Refractive Index Enhancement with Vanishing Absorption in an Atomic Vapor

TL;DR

This paper demonstrates a method to enhance the refractive index of atomic vapor while keeping absorption near zero by using control lasers to induce and manipulate gain and absorption resonances in a two-photon Raman setup.

Contribution

It introduces a novel technique to achieve high refractive index with minimal absorption through interference of resonances controlled by laser parameters.

Findings

Refractive index is significantly enhanced without increased absorption.

Control laser parameters can tune the resonance features.

Interference between gain and absorption resonances enables index enhancement.

Abstract

We report a proof-of-principle experiment where the refractive index of an atomic vapor is enhanced while maintaining vanishing absorption of the beam. The key idea is to drive alkali atoms in a vapor with appropriate control lasers and induce a gain resonance and an absorption resonance for a probe beam in a two-photon Raman configuration. The strength and the position of these two resonances can be manipulated by changing the parameters of the control lasers. By using the interference between these two resonances, we obtain an enhanced refractive index without an increase in the absorption.