40 × 40 Metalens Array for Improved Silicon Photomultiplier Performance

The photon detection efficiency (PDE) and timing performance of silicon photomultipliers (SiPMs) need to be improved for various applications, including time-of-flight positron emission tomography, light detection and ranging, and high-energy physics experiments. However, the irradiation of some incident photons to the low-photosensitivity areas of the SiPM negatively affects its PDE and timing performance. In this study, we developed a 40 × 40 metalens array to focus incident photons on the photosensitive area of the SiPM, thereby improving the PDE and timing performance. As a proof of concept, we experimentally investigated the effectiveness of this method. After characterizing the fabricated metalens, we found that the focused beam size is approximately 1 μm (full width at half-maximum) at the optimal focal plane. Furthermore, we demonstrated the effectiveness of the metalens in significantly improving the PDE (within a 5.8 σ confidence level) and timing performance (within a 3.0 σ confidence level). The results demonstrate the potential for using metalenses for versatile applications of SiPMs.