Abstract-Tunable broadband terahertz polarizer using graphene-metal hybrid metasurface

K. Meng, S. J. Park, L. H. Li, D. R. Bacon, L. Chen, K. Chae, J. Y. Park, A. D. Burnett, E. H. Linfield, A. G. Davies, and J. E. Cunningham

 (a) Schematic diagram of the graphene-metal hybrid wire grid structure. Upper figure: cross-section of the array, lower figure: top view of the array. (b) Schematic diagram of the THz transmission experiment: the lower electrode was used for applying gate voltage and the upper two electrodes were connected to a source meter for measuring the conductivity (indicated by G) (c) DC conductivities of graphene in each device as a function of gate voltage. (d) SEM image of the graphene-metal hybrid wire grids with 𝛬𝑀/𝐺=30𝜇𝑚${\Lambda }_{M/G}=30\mu m$. (e) Raman spectrum of the graphene in a typical device.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-23-33768

We demonstrate an electrically tunable polarizer for terahertz (THz) frequency electromagnetic waves formed from a hybrid graphene-metal metasurface. Broadband (>3 THz) polarization-dependent modulation of THz transmission is demonstrated as a function of the graphene conductivity for various wire grid geometries, each tuned by gating using an overlaid ion gel. We show a strong enhancement of modulation (up to ∼17 times) compared to graphene wire grids in the frequency range of 0.2–2.5 THz upon introduction of the metallic elements. Theoretical calculations, considering both plasmonic coupling and Drude absorption, are in good agreement with our experimental findings.

Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Abstract-Increasing the sensitivity of terahertz split ring resonator metamaterials for dielectric sensing by localized substrate etching

K. Meng, S. J. Park, A. D. Burnett, T. Gill, C. D. Wood, M. Rosamond, L. H. Li, L. Chen, D. R. Bacon, J. R. Freeman, P. Dean, Y. H. Ahn, E. H. Linfield, A. G. Davies,  J. E. Cunningham, 

Fig. 1. (a) Schematic of THz transmission experiment for dielectric sensing using the etched metamaterials. (b) Schematic of THz metamaterials arrays with etched trenches. The periodicity of the metamaterials unit cells is indicated (c) An SEM image of the metamaterial with a trench depth of 1.74 µm. Cross-section SEM images of the metamaterials with trench depths t of (d) 1.74 µm and (e) 130 nm in the gap area.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-16-23164

We demonstrate a significant enhancement in the sensitivity of split ring resonator terahertz metamaterial dielectric sensors by the introduction of etched trenches into their inductive-capacitive gap area, both through finite element simulations and in experiments performed using terahertz time-domain spectroscopy. The enhanced sensitivity is demonstrated by observation of an increased frequency shift in response to overlaid dielectric material of thicknesses up to 18 µm deposited on to the sensor surface. We show that sensitivity to the dielectric is enhanced by a factor of up to ∼2.7 times by the incorporation of locally etched trenches with a depth of ∼3.4 µm, for example, and discuss the effect of the etching on the electrical properties of the sensors. Our experimental findings are in good agreement with simulations of the sensors obtained using finite element methods.

Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.