Abstract-Reconfigurable MEMS Fano metasurfaces with multiple-input–output states for logic operations at terahertz frequencies

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

https://www.nature.com/articles/s41467-018-06360-5

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.

Abstract-Optical Anapole Metamaterial

Pin Chieh Wu, Chun Yen Liao, Vassili Savinov, Tsung Lin Chung, Wei Ting Chen, Yao-Wei Huang, Pei Ru Wu, Yi-Hao Chen, Ai-Qun Liu, Nikolay I. Zheludev,  Din Ping, Tsai

http://pubs.acs.org/doi/abs/10.1021/acsnano.7b08828

The toroidal dipole is a localized electromagnetic excitation independent from the familiar magnetic and electric dipoles. It corresponds to currents flowing along minor loops of a torus. Interference of radiating induced toroidal and electric dipoles leads to anapole, a non-radiating charge-current configuration. Interactions of induced toroidal dipoles with electromagnetic waves have recently been observed in artificial media at microwave, terahertz and optical frequencies. Here, we demonstrate a quasi-planar plasmonic metamaterial – a combination of dumbbell aperture and vertical split-ring resonator - that exhibits transverse toroidal moment and resonant anapole behavior in the optical part of the spectrum upon excitation with a normally incident electromagnetic wave. Our results prove experimentally that toroidal modes and anapole modes can provide distinct and physically significant contributions to the absorption and dispersion of slabs of matter in the optical part of the spectrum in conventional transmission and reflection experiments.

Abstract-Sharp Toroidal Resonances in Planar Terahertz Metasurfaces

http://onlinelibrary.wiley.com/doi/10.1002/adma.201601611/abstract

A toroidal dipole in metasurfaces provides an alternate approach for the excitation of high-Qresonances. In contrast to conventional multipoles, toroidal dipole interaction strength depends on the time derivative of the surrounding electric field. A characteristic feature of a toroidal dipole is tightly confined loops of oscillating magnetic field that curl around the fictitious arrow of a toroidal dipole vector.