Directional Thermal Emission Covering Two Atmospheric Windows

Controlling directional thermal emission to match the ultra-broadband atmospheric window is a long-standing scientific challenge. Here, a strategy is introduced for achieving ultra-broadband directional thermal emission matching the atmospheric window by combining Fabry-Perot resonances and the Brewster effect. The planar system, comprising a thin dielectric film (Ge) on a radiative substrate, exhibits high p-polarized emissivity (> 0.9) at specific directions (76(degrees)-84(degrees)) covering the entire atmospheric window (3-5 and 8-14 mu m) and high omnidirectional emission (> 0.7) in the non-atmospheric window (5-8 mu m) for simultaneous efficient radiative cooling. Moreover, it can integrate independent dual-band (visible-IR) information encryption and the infrared information anti-snooping function. The approach offers unique insights into controlling thermal emission using planar films, with broad implications in camouflage, thermal management, and encryption.