Group velocity control in the ultraviolet domain via interacting dark-state resonances

TL;DR

This paper demonstrates how to control the group velocity of ultraviolet light in a mercury atomic system using interacting dark-state resonances and incoherent pumping, enabling switchable superluminal and subluminal propagation.

Contribution

It introduces a method to manipulate light speed in the ultraviolet domain through dark-state resonances combined with incoherent pumping in a four-level atomic system.

Findings

High-resolution spectral peaks due to dark resonances in mercury atoms.

Achieving superluminal light propagation with absorption.

Controlling group velocity to be subluminal or negative without absorption.

Abstract

The propagation of a weak probe field in a laser-driven four-level atomic system is investigated. We choose mercury as our model system, where the probe transition is in the ultraviolet region. A high-resolution peak appears in the optical spectra due to the presence of interacting dark resonances. We show that this narrow peak leads to superluminal light propagation with strong absorption, and thus by itself is only of limited interest. But if in addition a weak incoherent pump field is applied to the probe transition, then the peak structure can be changed such that both sub- and superluminal light propagation or a negative group velocity can be achieved without absorption, controlled by the incoherent pumping strength.