Optimization of stacked Fabry-Perot cavities for VO2-based broadband adaptive thermal radiators

Abstract

The performance of an adaptive thermal radiator (ATR) for temperature regulation depends on its ability to modulate spectral emissivity across a broad wavelength range. For a single cavity, we found that the tunable, thermal emissivity from 2-30 µm is maximized using a spacer material with low n and k, such as BaF2 . However, a single cavity produces a narrowband peak in the spectral emissivity. Stacking multiple cavities introduces additional resonances that create high-temperature spectral emissivity peaks. Here, we designed cavities composed of VO2 and BaF2 to have different resonant wavelengths to demonstrate a broadband response across the infrared spectrum out to ∼30 µm. In this work, we find that up to three cavities increases the tunable thermal emissivity with negligible changes from additional cavities.