Interference between single photons is key for many quantum optics experiments and applications in quantum technologies, such as quantum communication or computation. It is advantageous to operate the systems at telecommunication wavelengths and to integrate the setups for these applications in order to improve stability, compactness and scalability. A new promising material platform for integrated quantum optics is lithium niobate on insulator (LNOI). Here, we realise Hong-Ou-Mandel (HOM) interference between telecom photons from an engineered parametric down-conversion source in an LNOI directional coupler. The coupler has been designed and fabricated in house and provides close to perfect balanced beam splitting. We obtain a raw HOM visibility of (93.5+/-0.7)%, limited mainly by the source performance and in good agreement with off-chip measurements. This lays the foundation for more sophisticated quantum experiments in LNOI
@article{arxiv.2212.12261,
title = {Demonstration of Hong-Ou-Mandel interference in an LNOI directional coupler},
author = {Silia Babel and Laura Bollmers and Marcello Massaro and Kai Hong Luo and Michael Stefszky and Federico Pegoraro and Philip Held and Harald Herrmann and Christof Eigner and Benjamin Brecht and Laura Padberg and Christine Silberhorn},
journal= {arXiv preprint arXiv:2212.12261},
year = {2023}
}