title: Buried nanoantenna arrays: versatile antireflection coating.
abstract: Reflection is usually a detrimental phenomenon in many applications such as flat-panel-displays, solar cells, photodetectors, infrared sensors, and lenses. Thus far, to control and suppress the reflection from a substrate, numerous techniques including dielectric interference coatings, surface texturing, adiabatic index matching, and scattering from plasmonic nanoparticles have been investigated. A new technique is demonstrated to manage and suppress reflection from lossless and lossy substrates. It provides a wider flexibility in design versus previous methods. Reflection from a surface can be suppressed over a narrowband, wideband, or multiband frequency range. The antireflection can be dependent or independent of the incident wave polarization. Moreover, antireflection at a very wide incidence angle can be attained. The reflection from a substrate is controlled by a buried nanoantenna array, a structure composed of (1) a subwavelength metallic array and (2) a dielectric cover layer referred to as a superstrate. The material properties and thickness of the superstrate and nanoantennas' geometry and periodicity control the phase and intensity of the wave circulating inside the superstrate cavity. A minimum reflectance of 0.02% is achieved in various experiments in the mid-infrared from a silicon substrate. The design can be integrated in straightforward way in optical devices. The proposed structure is a versatile AR coating to optically impedance matches any substrate to free space in selected any narrow and broadband spectral response across the entire visible and infrared spectrum.
authors.affiliation: School of Engineering and Applied Sciences (SEAS), Harvard University , Mckay Gordon Building, Capasso Lab, Room 125, Cambridge, Massachusetts 02138, United States.
authors.forename: Ali
authors.initials: A
authors.lastname: Kabiri
authors.forename: Emad
authors.initials: E
authors.lastname: Girgis
authors.forename: Federico
authors.initials: F
authors.lastname: Capasso
mesh_terms: D008027:Light; D053758:Nanoparticles / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D055096:Optical Devices; D055095:Optics and Photonics; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D012825:Silicon