Interacting double dark resonances in a hot atomic vapor of helium

TL;DR

This paper investigates how two types of dark resonances interact in a hot helium vapor, revealing merging and destructive interference effects that influence transparency and absorption.

Contribution

It provides both experimental and theoretical analysis of dark resonance interactions in helium, highlighting new interference phenomena under different polarization configurations.

Findings

Dark resonances merge into a single EIT peak with increased power.

Destructive interference causes an extra absorption peak at line center.

Experimental and theoretical results agree on resonance behavior.

Abstract

We experimentally and theoretically study two different tripod configurations using metastable helium ($^4$He*), with the probe field polarization perpendicular and parallel to the quantization axis, defined by an applied weak magnetic field. In the first case, the two dark resonances interact incoherently and merge together into a single EIT peak with increasing coupling power. In the second case, we observe destructive interference between the two dark resonances inducing an extra absorption peak at the line center.