Broadband Radiative Heat Transfer Suppression via Dispersion-Engineered Metasurfaces.

Suppressing radiative heat transfer using metallic reflectors fails where electrical conduction or material incompatibility are prohibitive, whereas non-metallic alternatives that rely on conventional thermophotonic approaches face fundamental performance-bandwidth trade-offs, bounded by the Bode-Fano limit. Here, we redefine the strategy for broadband radiative suppression by leveraging complementary dispersion engineering in a dielectric metasurface pair. Using stochastic gradient descent (SGD) optimization, we co-design aperiodic distributed Bragg reflector (DBR) pairs with deliberately misaligned passbands across the broad thermal band of interest, enabling effective broadband thermal decoupling within a small thickness and fabrication budget, beyond the limits of conventional approaches. Experimental validation reveals that our optimized 7-layered (7-L) metasurface pair reduces radiative heat exchange significantly compared to fused silica benchmarks, as confirmed through both angle-resolved emissivity measurements (82% reduction) and direct radiometric power quantification (62.5% reduction). Importantly, our compact system exhibits strong robustness against design and fabrication tolerance and operational temperature drift (320-500 K). This work establishes a generalizable framework for bandwidth-unconstrained thermal radiation engineering, with applications in energy-efficient systems, thermal insulation and thermal management. By circumventing the need for metallic components, our approach opens new possibilities for controlling radiative heat transfer in an all-dielectric ultrathin platform.