The Combination of the Azimuthally and Radially Polarized Beams: Helicity and Momentum Densities, Generation, and Optimal Chiral Light

Abstract

Herein, the optical properties of the azimuthally radially polarized beam (ARPB), a superposition of an azimuthally polarized beam and a radially polarized beam, which can be tuned to exhibit maximum chirality at a given energy density, are investigated. This condition is called “optimal chiral light” since it represents the maximum possible local chirality at a given energy density. The transverse fields of an ARPB dominate in the transverse plane but vanish on the beam axis, where the magnetic and electric fields are purely longitudinal, leading to an optical chirality density and an energy density that stem solely from the longitudinal field components on the beam axis, where the linear and angular momentum densities vanish. The ARPB does not have a phase variation around the beam axis and nonetheless exhibits a power flow around the beam axis that causes a longitudinal orbital angular momentum density. Herein, a concise notation for the ARPB is introduced and field quantities are provided, especially for the optimally chiral configuration. The ARPB shows promise for precise 1D chirality probing and enantioseparation of chiral particles along the beam axis, relying solely on its longitudinal electric and magnetic fields. Herein, a setup is provided to generate ARPBs with controlled chirality and orbital angular momentum.