Spontaneous emission decay and excitation in photonic time crystals

TL;DR

This paper investigates how photonic time crystals, with their time-periodic properties, significantly enhance spontaneous emission decay rates and enable a novel nonequilibrium excitation process, expanding control over light-matter interactions.

Contribution

It introduces the application of Floquet analysis to photonic time crystals, revealing enhanced decay rates and a new spontaneous excitation mechanism not observed in static structures.

Findings

Enhanced spontaneous emission decay rate at the momentum gap frequency.

Discovery of spontaneous emission excitation process in time-varying photonic environments.

Potential for dynamic control of light-matter interactions.

Abstract

Over the last few decades, the predominant strategies for controlling spontaneous emission have involved tailoring the spatial surroundings of quantum emitters or atoms to create resonant or spatially periodic photonic structures. However, the rise of time-varying photonics has prompted a reevaluation of spontaneous emission in dynamically changing environments, especially within photonic time crystals, where optical properties undergo time-periodic modulation. Here, we apply classical light-matter interaction theory together with Floquet analysis to reveal a substantial enhancement of the spontaneous emission decay rate at the momentum gap frequency in photonic time crystals. Moreover, our findings suggest that photonic time crystals enable a nonequilibrium light-matter interaction process: the spontaneous excitation of an atom from its ground state to an excited state, accompanied by the concurrent emission of a photon, referred to as spontaneous emission excitation.