Reststrahlen material bilayers: an option for tailoring in the infrared

Double-layer interference calculations are used to show that the frost-preventing properties of insulating beryllium oxide can be improved. An underlying substrate of cubic boron nitride, which has a short-wavelength reststrahlen band, will reduce the thermal radiation leak of beryllium oxide in the 8-9.5 interval. The interference calculations for these highly dispersive and partly absorbing materials demonstrate that the configuration with beryllium oxide as an outer layer is essential for the performance. Less than 20% average emittance and 11 W/m(2) irradiance in the 8-13-µm window is predicted when an optimum thickness of 2.5-µm beryllium oxide upon cubic boron nitride is used.