Group velocity control in a four level system through interacting dark resonances

TL;DR

This paper explores how interacting dark resonances in a four-level atomic system can be used to control light's group velocity, enabling transitions between subluminal and superluminal propagation through incoherent pumping.

Contribution

It demonstrates the manipulation of dispersion and absorption properties via dark resonances and incoherent pumping in a four-level system, revealing new control over light propagation speeds.

Findings

Two narrow peaks in spectra due to dark resonances

Superluminal light propagation with strong absorption

Transition to gain deeps with incoherent pumping

Abstract

We investigate dispersion and absorption properties of a weak probe field in a four level atomic system through interacting dark resonances. We show that two narrow peaks appears in the optical spectra due to the presence of interacting dark resonances. This two narrow peaks leads to the superluminal light propagation with strong absorption. However, if a weak incoherent pump field is exerted to the probe transition, then the peaks structures can be changed such that two absorption peaks transformed to two gain deeps. We Show that both subluminal and superluminal light propagation occur in this system, where controlled by the incoherent pumping strength.