MEMS-Driven Reconfigurable Metamaterial Waveplate at Terahertz Frequencies*

Dynamic polarization control of light is essential for numerous applications ranging from imaging to materials characterization. We present a reconfigurable terahertz metamaterial quarter-waveplate consisting of microelectromechanical systems (MEMS) cantilever actuators. The anisotropic response of the metamaterial enables polarization conversion of the transmitted waves. Specifically, electromechanical actuation of the cantilevers provides polarization selective control of the resonance frequency, enabling real-time tuning of the polarization state of the transmitted light. The polarization tunable metamaterial has been fabricated using surface micromachining and characterized using terahertz time domain spectroscopy. We obtained a ~230 GHz frequency shift of the resonance mode, modulating the transmitted wave from pure circular polarization to linear polarization at 0.8 THz with 50% amplitude variations. This work informs possibilities for real-time control of electromagnetic waves using engineered dynamic metamaterials.