Enhancing the photon-extraction efficiency of site-controlled quantum dots by deterministically fabricated microlenses

TL;DR

This paper presents a scalable method to enhance photon extraction from site-controlled quantum dots using deterministically fabricated microlenses, achieving high efficiency and low multi-photon probability for quantum photonic applications.

Contribution

It introduces a combined fabrication process of site-controlled quantum dots with microlenses, significantly improving photon extraction efficiency and suppression of multi-photon events.

Findings

Photon-extraction efficiency improved up to 21%

Multi-photon events suppressed with g^{(2)}(0) < 0.06

High-yield, high-precision fabrication process demonstrated

Abstract

We report on the realization of scalable single-photon sources (SPSs) based on single site-controlled quantum dots (SCQDs) and deterministically fabricated microlenses. The fabrication process comprises the buried-stressor growth technique complemented with low-temperature in-situ electron-beam lithography for the integration of SCQDs into microlens structures with high yield and high alignment accuracy. The microlens-approach leads to a broadband enhancement of the photon-extraction efficiency of up to (21 $\pm$ 2) $\%$ and a high suppression of multi-photon events with g$^{(2)}$($\tau$ = 0) $<$ 0.06 without background subtraction. The demonstrated combination of site-controlled growth of QDs and in-situ electron-beam lithography is relevant for arrays of efficient SPSs which can be applied in photonic quantum circuits and advanced quantum computation schemes.