Coherent control of group index and magneto-optical anisotropy in a multilevel atomic vapor

TL;DR

This paper demonstrates the control of group index and magneto-optical anisotropy in a heated potassium vapor using electromagnetically induced transparency, with detailed measurements and a comprehensive theoretical model.

Contribution

It introduces a simple experimental setup for EIT in potassium vapor and provides a detailed analytical model for the observed phenomena.

Findings

Deeply sub-natural linewidth transparency windows achieved.

Magneto-optical anisotropy varies with polarization configuration.

Theoretical model accurately reproduces experimental spectra.

Abstract

We study electromagnetically induced transparency (EIT) in a heated potassium vapor cell, using a simple optical setup with a single free-running diode laser and an acousto-optic modulator. Despite the fact that the Doppler width is comparable to the ground state hyperfine splitting, transparency windows with deeply sub-natural line widths and large group indices are obtained. A longitudinal magnetic field is used to split the EIT feature and induce magnetooptical anisotropy. Using the beat note between co-propagating coupling and probe beams, we perform a heterodyne measurement of the circular dichroism (and therefore birefringence) of the EIT medium. The observed spectra reveal that lin-par-lin polarizations lead to greater anisotropy than lin-perp-lin. A simplified analytical model encompassing sixteen Zeeman states and eighteen \Lamda\ subsytems reproduces the experimental observations.