Broadband high-temperature thermal emitter/absorber designed by the adjoint method

Broadband thermal emitters/absorbers are of great interest for thermal management in high-temperature applications including thermophotovoltaics and hypersonics due to the dominance of radiative heat transfer. Several studies have been reported, which benefit from the effectiveness of photonic structures on wave coupling tuned by parametric sweeps and intuition. However, the higher emission/absorption potential of structures with nonintuitive geometries due to increased number of available design parameters has not been explored. To address this need, we have studied gradient-based topology optimization for the design of high-temperature thermal emitters/absorbers. By utilizing the adjoint method, which allows gradient calculation only with two simulations, more complex geometries that exhibit higher emission/absorption in the broadband spectrum are designed. ZrB2 is chosen as the coating material, which belongs to the family of ultrahigh-temperature ceramics (UHTC), due to its very good thermomechanical properties. Emission/absorption rates reaching up to 85% levels in the broadband spectrum are achieved, which is around 40% levels in film form. Electromagnetic phenomena that give rise to elevated emission/absorption are also analyzed. Our findings demonstrate the potential of effectiveness of ad joint-based topology optimization in the broadband spectrum and high emission of ZrB2 when patterned, which, to the best of our knowledge, was not previously explored. (C) 2021 Optical Society of America