Phase-change-based polarization-selective switching for multilevel emittance modulation

Smart modulation of emittance of a radiator, particularly through multilevel strategies, has garnered substantial interest due to its unparalleled adaptability and versatility. In this Letter, we present a smart multilevel radiator, capable of achieving four distinct levels of emittance modulation in the spectral range of 2.5-30 μm. Such a smart radiator is a relatively straightforward design, integrating In₃SbTe₂ (IST)-based linear grating on a VO₂-based multilayer structure. The enhanced emittance tunability of the smart multilevel radiator is achieved, with total normal emittances of 0.11, 0.27, 0.54, and 0.82 for the four levels, respectively. The underlying mechanisms involve manipulating the Fabry-Perot (FP) resonance through the phase change of VO₂ and in-plane anisotropy via the phase change of IST. The multilevel modulation of emittance exhibits remarkable stability and excellence under wide-angle incidence conditions. The development of this multilevel smart radiator has considerable potential for applications in thermal anti-counterfeiting, thermal management, and energy conservation.