Abstract-Electromechanically tunable metasurface transmission waveplate at terahertz frequencies

Xiaoguang Zhao, Jacob Schalch, Jingdi Zhang, Huseyin R. Seren, Guangwu Duan, Richard D. Averitt, and Xin Zhang

https://www.osapublishing.org/optica/abstract.cfm?uri=optica-5-3-303

Dynamic polarization control of light is essential for numerous applications ranging from enhanced imaging to material characterization and identification. We present a reconfigurable terahertz metasurface quarter-wave plate consisting of electromechanically actuated microcantilever arrays. Our anisotropic metasurface enables tunable polarization conversion through cantilever actuation. Specifically, voltage-based actuation provides mode-selective control of the resonance frequency, enabling real-time tuning of the polarization state of the transmitted light. The polarization tunable metasurface has been fabricated using surface micromachining and characterized using terahertz time domain spectroscopy. We observe a ∼230  GHz$\sim 230\mathrm{GHz}$ cantilever actuated frequency shift of the resonance mode, sufficient to modulate the transmitted wave from pure circular polarization to linear polarization. Our CMOS-compatible tunable quarter-wave plate enriches the library of terahertz optical components, thereby facilitating practical applications of terahertz technologies.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Structural Control of Metamaterial Oscillator Strength and Electric Field Enhancement at Terahertz Frequencies

George R. Keiser, Huseyin R. Seren, Andrew C. Strikwerda, Xin Zhang, Richard D. Averitt

(Submitted on 4 Jun 2014)

The design of artificial nonlinear materials requires control over the internal resonant charge densities and local electric field distributions. We present a MM design with a structurally controllable oscillator strength and local electric field enhancement at terahertz frequencies. The MM consists of a split ring resonator (SRR) array stacked above an array of nonresonant closed conducting rings. An in-plane, lateral shift of a half unit cell between the SRR and closed ring arrays results in a decrease of the MM oscillator strength by a factor of 4 and a 40% change in the amplitude of the resonant electric field enhancement in the SRR capacitive gap. We use terahertz time-domain spectroscopy and numerical simulations to confirm our results and we propose a qualitative inductive coupling model to explain the observed electromagnetic reponse.