Abstract-A broadband and switchable VO2-based perfect absorber at the THz frequency

Yi Zhao, Qiuping Huang, Honglei Cai, Xiaoxia Lin, Yalin Lu,



https://www.sciencedirect.com/science/article/abs/pii/S0030401818304772

We demonstrate a broadband and switchable THz metamaterial absorber by utilizing the phase transition of VO2, which is a stacked structure composed of VO2 periodic array, dielectric layer, VO${}_2$ film, Au periodic array, dielectric layer and Au reflective layer, respectively. The absorption band from 0.76 THz to 0.86 THz at room temperature can be changed into the absorption band from 1.12 THz to 1.25 THz when temperature increases above the phase change temperature of VO2, with the absorptivity in both bands over 90%. Furthermore, the effective medium theory is introduced to explain the perfect absorption mechanism. Such absorber can work well over a wide range of incidence around 40°. Thickness of the absorber is only about one twentieth of the working wavelength. The proposed structure can be applied to absorbers working at other frequencies.

Abstract-Terahertz Broadband Low-Reflection Metasurface by Controlling Phase Distributions

1. Di Sha Dong¹, 
2. Jing Yang², 
3. Qiang Cheng^1,*, 
4. Jie Zhao¹, 
5. Li Hua Gao¹, 
6. Shao Jie Ma³, 
7. Shuo Liu¹, 
8. Hai Bin Chen¹, 
9. Qiong He³,
10. Wei Wei Liu², 
11. Zheyu Fang⁴, 
12. Lei Zhou³and
13. Tie Jun Cui^1,*
14. Article first published online: 5 JUN 2015

DOI: 10.1002/adom.201500156

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

http://onlinelibrary.wiley.com/doi/10.1002/adom.201500156/abstract

Recently, reflectionless or low-reflection surfaces made of subwavelength structures have been of broad interest in practical engineering. Here, a single-layer terahertz metasurface is proposed to produce ultralow reflections across a broad-frequency spectrum and wide incidence angles by controlling the reflection phases of subwavelength structures. To enable full control of the phase range in a continuous band, a combination of two different subwavelength elements are employed, both of which exhibit weak interactions with the incident terahertz waves, thereby showing high local reflectivities near the operating frequency. An optimization method is utilized to determine the array pattern with the minimum overall reflections under the illumination of plane waves. Both numerical simulations and experimental results demonstrate ultralow reflections of terahertz waves by the metasurface over a broad frequency band and wide incidence angles. By using the proposed metasurface, the far-field scattering patterns of metallic objects can be efficiently controlled, which opens up a new route for low-reflection surface designs in the terahertz spectrum.

Abstract-Broadband and wide angle infrared wire-grid polarizer

Ming Dai,1 Weiwei Wan,1 Xueyi Zhu,1 Baosheng Song,1 Xiaoping Liu,1 Minghui Lu,1,* Bo Cui,2 and Yanfeng Chen1
1 National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China 2 Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L3G1, Canada * luminghui@nju.edu.cn
https://www.osapublishing.org/view_article.cfm?gotourl=https%3A%2F%2Fwww%2Eosapublishing%2Eorg%2FDirectPDFAccess%2F520CC20E-EC6C-2859-13E7C5F13ED981BC_320037%2Foe-23-12-15390%2Epdf%3Fda%3D1%26id%3D320037%26seq%3D0%26mobile%3Dno&org=

Abstract: An infrared polarizer consisting of metal-insulator-metal (MIM) gratings is designed with transmittance exceeding 85% and polarization extinction ratio (ER) higher than 70 dB in the wavelength range from 1.5 to 8 μm. Moreover, the polarizer retains excellent performance even when the incident angle increases to as large as 80°. The MIM gratings support magnetic polariton (MP) in the near-infrared regime and operate nonresonantly in the mid-infrared regime, both of which result in the advantages of high extinction ratio, broadband, and wide angle. The proposed structure can find applications in polarizer, beam-splitter, filter, and isolator in the infrared range.
©2015 Optical Society of America

Abstract-Optimizing Broadband Terahertz Modulation with Hybrid Graphene/Metasurface Structures

Sufei Shi , Bo Zeng , Huiling Han , Xiaoping Hong, Hsin-Zon Tsai , Han Sae Jung , Alex Zettl ,Michael F. Crommie , and Feng Wang

Nano Lett., Just Accepted Manuscript

DOI: 10.1021/nl503670d

Publication Date (Web): December 5, 2014

Copyright © 2014 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/nl503670d

We demonstrate efficient terahertz (THz) modulation by coupling graphene strongly with a broadband THz metasurface device. This THz metasurface, made of periodic gold slit arrays, shows near unity broadband transmission that arises from coherent radiation of the enhanced local-field in the slits. Utilizing graphene as an active load with tunable conductivity, we can significantly modify the local-field enhancement and strongly modulate the THz wave transmission. This hybrid device also provides a new platform for possible nonlinear THz spectroscopy study of graphene