Multistate spectral-tunable manipulation of mid-infrared emissivity using Sb₂S₃/GST/VO₂

Conventional thermal emission that exhibits spectral selectivity relies on micro/nanostructures, such as gratings, photonic crystals, photonic cavities, nanoantennas, and metamaterials. By utilizing advanced micro/nanofabrication techniques to modify the structural parameters of the micro/nanostructures, it is possible to create wavelength-selective thermal emitters that span from THz to the visible range. Nonetheless, static micro/nanostructures do not offer flexible tunability in terms of thermal emissivity. In this Letter, we report a conceptual design of a multistate multilayered structure using a combination of three phase change materials: VO2, Ge2Sb2Te5, and Sb2S3. By controlling the temperature, the phase change materials will be in different phase states, rendering the multilayered structure six feasible thermal states with tunable spectra in the mid-infrared range. The impact of layer thickness is investigated. Polarization independence and angle insensitivity are exhibited until a large incident angle. This multilayered thermal structure is lithography-free and industrially scalable, showing great potential for programmable photonics and thermal sensors.