Metalenses play an important role in optoelectronic integrated devices, given their advantages in miniaturization and integration. Due to its high aspect ratio subwavelength structure, fabricating metalenses requires a high-level dry etching technology. Consequently, structure deformation of the metalens will exist if the etching process of the material is not mature enough, which will impair the metalens’ performance. In this paper, a polarization-independent InP dielectric metalens is designed to focus the incident light from air into the substrate, which is used for monolithically integrating with the InGaAs/InP photodetector in the future. Subsequently, with the simulation method, we investigated the impact of the structure deformation on the metalens’ performance, which was found in our InP dry etching process development. We have found that the sidewall slope and aspect ratio-dependent etching effect greatly impaired the focusing efficiency because of the phase modulation deviation. To solve this problem, we proposed a manufacturing-tolerant design method, which effectively improved the performance of the device with structural deformation. Our work is instructive for developing metalenses and can accelerate their integration application.

The mid-wave single-crystal HgCdTe (211) films were successfully grown on GaAs (211) B substrates by molecular beam epitaxy (MBE). Microstructure and optical properties of the MBE growth HgCdTe films grown at different temperatures were characterized by X-ray diffraction, scanning transmission electron microscopy, Raman and photoluminescence. The effects of growth temperature on the crystal quality of HgCdTe/CdTe have been studied in detail. The HgCdTe film grown at the lower temperature of 151 °C has high crystal quality, the interface is flat and there are no micro twins. While the crystal quality of the HgCdTe grown at higher temperature of 155 °C is poor, and there are defects and micro twins at the HgCdTe/CdTe interface. The research results demonstrate that the growth temperature significantly affects the crystal quality and optical properties of HgCdTe films.

Metalenses, which can freely manipulate light fields, are regarded as highly promising optical components for enhancing the performance of photodetectors. In this letter, 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\mu $ m, is complemented by a $100\mu $ m $\times 100\mu $ m metalens that focuses incident photons into the photosensitive region. The focused beam size of the metalens is approximately $1.3\mu $ m (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.