Abstract-Design and performance of a terahertz absorber based on patterned graphene

Yannan Jiang, Huai De Zhang, Jiao Wang, Chao Ning Gao, Jia Wang, and Wei Ping Cao

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-17-4296

Modern terahertz (THz) technology offers the advantage of enhanced target detection ability with high spatial and temporal resolutions in the THz band, which makes it a formidable threat to stealth targets. Consequently, THz absorbers have outstanding potential as an electromagnetic countermeasure. In this Letter, we design, fabricate, and characterize a THz absorber based on patterned graphene. We present the transfer, photolithography, and etching processes involved in graphene patterning, as well as the experimental measurements of the fabricated absorber. Our simulations show that with an increase in the Fermi energy, the performance of the designed absorber gradually improves and, finally, decreases slightly. Further, the absorption bandwidth first broadens and then narrows slightly. The effective bandwidth with absorption ≥90%$\ge 90\%$ ranges from 1.54 to 2.23 THz, with the relative bandwidth (RBW) reaching about 36.6%. Although the measured RBW (from ∼12%$\sim 12\%$ to ∼14%$\sim 14\%$ and then to ∼8%$\sim 8\%$) slightly deviates from the simulated one, the position of the resonant frequency is well matched between theory and experiment. Moreover, we illuminate the absorption mechanism using the theory of destructive interference. This Letter can significantly contribute to the design, manufacture, and application of patterned graphene-based THz absorbers.

© 2018 Optical Society of America

Abstract-Terahertz Imaging Progress at Capital Normal University

Guozhong Zhao, Jiayi Yu, Yashang Li, Jia Wang,

http://www.sciencepublishinggroup.com/journal/paperinfo?journalid=302&doi=10.11648/j.ijass.20170505.12

The progress on terahertz imaging at Capital Normal University in Beijing is presented. Our works on Terahertz Imaging include the active and passive imaging. For the active terahertz imaging, the pulse and continue wave terahertz imaging are studied, respectively. The active terahertz pulse imaging is based on the terahertz time-domain spectroscopy (THz-TDS). A practical focus-plane imaging system is built up based on the THz-TDS with the probe-beam-expanded electro-optical sampling and an infrared CCD imaging. The active terahertz continuous wave imaging is based on a CO₂-laser-pumped terahertz coherent source and an uncooled bolometer array of terahertz camera. The active terahertz polarization imaging and wave front imaging is developed. For the passive terahertz imaging, the low frequency of radiometers are used to detect the point-to-point beam-scanned terahertz signal by the optical focusing and scanning system so that the passive THz imaging is realized for the security inspection of human body. The related components and image processing methods are studied and used for the improvement of imaging speed and resolution. The research on THz imaging technology at Capital Normal University is opening up a potential application in the field of non-destructive testing and security inspection for the terahertz technology.

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This article is an open access article distributed under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract-New progress of active and passive terahertz imaging

Guozhong Zhao, Jia Wang, Jiayi Yu

Capital Normal Univ. (China)

Yanchun Shen

Capital Normal Univ. (China)

Proc. SPIE 10030, Infrared, Millimeter-Wave, and Terahertz Technologies IV, 100300Q (December 8, 2016); doi:10.1117/12.2246784

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2593072


The progress on terahertz imaging at Capital Normal University in Beijing is presented. Our works on Terahertz Imaging include the active and passive imaging. For the active terahertz imaging, the pulse and continue wave terahertz imaging are studied, respectively. The active terahertz pulse imaging is based on the terahertz time-domain spectroscopy with the probe-beam-expanded femtosecond pulse laser and an infrared CCD detection.
 The active terahertz continuous wave imaging is based on a CO2-laser-pumped terahertz coherent source and a NEC terahertz camera. The active terahertz polarization imaging is studied. For the passive terahertz imaging, the low frequency radiometers are used to detect the beam-scanned terahertz signal by the point-to-point scanning. The related components and image processing methods are developed and used for the improvement of imaging speed and resolution.
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