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arXiv · 2603.24070

In-Line Fiber-Integrated Photon-Pair Generation from van der Waals Crystals

Mayank Joshi·Tanumoy Pramanik·Mengting Jiang·Yu Xing·Zhaogang Dong·Yuerui Lu·Jie Zhao·Ping Koy Lam·Syed M. Assad·Xuezhi Ma·In Cheol Seo·Young-Wook Cho
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Abstract

Miniaturized quantum light sources that operate directly in optical fibers are an attractive platform for optical quantum technologies. However, most miniaturized spontaneous parametric down- conversion (SPDC) sources still rely on objective-lens-based free-space pumping and collection, which limits compactness, robustness, and direct compatibility with fiber-based systems. Here we demonstrate a lens-free in-line SPDC photon-pair source by integrating a van der Waals NbOI2 flake directly onto the end facet of an optical fiber. In this configuration, the generated photon- pairs are efficiently collected into optical fibers, eliminating the need for bulk free-space collection optics. Despite the limited numerical aperture of the single-mode fiber, efficient photon-pair collection with high purity, characterized by a coincidence-to-accidental ratio of up to ~4600, is achieved in an ultracompact configuration. These results establish van der Waals ferroelectric materials as a promising platform for fiber-integrated quantum light sources and provide a pathway toward compact, alignment-free quantum photonic devices.

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Mayank Joshi, Tanumoy Pramanik, Mengting Jiang, Yu Xing, Zhaogang Dong, Yuerui Lu, Jie Zhao, Ping Koy Lam, Syed M. Assad, Xuezhi Ma, In Cheol Seo, Young-Wook Cho. 2026-03-25. In-Line Fiber-Integrated Photon-Pair Generation from van der Waals Crystals. https://arxiv.org/abs/2603.24070

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