Broadband metamaterial absorber based on a multi-layer structure

Abstract

In this paper, a broadband metamaterial absorber (MA) based on a multi-layer structure is presented. The advantages of this MA are the small periodic unit size, they are thin, have excellent polarization characteristics and are adaptive for wide angles of oblique incident electromagnetic waves. The unit cell of the broadband MA is composed of three dual-band sub-cells; each presents two resonant frequencies so as to form a wide absorptive spectrum when stacked. The sandwiched dual-band sub-cell is composed of one metallic annular patch and one metallic circular patch each etched on a lossy substrate. The radii of the metallic patches forming each sub-cell are different so as to appear to have different resonant frequencies. In the design of the unit cell there are metallic circular patches and an air layer at the bottom of each sub-cell to form magnetic coupling and avoid coupling between sub-cells. The broadband MA presents good absorptivity above 80% between 8.8 and 10.8 GHz, with a full width at half maximum (FWHM) absorption bandwidth of 2.3 GHz and a relative FWHM absorption bandwidth of 23%.

Broadband absorption in mid-infrared metamaterial absorbers with multiple dielectric layers

“…However, the inherent resonant nature of metamaterials determines that the absorption bandwidth of MAs is usually narrow, which has thus restricted MAs from more extensive applications such as the energy harvesting. Efforts have been made to extend the absorption bandwidth through the concept of multiresonances [13][14][15][16][17][18]. Multiresonant broadband absorbers are generally realized by the elaborate blending of dimensionally dispersed metallic resonators either vertically [13][14][15] or horizontally [16][17][18].…”

“…However, the designs in Refs. [13][14][15] need to precisely align several resonators between the layers, making the fabrication process very complicated; while the designs in Refs. [16][17][18] cannot broaden the absorption bandwidth significantly because it is quite difficult to arrange many different sizes resonators in one unit-cell.…”

Tailoring terahertz electromagnetic responses of bilayer metamaterials

“…In planar MMs, the combination with more different units means certainly s reduction of relative function unit densities, and as a consequence, the required EM responses are inevitably weakened. Recently, some researchers have arranged SRRs' MMs layer-by-layer using dielectric spacers to form a quasi-three-dimensional bulk [24][25][26][27][28][29][30]. In such bulk MMs, EM responses with unique properties can be purposefully modulated.…”

“…Most of those researches are focusing on the novel but complex coupling interactions between the elements in different layers [24][25][26], when the thickness of the spacer layer is much smaller than the wavelength. When the spacer thickness becomes larger, superposition effects are found between different layers, which can be applied in a broadband absorber or filter [27][28][29][30] of the unit elements remain unchanged after stacking different layers together, the target multi-responses can be ''tailored'' by simple combination of pre-marked MMs layers. This is very convenient for an easy and quick design for target multi-responses in noticeably underutilized THz sensing, which is a promising technology in many research fields, such as medical and biological applications.…”

Polarization-Insensitive Triple-Band Microwave Metamaterial Absorber Based on Rotated Square Rings

“…However, the high absorption of the MA is generally based on electromagnetic resonances, so its working bandwidth is relatively narrow. Recently, most of efforts are made on MAs to achieve polarization-insensitive absorption [3][4][5], wideangle absorption [6][7][8], multi-band absorption [9][10][11][12][13][14], and broadband absorption [15][16][17][18]. Up to now, the MAs have been demonstrated in every technologically relevant spectral range, from the microwave region [1-5, 9-14, 17, 18], the terahertz region [6,15,16], to the infrared region [7,19], and even to the optical region [8,20].…”