Waveguide Excitation and Spin Pumping of Chirally Coupled Quantum Dots

TL;DR

This paper demonstrates a remote excitation method for quantum dots in a photonic crystal waveguide that achieves high directionality and Purcell enhancement, advancing integrated quantum photonics.

Contribution

It introduces a remote p-shell excitation scheme that significantly improves directionality and decay rate enhancement of quantum dots in waveguides.

Findings

Achieved >95% directionality in quantum dot excitation and emission.

Demonstrated six-fold enhancement in quantum dot decay rate.

Established a new benchmark for waveguide quantum optics with combined Purcell and directionality improvements.

Abstract

We report on an integrated semiconductor chip where a single quantum dot (QD) is excited in-plane via a photonic-crystal waveguide through its nearest p-shell optical transition. The chirality of the waveguide mode is exploited to achieve both directional absorption and directional emission, resulting in a substantial enhancement in directional contrast, as measured for the Zeeman components of the waveguide-coupled QD. This remote excitation scheme enables high directionality (greater than or equal to 0.95) across approximately 56% of the waveguide area, with significant overlap with the Purcell-enhanced region, where the electric field intensity profile is near its peak. In contrast, local excitation methods using an out-of-plane excitation beam focused directly over the area of the QD achieve only approximately 25% overlap. This enhancement increases the likelihood of locating Purcell-enhanced QDs in regions that support high directionality, enabling the experimental demonstration of a six-fold enhancement in the decay rate of a QD with greater than 90% directionality. The remote p-shell excitation protocol establishes a new benchmark for waveguide quantum optics in terms of the combination of Purcell enhancement and high directionality, thereby paving the way for on-chip excitation of spin-based solid-state quantum technologies in regimes of high beta-factor.