Role of multi-level states on quantum-dot emission in photonic-crystal cavities

TL;DR

This paper demonstrates that the internal fine-structure of quantum dots significantly influences their emission in photonic-crystal cavities, challenging the common two-level approximation and affecting emission dynamics and spectra.

Contribution

It reveals that both fine-structure states of quantum dots couple to cavity modes due to polarization variations, altering emission behavior in current photonic-crystal systems.

Findings

Both fine-structure states couple significantly to cavity modes.

Emission spectra are modified in weak and strong coupling regimes.

Effects are significant for current state-of-the-art photonic-crystal cavities.

Abstract

Semiconductor quantum dots embedded in photonic-crystal nanostructures have been the subject of intense study. In this context, quantum dots are often considered to be simple two-level emitters, i.e., the complexities arising from the internal finestructure are neglected. We show that due to the intricate spatial variations of the electric field polarization found in photonic crystal, the two orthogonal finestructure states of quantum dots in general both couple significantly to a cavity mode, implying that the two-level description is not sufficient. As a consequence the emission dynamics and spectra, which are often recorded in experiments, are modified both in the weak- and strong-coupling regimes. The proposed effects are found to be significant for system parameters of current state-of-the-art photonic-crystal cavities.