In this Information Age, digital electronics have become a crucial part of our everyday lives. Binary, or Boolean, logic has become ubiquitous in a society so closely affiliated with personal electronics. The deceptively simple nature of the mathematical structure that uses 1s and 0s has enabled applications across a range of varied scientific fields.
In the September 14 issue of Nature Materials (DOI: 10.1038/NMAT4082), researchers at the University of Pennsylvania have proposed new methods of producing optical system designs using digital metamaterial “bits” and “bytes.” Using simulations constructed with the COMSOL Multiphysics software, the researchers simulated the effective permittivity of two-component structures they label as metamaterial bytes; these were generated in both two-dimensional (2D) rectangular and concentric core–shell configurations. Each byte consisted of two bits, here comprising Ag and SiO2. It was seen that by altering factors such as bit order, relative bit size, and orientation of the incident wave’s electric-field polarization, significant changes in the effective permittivity of the byte could be achieved. Additionally, permittivity values could be produced anywhere between the values of the two bits or even outside that range. Thus, it was demonstrated that, given the right conditions, a wide range of effective permittivity values could be produced from just two materials. Furthermore, the electromagnetic wave scattering from the digital bytes was found to be comparable to analogous homogenized structures.
The researchers substantiated the use of these digital metamaterial bytes in a number of design structures. The core–shell digital bytes performed well in an arrangement designed to mimic a dielectric convex lens with a hyperbolic profile. By altering the order and thickness of the material bits within these core–shell bytes, a 2D graded-index flat lens architecture could also be produced. By constructing the grading in this lens from discrete, subwavelength cross-sections, spatial variation of permittivity can be controlled to a greater degree. With confirmation that these digital metamaterial bytes function well in a number of system designs, this work opens up the possibility of developing simpler, more controllable device architectures.
