Geometrical tradeoffs in graphene-based deeply-scaled electrically reconfigurable metasurfaces.

Sara Arezoomandan,Berardi Sensale-Rodriguez

doi:10.1038/srep08834

Abstract

In this work we study the terahertz light propagation through deeply-scaled graphene-based reconfigurable metasurfaces, i.e. metasurfaces with unit-cell dimensions much smaller than the terahertz wavelength. These metasurfaces are analyzed as phase modulators for constructing reconfigurable phase gradients along an optical interface for the purpose of beam shaping. Two types of deeply-scaled metacell geometries are analyzed and compared, which consist of: (i) multi split ring resonators, and (ii) multi spiral resonators. Two figures of merit, related to: (a) the loss and (b) the degree of reconfigurability achievable by such metamaterials -when applied in beam shaping applications-, are introduced and discussed. Simulations of these two types of deep-subwavelength geometries, when changing the metal coverage-fraction, show that there is an optimal coverage-fraction that gives the best tradeoff in terms of loss versus degree of reconfigurability. For both types of geometries the best tradeoff occurs when the area covered by the metallic region is around 40% of the metacell total area. From this point of view, reconfigurable deeply-scaled metamaterials can indeed provide a superior performance for beam shaping applications when compared to not deeply-scaled ones; however, counterintuitively, employing very highly-packed structures might not be beneficial for such applications.

Highlights

Correspondence and requests for materials should be addressed to Geometrical tradeoffs in graphene-based deeply-scaled electrically reconfigurable metasurfaces
From this point of view, reconfigurable deeply-scaled metamaterials can provide a superior performance for beam shaping applications when compared to not deeply-scaled ones; counterintuitively, employing very highly-packed structures might not be beneficial for such applications
Reconfigurable terahertz metamaterials[2] were shown capable of modulating the phase of an arbitrary terahertz beam[3]; these metamaterial phase modulators can be employed to construct arbitrary phase gradients in an optical interface, which is of special interest for terahertz beam-shaping applications

Summary

Introduction

Correspondence and requests for materials should be addressed to Geometrical tradeoffs in graphene-based deeply-scaled electrically reconfigurable metasurfaces. In this work we study the terahertz light propagation through deeply-scaled graphene-based reconfigurable metasurfaces, i.e. metasurfaces with unit-cell dimensions much smaller than the terahertz wavelength These metasurfaces are analyzed as phase modulators for constructing reconfigurable phase gradients along an optical interface for the purpose of beam shaping. Two figures of merit, related to: (a) the loss and (b) the degree of reconfigurability achievable by such metamaterials -when applied in beam shaping applications-, are introduced and discussed Simulations of these two types of deep-subwavelength geometries, when changing the metal coverage-fraction, show that there is an optimal coverage-fraction that gives the best tradeoff in terms of loss versus degree of reconfigurability. When a phase gradient is placed in the interface between two media of refractive index nt and ni, Snell’s law of transmission should be rephrased as the generalized law of reflection and refraction[4]: sinðht

Methods

Results

Conclusion