Abstract-Enhanced Confinement of Terahertz Surface Plasmon Polaritons in Bulk Dirac Semimetal-Insulator-Metal Waveguides

Yi Su, Qi Lin, Xiang Zhal, Ling-Ling Wang

https://nanoscalereslett.springeropen.com/articles/10.1186/s11671-018-2686-z

A subwavelength terahertz plasmonic waveguide based on bulk Dirac semimetal (BDS)-insulator-metal (BIM) structure is investigated, which indicates that there is an optimized frequency range with the better confinement as well as lower loss. A broadband mode confinement up to λ0/15 with a relatively low loss of 1.0 dB/λ0 can be achieved. We also show that two silicon ribbons introduced into the BIM waveguide can form a dynamically tunable filter tailoring terahertz surface plasmon polaritons in deep-subwavelength scale, which can be further exploited for the design of ultra-compact THz plasmonic devices with dynamical tunability. Our results may also provide potential applications in optical filtering.

Abstract-Dirac semimetals based tunable narrowband absorber at terahertz frequencies

Gui-Dong Liu, Xiang Zhai, Hai-Yu Meng, Qi Lin, Yu Huang, Chu-Jun Zhao, and Ling-Ling Wang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-9-11471

In this paper, a bulk Dirac semimetals (BDSs) based tunable narrowband absorber at terahertz frequencies is proposed and it has the attractive property of being polarization-independent at normal incidence because of its 90° rotational symmetry. Numerical results show that the absorption bandwidth is about 1.469e-2 THz and the total quality factor Q, defined as Q = f0/Δf, reaches about 94.6, which can be attributed to the low power loss of the guided mode resonance in the dielectric layer. The simulation results are analyzed with coupled mode theory. Interestingly, on the premise of maintaining the absorbance at a level greater than 0.95, the absorption frequency can be tuned from 1.381 to 1.395 THz by varying the Fermi energy of BDSs from 50 to 80 meV. Our results may also provide potential applications in optical filter and bio-chemical sensing.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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

Ben-Xin Wang,  Wei-Qing Huang, Ling-Ling Wang

http://pubs.rsc.org/en/content/articlelanding/2017/ra/c7ra08413g#!divAbstract

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.

Abstract-A Simple Design of a Multi-Band Terahertz Metamaterial Absorber Based on Periodic Square Metallic Layer with T-Shaped Gap

Hai-Yu Meng,  Ling-Ling Wang, Xiang Zhai, Gui-Dong Liu, Sheng-Xuan Xia

http://link.springer.com/article/10.1007%2Fs11468-017-0509-1

We present a multi-band terahertz absorber formed by periodic square metallic ribbon with T-shaped gap and a metallic ground plane separated by a dielectric layer. It is demonstrated that absorption spectra of the proposed structure consist of four absorption peaks located at 1.12, 2.49, 3.45, and 3.91 THz with high absorption coefficients of 98.0, 98.9, 98.7, and 99.6%, respectively. It is demonstrated that the proposed absorber has the tunability from single-band to broadband by changing the length of square metallic ribbon and we can also select or tune the frequencies which we want to use by changing polarization angles. Importantly, the quality factor Q at 3.91 THz is 30.1, which is 5.6 times higher than that of 1.12 THz. These results indicate that the proposed absorber has a promising potential for devices, such as detection, sensing, and imaging.

Abstract-Six-band terahertz metamaterial absorber based on the combination of multiple-order responses of metallic patches in a dual-layer stacked resonance structure

Ben-Xin Wang, Gui-Zhen Wang, Tian Sang, Ling-Ling Wang,

http://www.nature.com/articles/srep41373

This paper reports on a numerical study of the six-band metamaterial absorber composed of two alternating stack of metallic-dielectric layers on top of a continuous metallic plane. Six obvious resonance peaks with high absorption performance (average larger than 99.37%) are realized. The first, third, fifth, and the second, fourth, sixth resonance absorption bands are attributed to the multiple-order responses (i.e., the 1-, 3- and 5-order responses) of the bottom- and top-layer of the structure, respectively, and thus the absorption mechanism of six-band absorber is due to the combination of two sets of the multiple-order resonances of these two layers. Besides, the size changes of the metallic layers have the ability to tune the frequencies of the six-band absorber. Employing the results, we also present a six-band polarization tunable absorber through varying the sizes of the structure in two orthogonal polarization directions. Moreover, nine-band terahertz absorber can be achieved by using a three-layer stacked structure. Simulation results indicate that the absorber possesses nine distinct resonance bands, and average absorptivities of them are larger than 94.03%. The six-band or nine-band absorbers obtained here have potential applications in many optoelectronic and engineering technology areas.

Abstract-Frequency tunable metamaterial absorber at deep-subwavelength scale

Ben-Xin Wang, Xiang Zhai, Gui-Zhen Wang, Wei-Qing Huang, and Ling-Ling Wang  »View Author Affiliations

http://www.opticsinfobase.org/ome/abstract.cfm?uri=ome-5-2-227

Optical Materials Express, Vol. 5, Issue 2, pp. 227-235 (2015)

View Full Text Article

Enhanced HTML    Acrobat PDF (2582 KB)

Metamaterial-based absorbers utilize the intrinsic loss, with the aid of appropriate structure design, to achieve near unity absorption at a certain frequency. The frequency of the reported absorbers is usually fixed and operates over a limited bandwidth, which greatly hampers their practical applications. Active or dynamic control over their resonance frequency is urgently necessary. Herein, we theoretically present a novel frequency tunable terahertz metamaterial absorber formed by a square metallic patch and a ground plane separated by a strontium titanate dielectric layer. Up to 80.2% frequency tuning is obtained by changing the temperature of the absorber, and there is very little variation in the strength of the absorption. The frequency shift is attributed to the temperature-dependent refractive index of the dielectric layer. Furthermore, the ratio between the lattice period and the resonance wavelength is close to 1/36 at 0.111 THz, which is smaller than the previously reported results. The proposed absorber has potential applications in detection, sensors, and selective thermal emitters.

© 2014 Optical Society of America

Abstract-Frequency Continuous Tunable Terahertz Metamaterial Absorber

Ben-Xin Wang, Ling-Ling Wang, Gui-Zhen Wang, Wei-Qing Huang, Xiao-Fei Li, andXiang Zhai 

Journal of Lightwave Technology, Vol. 32, Issue 6, pp. 1183-1189 (2014)

http://www.opticsinfobase.org/jlt/abstract.cfm?uri=jlt-32-6-1183

Metamaterial-based perfect absorbers utilize the intrinsic loss, with the aid of appropriate structural design (completely suppress transmission and reflection), to achieve near unity absorption at a certain frequency. The frequency of the reported absorbers is usually fixed and operates over a limited bandwidth, which greatly hampers their practical applications. Active or dynamic control over their resonance frequency is urgently necessary. Herein, we propose a novel approach for efficient tuning of the frequency of the absorber by shifting the movable part of the composite structure composed of the fixed and movable parts. The concept is rather general and applicable to various absorbers as long as the sandwich structure design is valid. The demonstrated continuous tuning of metamaterial absorber can find practical applications in detection, imaging, spectroscopy and selective thermal emitters.

© 2014 IEEE