Transmissive terahertz metasurfaces with vanadium dioxide split-rings and grids for switchable asymmetric polarization manipulation

Andriy E Serebryannikov,Akhlesh Lakhtakia,Guy A E Vandenbosch,Ekmel Ozbay

doi:10.1038/s41598-022-07265-6

Andriy E Serebryannikov, Akhlesh Lakhtakia + Show 2 more

Open Access

https://doi.org/10.1038/s41598-022-07265-6

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Abstract

Metasurfaces containing arrays of thermally tunable metal-free (double-)split-ring meta-atoms and metal-free grids made of vanadium dioxide (VO_2), a phase-change material can deliver switching between (1) polarization manipulation in transmission mode as well as related asymmetric transmission and (2) other functionalities in the terahertz regime, especially when operation in the transmission mode is needed to be conserved for both phases of VO_2. As the meta-atom arrays function as arrays of metallic subwavelength resonators for the metallic phase of VO_2, but as transmissive phase screens for the insulator phase of VO_2, numerical simulations of double- and triple-array metasurfaces strongly indicate extreme scenarios of functionality switching also when the resulting structure comprises only VO_2 meta-atoms and VO_2 grids. More switching scenarios are achievable when only one meta-atom array or one grid is made of VO_2 components. They are enabled by the efficient coupling of the geometrically identical resonator arrays/grids that are made of the materials that strongly differ in terms of conductivity, i.e. Cu and VO_2 in the metallic phase.

Highlights

Metasurfaces containing arrays of thermally tunable metal-freesplit-ring meta-atoms and metal-free grids made of vanadium dioxide (VO2 ), a phase-change material can deliver switching between (1) polarization manipulation in transmission mode as well as related asymmetric transmission and (2) other functionalities in the terahertz regime, especially when operation in the transmission mode is needed to be conserved for both phases of VO2
We have proposed and numerically validated that few-layer metasurfaces comprising electrically thin metal-free meta-atoms and grids made of VO2 are capable of polarization manipulation and asymmetric transmission
We have demonstrated that the thermal transition from the M/I to the I/M phase of VO2 may result in extreme functional reconfiguration, while either conserving the transmission mode of operation or changing it for the reflection mode

Summary

Introduction

Metasurfaces containing arrays of thermally tunable metal-free (double-)split-ring meta-atoms and metal-free grids made of vanadium dioxide (VO2 ), a phase-change material can deliver switching between (1) polarization manipulation in transmission mode as well as related asymmetric transmission and (2) other functionalities in the terahertz regime, especially when operation in the transmission mode is needed to be conserved for both phases of VO2. Transition from an insulator (I) phase to a metallic (M) phase, or vice versa, under the influence of a control parameter is a general feature of many natural m aterials[2,3] that allows control of the permittivity tensor in the complex plane at a fixed frequency It has particular significance for metasurfaces with switchable functionality. It can be challenging to deposit VO2 components of the meta-atoms because of the commonplace formation of non-stochiometric vanadium oxide (i.e., VOζ , where ζ is not the ratio of two small integers)[34,35] whose thermal-tunability characteristics can differ very significantly from those of stochiometric forms (such as VO2 , V 2O3 , V 2O5 , V 4O7 , etc.)

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