A surface wave (SW) in optics is a light wave, which is supported at an interface of two dissimilar media and propagates along the interface with its field amplitude exponentially decaying away from the boundary. Research on surface waves has been flourishing in the last few decades due to their unique properties of surface sensitivity and field localization. These features have resulted in applications in nano-guiding, sensing, light-trapping and imaging based on near-field techniques, contributing to the establishment of nanophotonics as a field of research. Up to now, a wide variety of surface waves has been investigated in numerous material and structure settings. This article reviews the recent progress and development in the physics of SWs localized at metamaterial interfaces, as well as bulk media in order to provide broader perspectives on optical surface waves in general. For each type of surface wave, we discuss the material and structural platforms. We mainly focus on experimental realizations in the visible and near-infrared wavelength ranges. We also address existing and potential application of SWs in chemical and biological sensing, and experimental excitation and characterization methods.

https://iopscience.iop.org/article/10.1088/1361-648X/aa8bdd/pdf

Photonic surface waves on metamaterial interfaces

A frequency selective surface (FSS) with miniaturized elements based on a quarter-mode substrate integrated waveguide (QMSIW) is proposed and investigated in this paper. The periodic element includes the QMSIW cavity and two L-type slots etched on the top and bottom conductor claddings of the cavity. The slot not only performs as the equivalent magnetic wall of the QMSIW FSS element but also provides a pole near the resonant frequency of the QMSIW cavity to improve the passband characteristics of the FSS. In this case, the size of the conventional FSS element can be reduced by 65% at the same operation frequency while keeping a similar performance. Based on this miniaturized element, the frequency interval between the passband and the first parasitic passband can increase 2.7 times compared with that of a conventional SIW FSS. As an example, an X-band QMSIW FSS is designed, fabricated, and measured. Besides, it is insensitive to the incident angle and polarization of the incident wave. Such a miniaturized FSS element can also be employed in the design of a multiband FSS with controllable transmission zeroes.

Frequency Selective Surface With Miniaturized Elements Based on Quarter-Mode Substrate Integrated Waveguide Cavity With Two Poles

We propose an unprecedented transmit-array configuration which can mold the incident beam by modulating phase and amplitude wavefronts. The transmit-array is composed of patterned graphene metasurfaces as shunt admittance sheets. Thanks to the exceptional features of graphene such as tunability, thinness, low loss, and high confinement of graphene plasmons, the proposed subwavelength structure passes strict touchstones for nano-photonic and opto-electronic applications. Two flat-optics functionalities, i.e., focusing and splitting, are realized by means of the proposed configuration.

/pdf/beam-manipulating-by-gate-tunable-graphene-based-3vqf0muif0.pdf

Beam manipulating by gate-tunable graphene-based metasurfaces.

A novel metamaterial (MTM) element for radome applications is presented in this paper, which shows negative permittivity and permeability characteristics at distinct frequency ranges. The MTM element is composed of tightly coupled Swastika-shaped conductors printed on both sides of the dielectric substrate. The electromagnetic (EM) analysis of the proposed structure is carried out using the full-wave method-based standard software package and then validated with the experimental results. The MTM structure is further modified by introducing shorting strips at its edges to improve bandpass FSS response with flat-top and sharp roll-off characteristics in microwave and millimeter-wave frequency regimes. In view of airborne radome application of MTM-FSS structure, a multilayered hemispherical radome is designed by embedding it in the mid-plane of the radome wall. The EM performance of the antenna–radome system is analyzed using 3-D ray tracing geometrical optics in conjunction with aperture integration method, incorporating the transmission characteristics of MTM-FSS-based radome wall using CST Microwave Studio. The MTM-FSS-based radome exhibits superior EM performance characteristics as compared to the conventional optimized monolithic radome over the frequency range of 8.5–10.3 GHz, with high transmission efficiency (~0.30) and minimal boresight error (~4 mrad) for the entire beam steering range.

Novel Metamaterial-Element-Based FSS for Airborne Radome Applications

Perfect light absorbers have attracted much attention because of their potential applications in solar cells, thermal imaging, material detection, bio-sensing, and others. However, it is extremely difficult to obtain the ultra-narrow bandwidth of a perfect light absorber in the terahertz region. Herein, an ultra-narrow terahertz perfect light absorber based on the surface lattice resonance of three stacking layers, namely a square resonator, a dielectric spacer, and a metallic film, is reported. A resonance absorption peak with bandwidth of 0.0200 THz and absorption rate of 98.86% is realized. The absorption performance of the device can be controlled by employing different sized (unit) periods and dielectric spacer thicknesses. Particularly, the device bandwidth can be decreased by reducing the dielectric layer thickness. At a certain thickness, a resonance peak with a bandwidth of only 0.0067 THz is achieved. This peak is very sensitive to the surrounding refractive index. The large sensitivity (2.58 THz per refractive index) and simultaneous ultra-narrow bandwidth lead to an ultra-high figure of merit (385.07), making this a promising light device in terahertz detection and sensing.

https://pubs.rsc.org/en/content/articlepdf/2017/ra/c7ra08413g

Ultra-narrow terahertz perfect light absorber based on surface lattice resonance of a sandwich resonator for sensing applications

A switchable Frequency Selective Surface (FSS) in which the switchable elements are Plasma-shells. Plasma-shells as described herein allow for control or ‘reconfiguration’ of the FSS electromagnetic (EM) properties.

Lee W. Cross

Papers

Frequency Selective Surfaces