# Exploring coherence of individual excitons in InAs quantum dots embedded in natural photonic defects: influence of the excitation intensity

## TL;DR

This study uses four-wave mixing spectroscopy to analyze the coherence and dynamics of individual InAs quantum dots within natural photonic defects, revealing how excitation intensity influences their optical response and phonon interactions.

## Contribution

It demonstrates the use of FWM hyperspectral imaging combined with atomic force microscopy to study single QDs in natural defects and explores pulse area effects on Rabi rotations and phonon-induced dephasing.

## Key findings

- FWM signals originate from individual QDs in natural photonic defects.
- Rabi rotations are observable and depend on pulse area.
- Phonon-induced dephasing varies with excitation intensity.

## Abstract

The exact optical response of quantum few-level systems depends crucially on the exact choice of the incoming pulse areas. We use four-wave mixing (FWM) spectroscopy to infer the coherent response and dynamics of single InAs quantum dots (QDs) and study their pulse area dependence. By combining atomic force microscopy with FWM hyperspectral imaging, we show that the retrieved FWM signals originate from individual QDs enclosed in natural photonic defects. The optimized light-matter coupling in these defects allows us to perform our studies in a wide range of driving field amplitudes. When varying the pulse areas of the exciting laser pulses the so-called Rabi rotations can be resolved by the two-pulse FWM technique. We investigate these Rabi rotations within two- and three-level systems, both theoretically and experimentally, and explain their damping by the coupling to acoustic phonons. To highlight the importance of the pulse area influence, we show that the phonon-induced dephasing of QD excitons depends on the pulse intensity.