Broadband hyperbolic thermal metasurfaces based on the plasmonic phase-change material In₃SbTe₂

Thermal radiation modulation facilitated by phase change materials (PCMs) needs a large thermal radiation contrast in broadband as well as in a non-volatile phase transition, which are only partially satisfied by conventional PCMs. In contrast, the emerging plasmonic PCM In₃SbTe₂ (IST) that undergoes a non-volatile dielectric-to-metal phase transition during crystallization offers a fitting solution. Here, we have prepared IST-based hyperbolic thermal metasurfaces and demonstrated their capabilities to modulate thermal radiation. By laser-printing crystalline IST gratings with different fill factors on amorphous IST films, we have achieved multilevel, large-range, and polarization-dependent control of the emissivity modulation (0.07 for the crystalline phase and 0.73 for the amorphous phase) over a broad bandwidth (8-14 μm). With the convenient direct laser writing technique that supports large-scale surface patterning, we have also demonstrated promising applications of thermal anti-counterfeiting with hyperbolic thermal metasurfaces.