Achievement

As the dimensions of a metallic photonic crystal get closer to the visible wavelengths, the material properties begin to dominate the optical properties of the structure. At long wavelengths, the metal behaves like a perfect conductor, but in the near infrared, interband transitions become significant and most metals have high absorption in this range. In tungsten this occurs below 3 um. By coating as-fabricated tungsten woodpile 3D photonic crystal structures with a thin layer of higher refractive index iridium, it was found that the photonic band edge could be pushed to below 1 um. This allows for thermal emission peaks to be pushed further into the near-IR wavelengths while limiting longer wavelength tail radiation due to high material absorption that exists below 2 um. This exciting work is performed by IGERT trainee Tim Walsh and the manuscript, "A high temperature metal coating for modification of photonic band edge position", is under review by J. of the Optical Soc. of Am. B.