Anomalous exciton lifetime by an electromagnetic coupling of self-assembled quantum dots

TL;DR

This paper reports the experimental discovery of long-range electromagnetic coupling between self-assembled quantum dots, leading to a significant increase in exciton lifetime and tunable optical properties over distances exceeding 490 nm.

Contribution

It demonstrates a previously ignored electromagnetic coupling mechanism in quantum dots, extending local field effect theories to explain collective polarizability and lifetime enhancement.

Findings

12-fold increase in exciton lifetime observed

Coupling effective over distances >490 nm

Optical tuning of exciton lifetime achieved

Abstract

We report on the experimental observation of a hitherto ignored long-range electromagnetic coupling between self-assembled quantum dots. A 12 times enhancement of the quantum dot exciton lifetime is observed by means of time-resolved differential reflection spectroscopy. The enhancement is explained by utilizing and extending the local field effects as developed in \emph{Phys. Rev. B \textbf{64},125326 (2001)}. The electromagnetic coupling of the quantum dots results in a collective polarizability, and is observed as a suppression of the emission rate. Our results reveal that the coupling is established over a distance exceeding 490 nm. Moreover, the mutual coupling strength is optically tuned by varying the pump excitation density and enables us to optically tune the exciton lifetime.