Azimuthal modulation of electromagnetically induced transparency using structured light

TL;DR

This paper proposes a method to detect structured light by measuring azimuthal-dependent absorption in a five-level atom system, revealing spatially varying electromagnetically induced transparency linked to the light's orbital angular momentum.

Contribution

It introduces a novel detection scheme using a five-level CTL atom-light setup that exploits the closed-loop structure to sense the azimuthal and OAM properties of structured light.

Findings

Absorption depends on azimuthal angle and OAM of control vortex beams.

The scheme enables spatially structured transparency detection.

It surpasses simple lambda or tripod schemes by utilizing a closed-loop configuration.

Abstract

Recently a scheme has been proposed for detection of the structured light by measuring the transmission of a vortex beam through a cloud of cold rubidium atoms with energy levels of the $\Lambda$-type configuration {[}N. Radwell et al., Phys. Rev. Lett. 114, 123603 (2015){]}. This enables observation of regions of spatially dependent electromagnetically induced transparency (EIT). Here we suggest another scenario for detection of the structured light by measuring the absorption profile of a weak nonvortex probe beam in a highly resonant five-level combined tripod and $\Lambda$ (CTL) atom-light coupling setup. We demonstrate that due to the closed-loop structure of CTL scheme, the absorption of the probe beam depends on the azimuthal angle and orbital angular momentum (OAM) of the control vortex beams. This feature is missing in simple $\Lambda$ or tripod schemes, as there is no loop in such atom-light couplings. One can identify different regions of spatially structured transparency through measuring the absorption of probe field under different configurations of structured control light.