shift and transverse SAM could become considerable in the non-paraxial condition. Our studies here provide an explicit insight into the derivation and evolution, intrinsic correlations and salient features of various types of angular momentum components.