Abstract-Broadband terahertz metamaterial absorber based on simple multi-ring structures

AIP Advances

Guoqing Shen, Ming Zhang, Yanping Ji, Wanxia Huang, Honglin Yu,  Jianping Shi,

Three-dimensional diagram of the unit cell (a) and top view (b) of the terahertz metamaterial absorber. P is the period of the unit cell, L is the length of the metal square ring and a, b, c, d represent four sub-cells, respectively.

https://aip.scitation.org/doi/10.1063/1.5024606

Single-layer metallic rings are the effective structure cell which are widely used to design single-band and multiband perfect metamaterial absorbers owning to their electromagnetic resonance. However, the absorbers based on the single-layer metallic rings have a common shortcoming, that is the narrow absorption bandwidth. To overcome the limitations, here we proposed a single-layer, flexible and broadband terahertz metamaterial absorber, which consists of four sub-cells with multiple metal rings and a metal ground plane separated by a dielectric layer. By enhancing the coupling response between adjacent metallic rings and merging the adjacent resonant peaks of multi-resonators, we experimentally observed broadband characteristics at the terahertz band. The average absorption of 88% from 0.63 to 1.34 THz and the relative absorption bandwidth of 95% at the incident angle of 15o for TE polarization. Correspondingly, for TM polarization the absorption of more than 80% from 0.61 to 1.1 THz with the relative absorption bandwidth of 80% were also observed. The results went far beyond the previous single-layer absorbers based on metal rings and were much better than the fractal-cross structure reported recently [Kenney et al., ACS Photonics 4, 2604 (2017)]. We had reason to believe that the presented terahertz metamaterial absorber with broad absorption bandwidth and simple structure can find important applications in communication, stealth, energy harvesting systems and so on.

Abstract-Tailoring Infrared Refractory Plasmonic Material to Broadband Circularly Polarized Thermal Emitter

Maowen Song, Honglin Yu, Jun Luo, Zuojun Zhang

http://link.springer.com/article/10.1007/s11468-016-0310-6
Circularly polarized (CP) thermal emission possesses huge application value in the fields of infrared detecting and polarimetric thermal imaging; however, the naturally occurring infrared source is incoherent and unpolarized. In this paper, we designed a broadband CP source adaptive for high temperature in consideration of the collision frequency of the electrons increasing with temperature. Compared with the structure proposed before, “I”-shaped resonators based on refractory plasmonic material generate the linearly polarized (LP) emission and the dielectric quarter-wave plate enhances the degree of emitted CP by suppressing the parasitic radiation. More than 80 % right-handed circularly polarized (RCP) emissivity in wavelengths ranging from 3.28 to 4.81 μm within 706 to 884 K is theoretically achieved.

Abstract-Highly efficient wavefront manipulation in terahertz based on plasmonic gradient metasurfaces

Jun Luo, Honglin Yu, Maowen Song, and Zuojun Zhang  »View Author Affiliations

Optics Letters, Vol. 39, Issue 8, pp. 2229-2231 (2014)
http://dx.doi.org/10.1364/OL.39.002229

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-39-8-2229

Polarization conversion efficiency is vitally important to highly efficient wavefront manipulation based on phase discontinuities. However, previous single-layer phase gradient metasurfaces have suffered from low polarization conversion efficiency (at most 25%). Here we present a three-layer structure to enhance polarization conversion efficiency. The average efficiency is 76% for circularly polarized incident light converted to its opposite handedness. By arraying metallic antennas with varied optical axes for circularly polarized incident light, the efficiency of anomalous refraction is apparently increased, and the focused intensity of flat lenses can be significantly enhanced in the terahertz regime. It is expected that this scheme has potential applications in detection, focusing, and imaging.

© 2014 Optical Society of America