Temporal dynamics in the Bragg reflection of light by cold atoms: flash effect and superradiant decay

TL;DR

This paper investigates the temporal behavior of light in a cold atom lattice, revealing a flash effect and superradiant decay in Bragg reflection, advancing understanding for quantum-optical applications.

Contribution

It uncovers two novel effects in Bragg reflection—flash and superradiant decay—in cold atom systems, supported by classical photonic modeling.

Findings

Transient flash in reflected light when incident field is switched off

Superradiant decay rates up to several times the natural atomic decay rate

Qualitative agreement between numerical simulations and experimental observations

Abstract

We study the temporal dynamics of light interacting with a one-dimensional lattice of cold atoms. In such a system, a photonic band gap opens up, yielding an efficient Bragg reflection for an incident field incoming with the right angle and detuning. Here, we report two new effects appearing in the Bragg reflection. First, for some detunings, there is a ``flash'', i.e., a transient increase of the reflected intensity when the incident field is switched off. Second, the subsequent extinction of the reflected field is clearly superradiant, with decay rates up to height times the natural decay rate of the atomic excited state. Numerical simulations are in qualitative agreement with the observations, which can be explained by a classical photonic model. Our results are a step towards exploiting this photonic band gap in atomic systems for quantum-optical applications.