Metalens arrays for high-operating-temperature HgCdTe MWIR detectors: design and modelling

We present the design and modelling of metalens arrays integrated with mid-wave infrared (MWIR, 3–5 µm) HgCdTe (MCT) focal plane arrays (FPAs). Silicon and germanium micro-metalens structures were modelled using rigorous coupled-wave analysis (RCWA). By concentrating incident light into reduced junction areas, microlenses suppress dark current and enable high-operating-temperature (HOT) detectors. Two application cases are considered: (i) high-resolution imaging, quantified by the noise-equivalent temperature difference (NETD) as a function of temperature, and (ii) subpixel bushfire detection, assessed via radiometric contrast as a function of source distance. Simulations indicate that microlens-enhanced FPAs maintain NETD ≤ 35 mK at temperatures compatible with thermoelectric coolers (TECs), eliminating the need for bulky cryogenic cooling systems. For bushfire detection, a 5 × 5 m² hotspot at 1000 K remains detectable beyond 9 km with microlenses, compared to only ~1.5 km without microlenses at elevated temperatures. These results suggest the potential of microlens-integrated FPAs to deliver compact, low-SWaP-C (Size, Weight, Power consumption, and Cost) MWIR systems for high-performance imaging and scalable civilian monitoring applications.