Continuous generation of delayed light

TL;DR

This paper demonstrates a method for continuously generating delayed light using Raman four-wave mixing, where the delay depends on system properties rather than optical depth, enabling background-free output and atomic coherence evolution monitoring.

Contribution

It introduces a novel continuous light generation technique based on atomic coherence, independent of optical depth, and uses spatial diffusion as an internal clock for atomic evolution.

Findings

Delay approaches atomic coherence lifetime at weak driving

Generated light is background free

Delay depends on system properties, not optical depth

Abstract

We use a Raman four-wave mixing process to read-out light from atomic coherence which is continuously written. The light is continuously generated after an effective delay, allowing the atomic coherence to evolve during the process. Contrary to slow-light delay, which depends on the medium optical depth, here the generation delay is determined solely by the intensive properties of the system, approaching the atomic coherence lifetime at the weak driving limit. The generated light is background free. We experimentally probe these properties utilizing spatial diffusion as an 'internal clock' for the atomic evolution time.