Electromagnetically induced transparency resonances inverted in magnetic field

TL;DR

This study investigates how electromagnetically induced transparency resonances behave differently in two rubidium vapor cells under magnetic fields, revealing a reversal from dark to bright resonances likely due to atomic alignment effects.

Contribution

It demonstrates the inversion of EIT resonance signs in different vapor cell configurations and attributes this to atomic alignment influenced by magnetic and optical parameters.

Findings

EIT resonances are dark in nano-cell and bright in coated cell.

The resonance sign reversal is linked to atomic alignment effects.

Magnetic field and frequency configuration influence resonance behavior.

Abstract

The electromagnetically induced transparency (EIT) phenomenon has been investigated in a $\Lambda$-system of the $^{87}$Rb D$_1$ line in an external transverse magnetic field. Two spectroscopic cells having strongly different values of the relaxation rates $\gamma_{rel}$ are used: a Rb cell with antirelaxation coating ($L\sim$1 cm) and a Rb nanometric-thin cell (nano-cell) with thickness of the atomic vapor column $L$=795nm. For the EIT in the nano-cell, we have the usual EIT resonances characterized by a reduction in the absorption (i.e. dark resonance (DR)), whereas for the EIT in the Rb cell with an antirelaxation coating, the resonances demonstrate an increase in the absorption (i.e. bright resonances). We suppose that such unusual behavior of the EIT resonances (i.e. the reversal of the sign from DR to BR) is caused by the influence of alignment process. The influence of alignment strongly depends on the configuration of the coupling and probe frequencies as well as on the configuration of the magnetic field.