Coating Reflects Almost No Light

Conventional antireflective coatings are effective only for a single wavelength of light and when the beam is oriented perpendicular to the coated surface. Rensselaer Polytechnic Institute engineer E. Fred Schubert and colleagues have now designed a coating that virtually eliminates reflection over a broad range of wavelengths and angles of incoming light—a first for thin films. These features could be useful for applications including more efficient solar cells and brighter light-emitting diodes. What's the secret behind the new coating? A thicket of tilted nanorods. Using electron-beam deposition, the researchers coated a base of aluminum nitride with three layers of angled titanium dioxide nanorods topped by two layers of angled silica nanorods. The resulting coating, which is about 600 nm thick, has a refractive index of 1.05 at the surface, the lowest ever for a thin film, according to Schubert (Nat. Photonics 2007, 1, 176).