# Influence of the asymmetric excited state decay on coherent population trapping: atom $\times$ quantum dot

## TL;DR

This study compares the optical properties of atomic systems and quantum dot molecules under electromagnetically induced transparency and coherent population trapping, highlighting how asymmetric decay rates affect their nonlinear responses and cavity interactions.

## Contribution

It reveals the impact of asymmetric excited state decay rates on the optical properties of QDMs versus atoms in CPT regimes, and demonstrates improved dark state resonance narrowing in QDM-cavity systems.

## Key findings

- In the EIT regime, atomic and QDM systems exhibit identical optical properties.
- In the CPT regime, decay rate differences cause significant discrepancies in nonlinear susceptibilities.
- QDM-cavity systems achieve narrower dark state resonances compared to atom-cavity systems.

## Abstract

Electromagnetically induced transparency (EIT) is an optical phenomenon which allows a drastic modification of the optical properties of an atomic system by applying a control field. It has been largely studied in the last decades and nowadays we can find a huge number of experimental and theoretical related studies. Recently a similar phenomenon was also shown in quantum dot molecules (QDM) , where the control field is replaced by the tunneling rate between quantum dots. Our results show that in the EIT regime, the optical properties of QDM and the atomic system are identical. However, here we show that in the strong probe field regime, i.e., "coherent population trapping" (CPT) regime, it appears a strong discrepancy on the optical properties of both systems. We show that the origin of such difference relies on the different decay rates of the excited state of the two systems, implying in a strong difference on their higher order nonlinear susceptibilities. Finally, we investigate the optical response of atom/QDM strongly coupled to a cavity mode. In particular, the QDM-cavity system has the advantage of allowing a better narrowing of the width of the dark state resonance in the CPT regime when compared with atom-cavity system.