Spin-orbit interaction of light induced by transverse spin angular momentum engineering

Abstract

The investigations on optical angular momenta and their interactions have broadened our knowledge of light’s behavior at sub-wavelength scales. Recent studies further unveil the extraordinary characteristics of transverse spin angular momentum in confined light fields and orbital angular momentum in optical vortices. Here we demonstrate a direct interaction between these two intrinsic quantities of light. By engineering the transverse spin in the evanescent wave of a whispering-gallery-mode-based optical vortex emitter, a spin-orbit interaction is observed in generated vortex beams. Inversely, this unconventional spin-orbit interplay further gives rise to an enhanced spin-direction locking effect in which waveguide modes are unidirectionally excited, with the directionality jointly controlled by the spin and orbital angular momenta states of light. The identification of this previously unknown pathway between the polarization and spatial degrees of freedom of light enriches the spin-orbit interaction phenomena, and can enable various functionalities in applications such as communications and quantum information processing.

Geometrical phase and Hall effect associated with the transverse spin of light

“…Most importantly, the transverse-spin-dependent geometrical phase underpins a novel class of SOI effects of light. Actually, it has already been demonstrated experimentally that the transverse-spin-dependent geometrical phase results in the interaction between the intrinsic orbital AM and the transverse spin of light [24].…”

Mode Division Multiplexing Based on Ring Core Optical Fibers

“…A common feature of above circularly distributed waveguide OAM emitter is that they emit vector modes that are either predominantly tangential or radial polarized, which is not matched to RCF's circularly polarized OAM modes. Recently the authors addressed this problem by engineering the so-called 'transverse spin' in the evanescent wave region of silicon nitride micro-ring waveguides, achieving arbitrary control over the emitted OAM mode SoP [64]. A silicon PIC-based circularpolarized OAM MUX/DEMUX targeting direct chip-to-fibre coupling was also proposed recently [65].…”

Orbital angular momentum vector modes (de)multiplexer based on multimode micro-ring

“…These results confirm that the device is capable of multiplexing four vector OAM modes at two wavelengths. It is noted that scalar OAM modes (with circular polarization) can also be generated from a ring resonator with optimized waveguide [28]. The mode purities of OAM modes play crucial roles in OAM multiplexing applications.…”