The surface grating structures designed by the numerical calculations are fabricated on Si substrates by using micromachining technique. We have used the dry etching process. The patterns are fabricated by photolithography, and the Si substrates are etched by the reactive Ion etching (RIE) technique. A typical SEM image is shown in Fig. 8. The scale of fabricated grating is almost the same as the designed values. Since Si is transparent in this wavelength region, Pt film is deposited after fabrication. The thickness of the film is about 200nm. The optical reflectance shows a typical absorption due to the micro cavity effect as predicted by the simulation.

2. Conclusions

The sky radiators with spectrally selective emission surface are designed by using the principle of diffraction optics. The surface grating shows high spectral emissivity at the atmospheric window region. By using numerical simulation of RCWA, the optimum design parameters of surface grating structures are determined in this study. The estimated cooling power shows very high performance. Surface grating are fabricated on Si substrates by using micromaching technique. The development of processes to fabricate the large area radiator is essential to practical applications.