One-dimension hybrid Ge/ZnS photonic crystal film tailored for thermal-stable laser-infrared compatible camouflage

Abstract

A polarization-independent broadband infrared wavelength selective emitter (IWSE) based on hybrid photonic crystal architectures is proposed and demonstrated. The salient feature is that it composes of alternating Ge/ZnS layers configuration with specially crafted gradient thickness, which renders it low average emissivity of less than 0.15 in two atmospheric windows of 3–5 μm and 8–14 μm, high average emissivity of more than 0.6 in non-atmospheric window of 5–8 μm, and strong narrowband absorption at 10.6 μm. Since the accumulated thermal energy can be effectively dissipated, it is very suitable for the application of effective thermal-stable laser-infrared compatible camouflage. The comprehensive dependence of broadband selective emission properties on structural parameters, polarization and incident angle of the incoming excitation are studied. The underlying physical mechanisms are explored and the basic guidelines for designing IWSE are achieved. It is found that the doped impurity layers lead to an absorption hybridization effect in the photonic crystal heterojunction and that the narrowband absorption at 10.6 μm essentially originates from the Fabry-Perot resonance localized within the doped layers unit and exists as an impurity state in photonic crystal bandgap. The regulation of the absorption hybridization effect is detailedly investigated. Furthermore, we reexamine the principle difference between the infrared and laser camouflage and propose a generalized method for evaluating the laser-infrared compatible camouflage performance of IWSE. The proof-of-principle IWSE is fabricated, and the measured infrared emission property is in agreement with the simulations. High temperature durability of the proposed IWSE was experimentally ensured up to more than 400 °C, which shows that the IWSE scheme can be expected to have further practical application in territory of high performance laser-infrared compatible camouflage under variable temperature environments.