Epsilon-near-zero thin films in a dual-functional system for thermal infrared camouflage and thermal management within the atmospheric window.

Abstract

Thermal infrared camouflage aims to reduce the detectability of a target using thermal imaging devices. Given the typically high thermal emissivity in everyday environments, the thermal emissivity of the background environment must be considered. The conventional low-emissivity strategy for thermal camouflage is only effective for targets at extremely high temperatures (>350 °C), making it unsuitable for applications near room-to-medium-high temperature range (<350 °C). In this study, we introduce metallic glass into infrared thermal camouflage technology, exploiting its adjustable emissivity to accommodate diverse infrared thermal camouflage scenarios. Moreover, we combined metallic glass with the Berreman mode of epsilon-near-zero (ENZ) thin films (SiO2, Al2O3, and TiO2) for the first time. In the long wave infrared (LWIR, 8-14 μm) regions, the small viewing angle exhibits the optical properties of metallic glasses, while the large viewing angle (above 45°) provides high thermal emissivity in transverse-magnetic (TM) polarization. A thermal management function was provided without affecting the thermal camouflage performance. The cooling power exhibited by ENZ thin films on metallic glass surpassed that of the conventional low-emissivity strategy for thermal camouflage by a factor of 1.79. Furthermore, the thermal images indicated over 97% similarity in thermal radiation between the target and background environments. We developed a dual-function system for infrared camouflage and thermal management within an identical wavelength region of the atmospheric window.