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arXiv · 2606.22863

Free-Running Waveguide-Integrated Single-Photon Avalanche Detectors for Visible Light

Aswin Alexander·Anirudh R. Ramaseshan·Soe M. Thar·Thomas Y. L. Ang·Jing Zhou·Alexander Ling·Victor Leong
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Abstract

Waveguide-integrated single-photon avalanche detectors (SPADs) are essential components of integrated photonics platforms for scalable extreme-low-light applications without the use of cryogenics. Here, we demonstrate an integrated SPAD for visible light operating at room temperature in a free-running mode without gating. The device is based on a doped silicon diode end-fire-coupled to a silicon nitride (SiN) photonic integrated circuit (PIC). We investigate a range of lateral and vertical doping profile designs, and operate the devices with a simple current-mode passive quenching circuit. The optimal device is a laterally-doped p-i-n+ SPAD with a maximum photon detection efficiency (PDE) of 1.95 +/- 0.32% for input light at 685 nm wavelength, when reverse-biased at an excess of 1.5 V beyond the breakdown voltage of 15.0 V. We identify promising avenues for improving device performance, which would enable such integrated SPADs to be an attractive choice for cutting-edge integrated photonics solutions in quantum technologies, low-light imaging, and high-speed communications at visible wavelengths.

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Aswin Alexander, Anirudh R. Ramaseshan, Soe M. Thar, Thomas Y. L. Ang, Jing Zhou, Alexander Ling, Victor Leong. 2026-06-22. Free-Running Waveguide-Integrated Single-Photon Avalanche Detectors for Visible Light. https://arxiv.org/abs/2606.22863

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