Plasmonic antireflection coatings in the infrared

Antireflective (AR) coatings are used in many optical applications such as flat-panel displays, solar cells, lasers and other optoelectronic devices. Until recently, efforts for realizing low surface reflectivity have been concentrated on thin dielectric films, where the structural profile of the film is used to create a gradual change in the refractive index between the air and substrate. As an alternative to this approach, there has been much interest in pushing frequency-selective-surface (FSS) technology, a technology which is well known in the literature for its filtering characteristics at microwave and millimeter frequencies, to infrared frequencies. With FSSs (examples include periodic conducting elements placed on a dielectric substrate or apertures perforating a conducting sheet), the filtering response is realized due to the photon-plasmon coupling associated with the structured periodic surface rather than through an impedance-matching concept. Following along the path of the microwave community, attention in this work is confined to the transmission response of single-layer aperture-array screens, with the goal of ultimately realizing an AR surface with a high angular and frequency bandwidth in the mid-infrared frequency range.