Reconfigurable MEMS Fano metasurfaces with multiple-input\u2013output states for logic operations at terahertz frequencies

Manukumara Manjappa,Prakash Pitchappa,Ranjan Singh,Navab Singh,Chengkuo Lee,Nan Wang,Nikolay I Zheludev

doi:10.1038/s41467-018-06360-5

Abstract

A broad range of dynamic metasurfaces has been developed for manipulating the intensity, phase and wavefront of electromagnetic radiation from microwaves to optical frequencies. However, most of these metasurfaces operate in single-input–output state. Here, we experimentally demonstrate a reconfigurable MEMS Fano resonant metasurface possessing multiple-input–output (MIO) states that performs logic operations with two independently controlled electrical inputs and an optical readout at terahertz frequencies. The far-field behaviour of Fano resonance exhibits XOR and XNOR operations, while the near-field resonant confinement enables the NAND operation. The MIO configuration resembling hysteresis-type closed-loop behaviour is realized through inducing electromechanically tuneable out-of-plane anisotropy in the near-field coupling of constituent resonator structures. The XOR metamaterial gate possesses potential applications in cryptographically secured terahertz wireless communication networks. Furthermore, the MIO features could lay the foundation for the realization of programmable and randomly accessible metamaterials with enhanced electro-optical performance across terahertz, infrared and optical frequencies.

Highlights

A broad range of dynamic metasurfaces has been developed for manipulating the intensity, phase and wavefront of electromagnetic radiation from microwaves to optical frequencies
Scanning electron microscope (SEM) image of the fabricated MEMS Fanometasurface is shown in Fig. 1a in the coloured scale that illustrates the maximum asymmetric state of the device with SRR-1 snapped down on the substrate using voltage V1 = 35 V and SRR2 is retained in the released state of the bimorph cantilevers with
The excitation of sharp Fano resonance feature in metamaterials has been pivotal in enhancing the confinement of near-field energy in the structures to aid the strong nonlinearity and sensing applications[36]

Summary

Introduction

A broad range of dynamic metasurfaces has been developed for manipulating the intensity, phase and wavefront of electromagnetic radiation from microwaves to optical frequencies. At the terahertz (THz) and infrared frequencies, the MEMS/NEMS metasurfaces have enabled dynamic manipulation of near-field entities thereby showing an active reconfiguration of intriguing features like magnetic response[4,10], transparency[20], near-perfect absorption[21], phase engineering[22], resonance modulation[23], anisotropy[5] and THz invisibility[24]. Apart from these useful advancements, the ability to control and tailor the near-field interactions by establishing multiple controls at the unit-cell level has remained elusive. The multiple-logic operations together with the volatile and nonvolatile[32,33] regimes of MEMS actuation can enhance the digital functionalities of the device in realizing optical memory registers to encode, harvest, process and send secured information in the form of encoded/decoded optical bits at THz frequencies

Methods

Results

Conclusion