Pan, SSun, YLiu, XZhou, XZhang, SSun, SWang, X2025-06-192025-06-192025-10-150927-0248https://hdl.handle.net/10161/32504In this work, we designed and optimized a one-dimensional (1D) photonic crystal (PhC) for the application of a thermal radiation barrier. The insulation relies on the omnidirectional bandgap to reflect electromagnetic radiation regardless of its incident angle and polarization. As thermal radiation has a broadband spectrum that depends on both wavelength and angle, a cascaded and differentiated waveband design was utilized. The optimized omnidirectional reflector (ODR) is composed of germanium (Ge) and magnesium fluoride (MgF<inf>2</inf>), consisting of 4 differentiated patterns with 2 periods each to have the maximum insulation performance within reasonable fabrication costs. For a 1200 K blackbody radiator, the heat retaining rate can reach 93.5 % within a thickness of 13 μm. We analyzed the role of each pattern and substantiated the methodology of differentiated waveband design, which can be generalized to other photonic designs for thermal insulation. We further assessed potential uncertainties induced by fabrication processes and material properties. The reflector can retain above 90 % of the radiative heat from high-temperature sources when the thickness variation is within 13 % of the designed values, even incorporating the largest optical constant differences used in this work. The broadband ODR with a differentiated design may provide an optimal solution to insulate radiative heat for ultra-high temperature and small-scale heat sources, surpassing conventional solutions provided by metallic coating or multilayer insulation.https://creativecommons.org/licenses/by-nc/4.0Journal article