Imaging the transverse spin density of light via electromagnetically induced transparency

TL;DR

This paper introduces a real-time method to measure the transverse spin density of light using electromagnetically induced transparency in a multi-level atomic medium, simplifying existing complex techniques.

Contribution

It presents a novel scheme that spatially modulates medium susceptibility to directly image transverse spin density via Stokes parameter measurements.

Findings

Real-time measurement of transverse spin density achieved.

Spatial modulation of susceptibility correlates with transverse spin.

Method simplifies previous complex measurement techniques.

Abstract

When a light beam is strongly laterally confined, its field vector spins in a plane not perpendicular to the propagation direction, leading to the presence of transverse spin angular momentum, which plays a crucial role in the field of chiral quantum optics. The existing techniques to measure the transverse spin density require complex setups and sophisticated time-consuming procedures. Here, we propose a scheme to measure the transverse spin density of an optical field in real time using a multi-level atomic medium. The susceptibility of the medium is spatially modulated by the transverse spin via electromagnetically induced transparency. The distribution of the transverse spin is then extracted by measuring the distributions of the Stokes parameters of another collimated probe field.