Monolithic Integration of InP Metalens With InGaAs/InP Single Photon Avalanche Diode

Metalenses, which can freely manipulate light fields, are regarded as highly promising optical components for enhancing the performance of photodetectors. In this paper, a novel InGaAs/InP single-photon avalanche diode (SPAD) with small active diameter and backside InP metalens is presented. The active area, with a diameter of 8 μm, is complemented by a 100 μm × 100 μm metalens that focuses incident photons into the photosensitive region. The focused beam size of the metalens is approximately 1.3 μm (full width at half-maximum) at the target focal plane. The novel SPAD with backside metalens achieves a maximum photon detection efficiency (PDE) of 15.9% at a wavelength of 1550 nm. Comparative experiments indicate that the integration of the metalens provides a 37% relative-increase in maximum PDE while maintaining a compact size. This work provides a new way for the realization of small-pixel, high-PDE InGaAs/InP SPAD arrays and supports the development of miniaturized, multi-dimensional photon detectors.