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

Dimitrios C Zografopoulos,Romeo Beccherelli

doi:10.1038/srep13137

Dimitrios C Zografopoulos, Romeo Beccherelli

Open Access

https://doi.org/10.1038/srep13137

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Abstract

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.

Highlights

Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM), Roma 00133, Italy
In the THz spectrum, the infiltration of metamaterial resonant structures with nematic materials offers a striking advantage, namely the reduction of the LC layer thickness to few microns, owing to their large interaction with the resonant EM field[26,34,36,37]. Such dimensions are compatible with standard LC technology used in the photonics or display industry, they eliminate alignment issues that may appear in thicker non-resonant cells far employed in THz phase modulators and filters[38,39], require low driving voltages, and, most importantly, allow for orders of magnitude faster switching speeds, since the response times of nematic LC cells scale with the square of their thickness
Apart from providing the electromagnetic resonances that lead to negative index metamaterials (NIM) properties, the metallic layers serve as the electrodes for the application of the control voltage