Such structures control reflected waves in amplitude, phase and polarization through constructive and destructive interference of scattering contributions from a ground plane and a scatterer array. An important family of examples is that of perfect absorbers like Salisbury screens, and patch-antenna reflective metasurfaces, in which arrays of resonant antennas are placed in front of a reflector, ,, ,, ,, ,. Second, seminal early examples of metasurfaces use stacking to design function. First, if one considers metasurfaces as objects that transform incident wavefronts according to designed mathematical functions in the context of signal processing and computation, ,, an important question is how you can concatenate optical functions stacking metasurfaces. Understanding the physics of layered systems in which metasurfaces are stacked in succession, or interspersed with normal metal and dielectric layers, is of large relevance from several viewpoints. In this work we focus on 2D arrays where the constituents are strong, resonant scatterers with a dipolar plasmonic resonance, as opposed to dielectric metasurfaces. Recent demonstrations of metasurfaces include a large variety of flat optics components, such as lenses, ,, , waveplates and polarization optics, ,, as well as holograms, ,, diffusers, and even computational metasurfaces that are designed to perform simple linear mathematical operations on incident wavefronts. This notion revitalized a venerable history in grating science, particularly the notion of echelette gratings to shape diffraction. This boundary condition is realized by engineering subdiffractive arrays of building blocks that are arrayed in a 2D sheet. In contrast to the notion of metamaterials that were designed to realize 3D bulk materials with peculiar designer permittivity and permeability, the notion of metasurfaces is that they shape waves by scattering off of an abrupt designer boundary condition with a completely controlled and locally varying amplitude and phase. Since almost a decade metasurfaces have emerged as a very fast growing field of research in nanophotonics.
0 Comments
Leave a Reply. |