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-Metamaterials: Active Control of Electromagnetically Induced Transparency Analog in Terahertz MEMS Metamaterial

1. Prakash Pitchappa^1,2,4, 
2. Manukumara Manjappa³, 
3. Chong Pei Ho^1,3,4, 
4. Ranjan Singh³, 
5. Navab Singh⁴ and
6. Chengkuo Lee^1,2,*

http://onlinelibrary.wiley.com/doi/10.1002/adom.201670021/abstract
Article first published online: 20 APR 2016

DOI: 10.1002/adom.201670021

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Issue 

Coupled mode resonators provide an access route for the realization of electromagnetically induced transparency (EIT) analogues in the terahertz spectral region. On page 541, C. Lee and co-workers experimentally realize a microelectromechanical system (MEMS)-based metamaterial to provide both active modulation of EIT intensity and spectral tuning of the EIT peak. This is achieved through selective reconfiguration of bright and dark mode resonators, respectively. An order of magnitude change in delay-bandwidth product is achieved.

Abstract-Microelectromechanically tunable multiband metamaterial with preserved isotropy

Prakash Pitchappa,

Chong Pei Ho,

You Qian,

Lokesh Dhakar,

Navab Singh

& Chengkuo Lee

http://www.nature.com/srep/2015/150626/srep11678/full/srep11678.html
We experimentally demonstrate a micromachined reconfigurable metamaterial with polarization independent characteristics for multiple resonances in terahertz spectral region. The metamaterial unit cell consists of eight out-of-plane deformable microcantilevers placed at each corner of an octagon ring. The octagon shaped unit cell geometry provides the desired rotational symmetry, while the out-of-plane movable cantilevers preserves the symmetry at different configurations of the metamaterial. The metamaterial is shown to provide polarization independent response for both electrical inductive-capacitive (eLC) resonance and dipolar resonance at all states of actuation. The proposed metamaterial has a switching range of 0.16 THz and 0.37 THz and a transmission intensity change of more than 0.2 and 0.7 for the eLC and dipolar resonances, respectively for both TE and TM modes. Further optimization of the metal layer thickness, provides an improvement of up to 80% modulation at 0.57 THz. The simultaneously tunable dual band isotropic metamaterial will enable the realization of high performance electro-optic devices that would facilitate numerous terahertz applications such as compressive terahertz imaging, miniaturized terahertz spectroscopy and next generation high speed wireless communication possible in the near future.