Spectrally selective thermal radiators and absorbers with periodic microstructured surface for high-temperature applications

Spectral absorptance and emittance of W surface gratings with short periodicity corresponding to the VIS to NIR wavelengths have been investigated to develop spectrally selective devices for high-temperature applications, such as selective solar absorbers and selective radiators for thermophotovoltaic systems. Numerical calculations based on rigorous coupled-wave analysis have been performed to evaluate the grating parameters. Two kinds of W surface gratings composed by microcavities have been fabricated by fast atom beam etching with two different lithography techniques. These gratings have shown strong absorption or emission due to the surface microstructures in the VIS to NIR region, whereas their reflectance in the IR region is kept at a high level. Their high thermal stability is confirmed from heating tests under vacuum or reduced atmospheres. Physical aspect of the interaction of electromagnetic wave with lossy gratings has also been discussed briefly.