Abstract
Future quantum technology relies crucially on building quantum networks with high fidelity. To achieve this challenging goal, it is of utmost importance to connect individual quantum systems such that their emitted single photons overlap with the highest possible degree of coherence. This requires perfect mode overlap of the emitted light from different emitters, which necessitates the use of single-mode fibres. Here, we present an advanced manufacturing approach to accomplish this task. We combined 3D printed complex micro-optics, such as hemispherical and Weierstrass solid immersion lenses, as well as total internal reflection solid immersion lenses, on top of individual indium arsenide quantum dots with 3D printed optics on single-mode fibres and compared their key features. We observed a systematic increase in the collection efficiency under variations of the lens geometry from roughly 2 for hemispheric solid immersion lenses up to a maximum of greater than 9 for the total internal reflection geometry. Furthermore, the temperature-induced stress was estimated for these particular lens dimensions and results to be approximately 5 meV. Interestingly, the use of solid immersion lenses further increased the localisation accuracy of the emitters to less than 1 nm when acquiring micro-photoluminescence maps. Furthermore, we show that the single-photon character of the source is preserved after device fabrication, reaching a $ g^{(2)} (0)$ value of approximately 0.19 under pulsed optical excitation. The printed lens device can be further joined with an optical fibre and permanently fixed.This integrated system can be cooled by dipping into liquid helium using a Stirling cryocooler or by a closed-cycle helium cryostat without the necessity for optical windows, as all access is through the integrated single-mode fibre. We identify the ideal optical designs and present experiments that demonstrate excellent high-rate single-photon emission.
Highlights
In recent years, various approaches have been followed for the realisation of solid-state single-photon emitters[1,2]
In conclusion, we successfully developed a reproducible method to enhance the collection efficiency in single quantum dots (QDs) spectroscopy using a combination of deterministic, optical low-temperature lithography with femtosecond 3D direct laser writing
The simplest geometry, namely h-solid immersion lenses (SILs), resulted in an intensity enhancement of approximately 2.1, which is in good agreement with the performed calculations
Summary
Various approaches have been followed for the realisation of solid-state single-photon emitters[1,2]. Many attempts have been made to increase the extraction efficiency of quantum dots, including photonic crystal structures[13], cavity quantum electrodynamics[5,6,14,15,16], plasmonic surface effects[17], and solid immersion lenses (SILs)[18,19,20,21,22]. Another crucial step in the development of practical quantum networks is the implementation of quantum repeater protocols, which enable long-distance quantum communication via optical fibre channels. An efficient on-chip single-mode fibre-coupled quantum light source is a key element in the realisation of a QD-based real-world quantum communication network
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