Spectrally selective thermal emission is in high demand for thermophotovoltaics, radiative cooling, and infrared sensing applications. Spectral control of the emissivity is historically achieved by choosing the material with suitable infrared properties. The recent advancements in nanofabrication techniques that lead to enhanced light–matter interactions enable optical properties like infrared emissivity that are not naturally available. In this study, thermal emitters based on nanometer‐thick dielectrics on field‐enhancement surfaces as optical security features are proposed. Such a function is achieved by generating patterns by ultrathin dielectrics that are transparent in the visible and exhibit strong infrared absorption in the spectral range of thermal cameras. The invisible patterns are then revealed by thermal imaging. The field‐enhancement surfaces enhance the emissivity of the patterns, in turn reduce the minimum temperature to detect the thermal emission down to ≈30 °C from >150 °C to exploit ubiquitous heat sources like the human body. The study provides a framework for the use of thermal emitters as optical security features and demonstrates applications on rigid and flexible substrates.

中文翻译：

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具有强红外发射的不可见薄膜图案作为光学安全功能

光谱选择性热发射对热光电，辐射冷却和红外传感应用有很高的要求。历史上，通过选择具有合适红外特性的材料来实现发射率的光谱控制。纳米制造技术的最新进展可增强光-物质相互作用，从而实现了自然无法获得的光学特性（如红外发射率）。在这项研究中，提出了在场增强表面上基于纳米厚电介质的热辐射器，作为光学安全功能。通过在可见光中透明并在热像仪的光谱范围内表现出强烈的红外吸收的超薄介电层产生图案，可以实现这种功能。然后通过热成像显示不可见的图案。场增强表面提高了图形的发射率，进而降低了最低温度，以检测从> 150°C降至≈30°C的热辐​​射，从而利用人体等普适的热源。这项研究提供了将热辐射器用作光学安全功能的框架，并演示了在刚性和柔性基板上的应用。