| Abstract: | A highly directional thermal emitter device comprises a two-dimensional
periodic array of heavily doped semiconductor structures on a surface of
a substrate. The array provides a highly directional thermal emission at
a peak wavelength between 3 and 15 microns when the array is heated. For
example, highly doped silicon (HDSi) with a plasma frequency in the
mid-wave infrared was used to fabricate nearly perfect absorbing
two-dimensional gratings structures that function as highly directional
thermal radiators. The absorption and emission characteristics of the
HDSi devices possessed a high degree of angular dependence for infrared
absorption in the 10-12 micron range, while maintaining high reflectivity
of solar radiation (.about.64%) at large incidence angles. |