GaAs Quantum Dot in a Parabolic Microcavity Tuned to 87Rb D1.

Thomas Lettner,Samuel Gyger,Eva Schöll,Katharina D Zeuner,Klaus D Jöns,Armando Rastelli,Val Zwiller,Huiying Huang,Selim Scharmer,Saimon Filipe Covre Da Silva,Lucas Schweickert

doi:10.1021/acsphotonics.9b01243

Thomas Lettner, Samuel Gyger + Show 9 more

Open Access

https://doi.org/10.1021/acsphotonics.9b01243

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Abstract

We develop a structure to efficiently extract photons emitted by a GaAs quantum dot tuned to rubidium. For this, we employ a broadband microcavity with a curved gold backside mirror that we fabricate by a combination of photoresist reflow, dry reactive ion etching in an inductively coupled plasma, and selective wet chemical etching. Precise reflow and etching control allows us to achieve a parabolic backside mirror with a short focal distance of 265 nm. The fabricated structures yield a predicted (measured) collection efficiency of 63% (12%), an improvement by more than 1 order of magnitude compared to unprocessed samples. We then integrate our quantum dot parabolic microcavities onto a piezoelectric substrate capable of inducing a large in-plane biaxial strain. With this approach, we tune the emission wavelength by 0.5 nm/kV, in a dynamic, reversible, and linear way, to the rubidium D1 line (795 nm).

Highlights

Quantum photonics is making significant progress due to the development of novel single-photon sources based on semiconductor quantum dots providing single and entangled photon generation on demand, with high purity, near-unity indistinguishability, and tunable emission energy.[1,2]
Both spectra are very typical for Al droplet gallium arsenide (GaAs) quantum dots, with an isolated exciton (XQD1) line at lower wavelength and an ensemble of lines at higher wavelengths
We further extract from above-band pulsed excitation measurements a photon collection efficiency of 12% for the neutral exciton emission of a bright quantum dot in a parabolic microcavity, which is comparable to the values demonstrated for the optical horn structure.[35]

Summary

Introduction

Quantum photonics is making significant progress due to the development of novel single-photon sources based on semiconductor quantum dots providing single and entangled photon generation on demand, with high purity, near-unity indistinguishability, and tunable emission energy.[1,2] They are currently of high relevance in quantum information processing applications,[3] such as quantum networks, quantum simulation, and quantum cryptography. Piezoelectric actuators have emerged as a powerful method for tuning quantum dot properties,[26] where the induced strain allows to reversibly adjust the emission wavelength of quantum dots in microcavities[27−30] as well as their fine structure splitting.[31−34] the desired device combining broadband microcavities, Gaussian emission profile for fiber coupling, and tuning to generate on-demand wavelength-tunable single photons has not been realized so far.

Results

Conclusion