Abstract
We demonstrate strong coupling between two indium arsenide (InAs) quantum dots (QDs) and a photonic crystal cavity by using a magnetic field as a frequency tuning method. The magnetic field causes a red shift of an exciton spin state in one QD and a blue shift in the opposite exciton spin state of the second QD, enabling them to be simultaneously tuned to the same cavity resonance. This method can match the emission frequency of two QDs separated by detunings as large as 1.35 meV using a magnetic field of up to 7 T. By controlling the detuning between the two QDs we measure the vacuum Rabi splitting (VRS) both when the QDs are individually coupled to the cavity, as well as when they are coupled to the cavity simultaneously. In the latter case the oscillator strength of two QDs shows a collective behavior, resulting in enhancement of the VRS as compared to the individual cases. Experimental results are compared to theoretical calculations based on the solution to the full master equation and found to be in excellent agreement.
Highlights
Quantum dots (QDs) coupled to optical microcavities provide an ideal material system for studying cavity quantum electrodynamics
We investigate gallium arsenide (GaAs) photonic crystal cavity devices that are coupled to indium arsenide (InAs) QDs
In order to explain the experimental results, we model the QDs as two independent two-level systems interacting with a single cavity mode
Summary
Quantum dots (QDs) coupled to optical microcavities provide an ideal material system for studying cavity quantum electrodynamics (cQED). The study of multiple QD systems has remained technically challenging due to their wide spectral variations, making it extremely unlikely that two QDs will be resonant with the same cavity mode simultaneously To overcome this problem we require methods to individually tune multiple QDs to the same frequency. It has been shown that the DC Stark shift can be used to tune two QDs to the same frequency either by applying a separate electric bias to each QD using multi-layer diode structures [18], or by exploiting different voltage-dependent DC stark shifts between two QDs [19] The latter approach has already been used to tune two QDs to the same cavity mode in the strong coupling regime. Experimental results are compared to numerical simulation based on the solution to the full master equation and found to be in excellent agreement
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