Abstract-Tunable terahertz fishnet metamaterials based on thin nematic liquid crystal layers for fast switching

• Dimitrios C. Zografopoulos
•  & Romeo Beccherelli

http://www.nature.com/articles/srep13137

The electrically tunable properties of liquid-crystal fishnet metamaterials are theoretically investigated in the terahertz spectrum. A nematic liquid crystal layer is introduced between two fishnet metallic structures, forming a voltage-controlled metamaterial cavity. Tuning of the nematic molecular orientation is shown to shift the magnetic resonance frequency of the metamaterial and its overall electromagnetic response. A shift higher than 150 GHz is predicted for common dielectric and liquid crystalline materials used in terahertz technology and for low applied voltage values. Owing to the few micron-thick liquid crystal cell, the response speed of the tunable metamaterial is calculated as orders of magnitude faster than in demonstrated liquid-crystal based non-resonant terahertz components. Such tunable metamaterial elements are proposed for the advanced control of electromagnetic wave propagation in terahertz applications

Abstract-Exploiting the dispersion of the double-negative-index fishnet metamaterial to create a broadband low-profile metallic lens

Exploiting the dispersion of the double-negative-index fishnet metamaterial to create a broadband low-profile metallic lens B. Orazbayev, V. Pacheco-Peña, M. Beruete, and M. Navarro-Cía  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-23-7-8555

Optics Express, Vol. 23, Issue 7, pp. 8555-8564 (2015)
http://dx.doi.org/10.1364/OE.23.008555

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Metamaterial lenses with close values of permittivity and permeability usually display low reflection losses at the expense of narrow single frequency operation. Here, a broadband low-profile lens is designed by exploiting the dispersion of a fishnet metamaterial together with the zoning technique. The lens operates in a broadband regime from 54 GHz to 58 GHz, representing a fractional bandwidth ~7%, and outperforms Silicon lenses between 54 and 55.5 GHz. This broadband operation is demonstrated by a systematic analysis comprising Huygens-Fresnel analytical method, full-wave numerical simulations and experimental measurements at millimeter waves. For demonstrative purposes, a detailed study of the lens operation at two frequencies is done for the most important lens parameters (focal length, depth of focus, resolution, radiation diagram). Experimental results demonstrate diffraction-limited ~0.5λ transverse resolution, in agreement with analytical and numerical calculations. In a lens antenna configuration, a directivity as high as 16.6 dBi is achieved. The different focal lengths implemented into a single lens could be potentially used for realizing the front end of a non-mechanical zoom millimeter-wave imaging system.

© 2015 Optical Society of America

Abstract-Tunable terahertz fishnet metamaterial

http://apl.aip.org/resource/1/applab/v102/i15/p151903_s1?isAuthorized=no
Cheng-Ling Chang, Wei-Chih Wang, Hong-Ren Lin, Feng Ju Hsieh, Yue-Bun Pun, Chi-Hou Chan

This paper describes and demonstrates a terahertz (THz) frequency tunable fishnet metamaterial (TFMM) using an electrically controlled polymer dispersed liquid crystal (PDLC) matrix. In contrast to other PDLC-based devices, the TFMM employs a novel method for encapsulating PDLC using a thin (1.5 μm) polyimide “skin layer” to form a uniform surface for metal electrodes while minimizing the Fabry-Perot effect of the skin layer on the TFMM measurements. The tunability was verified by measuring the frequency shift in the reflection coefficient (0.01 THz), with an observed minimum negative refractive index of −15 at 0.55 THz.

© 2013 AIP Publishing LLC