Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics

TL;DR

This study investigates the spectral and dynamical properties of single quantum dots in cavity quantum electrodynamics, revealing discrepancies between spectral signatures and actual coupling strengths, and highlighting the importance of dynamical measurements.

Contribution

It provides a detailed comparison of spectral and dynamical measurements in quantum dot-cavity systems, revealing limitations of spectral signatures for assessing strong coupling.

Findings

Dissipative Jaynes-Cummings model describes micropillar cavity dynamics.

Spectral anti-crossing indicates strong coupling, but actual coupling is weaker.

Cavity feeding by other quantum dots affects observed Rabi splitting.

Abstract

We present detuning-dependent spectral and decay-rate measurements to study the difference between spectral and dynamical properties of single quantum dots embedded in micropillar and photonic-crystal cavities. For the micropillar cavity, the dynamics is well described by the dissipative Jaynes-Cummings model, while systematic deviations are observed for the emission spectra. The discrepancy for the spectra is attributed to coupling of other exciton lines to the cavity and interference of different propagation paths towards the detector of the fields emitted by the quantum dot. In contrast, quantitative information about the system can readily be extracted from the dynamical measurements. In the case of photonic crystal cavities we observe an anti crossing in the spectra when detuning a single quantum dot through resonance, which is the spectral signature of strong coupling. However, time-resolved measurements reveal that the actual coupling strength is significantly smaller than anticipated from the spectral measurements and that the quantum dot is rather weakly coupled to the cavity. We suggest that the observed Rabi splitting is due to cavity feeding by other quantum dots and/or multiexcition complexes giving rise to collective emission effects.