TST, Vol. 9, No. 1, PP. 1-9
(Invited paper) Terahertz antireflection coating enabled by a subwavelength metallic mesh capped with a thin dielectric film
Li Huang 1*, Beibei Zeng 2, Chun-Chieh Chang 2 and Hou-Tong Chen 2*
1 Physics Department, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China
2 Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
*1 Email: lihuang2002@hit.edu.cn , *2 Email: chenht@lanl.gov
(Received August 18, 2015 )
Abstract: Metamaterials/metasurfaces have enabled unprecedented manipulation of electromagnetic waves. Here we present a new design of metasurface structure functioning as antireflection coatings. The structure consists of a subwavelength metallic mesh capped with a thin dielectric layer on top of a substrate. By tailoring the geometric parameters of the metallic mesh and the refractive index and thickness of the capping dielectric film, reflection from the substrate can be completely eliminated at a specific frequency. Compared to traditional methods such as coatings with single- or multi-layer dielectric films, the metasurface antireflection coatings are much thinner and the requirement of index matching is largely lifted. This approach is particularly suitable for antireflection coatings in the technically challenging terahertz frequency range and is also applicable in other frequency regimes.
Keywords: Metasurfaces, Antireflection coatings, Terahertz, Interference
doi: 10.11906/TST.001-009.2016.03.01
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TST, Vol. 9, No. 1, PP. 10-18
(Invited paper) Schottky diode characterization, modelling and design for THz front-ends
Tero Kiuru *
VTT Technical Research Centre of Finland, Communication systems
P.O Box 1000, FI-02044 VTT, Finland
* Email: tero.kiuru@vtt.fi
(Received August 18, 2015 )
Abstract: Efficient characterization and modelling techniques have a key role in the development of Schottky diode-based devices with state-of-the-art performance. This paper makes an effort to introduce such techniques and to provide examples of how they are used by the Schottky community. The modelling techniques covered in the paper are circuit simulator and electro-magnetic modelling. Characterization methods include current-voltage, capacitance-voltage, S-parameter, test jig-based, and thermal measurement techniques.
Keywords: Schottky diode, Modelling, Characterization, S-parameters, I-V measurements, C-V measurements, Thermal characterization
doi: 10.11906/TST.010-018.2016.03.02
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TST, Vol. 9, No. 1, PP. 19-36
(Invited paper) Terahertz imaging for security – algorithm and system realization
Chao Li 1, 2*, and GuangYou Fang 1, 2
1 The Key Laboratory of Electromagnetic Radiation and Sensing Technology, Chinese Academy of Sciences, BeiJing, China
2 Institute of Electronics, Chinese Academy of Sciences, BeiJing, China
*2 Email: cli@mail.ie.ac.cn
(Received August 18, 2015)
Abstract: Terahertz (THz) wave has unique properties due to its special position in the electromagnetic spectrum, which lies in the gap between the electronics and photonics. In recent years, imaging and sensing with EM radiation in Terahertz band has aroused considerable interests and is found to be promising for plenty of applications, such as security and safety screening, process monitoring and non-destructive materials testing. Besides being limited by the maturity of electronic components, design and realization of imaging systems at THz band with high performance is a complex issue which is dependent on variety of key parameters such as spatial resolution, sensitivity, target contrast, target identification, and so on. This paper describes and summarizes some background on THz imaging, and the recent progress on the research of THz imaging and sensing at Institute of Electronics, Chinese Academy of Sciences, both in theoretical and some system engineering aspects. The imaging scheme and reconstruction algorithm with synthesized aperture concept was extended to THz band. The relationships between the image qualities and the parameters of quasi-optical transceivers were quantitatively evaluated for the guidance of system development. Some novel THz imaging concepts based on sparse information were also introduced, such as the single frequency adaptive focusing with minimum-entropy (ME) method, and THz surface layer reconstruction with sparse random step frequency. Based on the combination of the synthesized aperture concept, the novel beam scanning method, and THz frequency modulated continuous wave (FMCW) transceiver, three-dimensional (3D) imaging radar in sub-THz band with real-time capability was developed, which has potential applications for security screen.
Keywords: Terahertz imaging, Security, Reconstruction algorithm, Synthesized aperture technique, Beam scanning
doi: 10.11906/TST.019-036.2016.03.03
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TST, Vol. 9, No. 1, PP. 37-44
(Invited paper) Manipulating polarization and light propagation using THz metamaterials
Jinhui Shi 1, 2*, Ke Wang 1, and Han Zhang 1
1 SZU-NUS Collaborative Innovation Centre for Optoelectronic Science & Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen 518060, China
2 Key Laboratory of In-Fiber Integrated Optics of Ministry of Education, College of Science, Harbin Engineering University, Harbin 150001, China
*2 Email: shijinhui@hrbeu.edu.cn
(Received August 18, 2015)
Abstract: The field of metamaterials has been developing rapidly in recent years. Chiral metamaterials and metasurfaces, as promising candidates, hold great advantages and flexibilities to manipulate the polarization state of light. In this talk, we will review THz metamaterial work in our group. We will recall experimental results of manipulating polarization properties using chiral metamaterials in the microwave range. In addition, we review an optically controlled terahertz (THz) switch to tune the state of polarization based on a bilayered chiral metamaterials. The chiral metamaterial consists of an array of perforated slits with incorporated photoactive silicon, which allows us to control dynamically cross-polarization transmission. The switch state can be efficiently controlled by external optical stimuli. The realization of cross-polarization THz switch in the chiral metamaterial has simple structure design and easy fabrication and therefore the proposed chiral metamaterial will be a promising candidate for polarization control devices.
Keywords: THz metamaterial, Metasurface, Photoconductivity, Chirality, Switching
doi: 10.11906/TST.037-044.2016.03.04
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