Wave-Shaping Surfaces

Abstract

Huygens' principle is a well-known concept in electromagnetics that dates back to 1690. Here, it is applied to develop designer surfaces that provide extreme control of electromagnetic wave fronts across electrically thin layers. These reflectionless surfaces, referred to as metamaterial Huygens' surfaces, provide new beam shaping, steering, and focusing capabilities. The metamaterial Huygens' surfaces are realized with two-dimensional arrays of polarizable particles that provide both electric and magnetic polarization currents to generate prescribed wave fronts. A straightforward design methodology is demonstrated and applied to develop a beam-refracting surface and a Gaussian-to-Bessel beam transformer. Metamaterial Huygens' surfaces could find a wide range of applications over the entire electromagnetic spectrum including single-surface lenses, polarization controlling devices, stealth technologies, and perfect absorbers.

Anomalous three-dimensional refraction in the microwave region by ultra-thin high efficiency metalens with phase discontinuities in orthogonal directions

“…Then, the coupling efficiency for the cross-pol wave can be calculated, based on equation (1), to be above 20% for the frequency range from 8.9 GHz to 10.2 GHz (the light grey region in figure 1(b), 13.6% relative bandwidth). The result is also in accordance with the transmission coefficient of the left-handed circular polarization (LCP) under the right-handed circular polarized (RCP) incidence, which is relatively high compared with the current results and almost reaches the theoretical limit [22,23].…”

“…However, the transmission-type metalens, which particularly operates upon the cross-pol wave, faces the challenge of extremely low conversion efficiency. The maximum efficiency achieved was only a few per cent [8-10, 14-16, 21], which could be a great obstacle for the applications, although it was predicted theoretically that the maximum attainable cross-coupling is 25% based on the S-parameters of the four-port network [22,23]. The thinner-than-wavelength Huygens' surface is also put forward to fulfil the manipulation of the wavefront, which exhibits high transmission efficiency, and 30% in the infrared region [24] and 90% in the microwave region [25] can be achieved owing to impedance matching by both the electric and magnetic response.…”

“…The thinner-than-wavelength Huygens' surface is also put forward to fulfil the manipulation of the wavefront, which exhibits high transmission efficiency, and 30% in the infrared region [24] and 90% in the microwave region [25] can be achieved owing to impedance matching by both the electric and magnetic response. However, it is important to note that [24] and [25] do not deal with the cross-pol conversion and are therefore free from the imposed theoretical limit at 25% [22,23]. On the other hand, the transverse magnetic currents require loops perpendicular to the screen, which implies that a finite minimum thickness (0.28 λ in [24] and 0.2 λ in [25]) is a must.…”

Extreme coupling: A route towards local magnetic metamaterials

“…However, most of these applications, such as shaping the wave beams, polarization transforms, frequency and polarization selective absorption (see, e.g., Refs. [2][3][4][5][6][7]), and some others require strictly local metamaterials. These are metamaterials where the electric and magnetic response represented by permittivity ε ij (ω) and permeability μ ij (ω) only depends on the frequency ω.…”

Metamaterials for Microwave Radomes and the Concept of a Metaradome: Review of the Literature

“…Conventional optical lenses can be replaced with planar metasheets as shown in Figure 7 [51]. Several metasheets combined together may work as a metamaterial with a negative index of refraction.…”