Temporal aiming

Abstract

Deflecting and changing the direction of propagation of electromagnetic waves are needed in multiple applications, such as in lens-antenna systems, point-to-point communications and radars. In this realm, metamaterials have been demonstrated to be great candidates for controlling wave propagation and wave-matter interactions by offering manipulation of their electromagnetic properties at will. They have been studied mainly in the frequency domain, but their temporal manipulation has become a topic of great interest during the past few years in the design of spatiotemporally modulated artificial media. In this work, we propose an idea for changing the direction of the energy propagation of electromagnetic waves by using time-dependent metamaterials, the permittivity of which is rapidly changed from isotropic to anisotropic values, an approach that we call temporal aiming. In so doing, here, we show how the direction of the Poynting vector becomes different from that of the wavenumber. Several scenarios are analytically and numerically evaluated, such as plane waves under oblique incidence and Gaussian beams, demonstrating how proper engineering of the isotropic-anisotropic temporal function of ε r (t) can lead to a redirection of waves to different spatial locations in real time.

Metamaterials with high degrees of freedom: space, time, and more

“…Moreover, it is also known that in anisotropic media the direction of phase flow (i.e., the wave vector) is not necessarily the same as the direction of energy flow (i.e., the Poynting vector). These two features have been recently utilized in developing new phenomena of the inverse prism [46], in which after the rapid change of refractive index from isotropic to an anisotropic set of values the waves experience different frequencies in different directions of propagation, and the temporal aiming [47], in which the direction of energy propagation for a wave packet can change midstream by rapid change of permittivity from an isotropic to an anisotropic case. Together with my collaborators, we are currently investigating various aspects of such 4D metamaterials with high degree of freedom.…”

Hyperbolic Metamaterials via Hierarchical Block Copolymer Nanostructures

“…[3] These materials show some exotic optical properties that are unattainable in bulk structures, such as negative refraction [4] and a broadband enhancement of the local density of optical states (LDOS), [5] with the advantage that the optical behavior can be tuned by properly designing the meta-atoms. [6] These unconventional properties open many opportunities for controlling the confinement and propagation of electromagnetic waves at the nanoscale in time and space, [7,8] with intriguing consequences in different fields and applications. [9] To date, most of the HMMs presented in the literature are realized by sequential growth or deposition of metal/dielectric multilayers [10] or by electrodeposition in nanoporous templates.…”

Temporal interfaces and metamaterial response enabled by boundaries

“…It is clear that the possibility to control the scattering also using the time dimension have drawn significant attention in recent years [3,4]. Like in single or multilayered spatial structures, playing with the temporal sequence and application time of the materials over the propagation period enables plenty of intriguing wave phenomena [5], e.g., inverse prism [6], temporal aiming [7], and synthesis of effective media [8], as well as novel devices in time-domain, e.g. antireflection coatings [9,10], temporal Fabry-Perot cavities [10], spacetime crystals [11], and broadband absorbers [12].…”