Aspheric lens design proposal for near-perfect mode-matching of a broadband quantum dot micropillar to a single-mode fiber

Quantum dots in micropillars are one of the most promising options for a bright, deterministic single photon source. While highly efficient devices (>95%) have been designed, there remains a significant bottleneck that impacts the overall system efficiency: the large numerical aperture of the output mode. This leads to inefficient coupling of emitted photons into single-mode fiber (SMF), thus limiting practical integration into quantum computing and communication architectures. We show that with the addition of a well designed aspheric SiO₂ microlens we can decrease the mode-matching losses to a SMF from 83.1% to <0.1(0.1)%. This can result in a single photon source design with 96.4(0.1)% end-to-end efficiency, paving the way for scalable photonic quantum technologies.