title: Microelectromechanical Maltese-cross metamaterial with tunable terahertz anisotropy.
abstract: Dichroic polarizers and waveplates exploiting anisotropic materials have vast applications in displays and numerous optical components, such as filters, beamsplitters and isolators. Artificial anisotropic media were recently suggested for the realization of negative refraction, cloaking, hyperlenses, and controlling luminescence. However, extending these applications into the terahertz domain is hampered by a lack of natural anisotropic media, while artificial metamaterials offer a strong engineered anisotropic response. Here we demonstrate a terahertz metamaterial with anisotropy tunable from positive to negative values. It is based on the Maltese-cross pattern, where anisotropy is induced by breaking the four-fold symmetry of the cross by displacing one of its beams. The symmetry breaking permits the excitation of a Fano mode active for one of the polarization eigenstates controlled by actuators using microelectromechanical systems. The metamaterial offers new opportunities for the development of terahertz variable waveplates, tunable filters and polarimetry.
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.
authors.forename: W M
authors.initials: WM
authors.lastname: Zhu
authors.forename: A Q
authors.initials: AQ
authors.lastname: Liu
authors.forename: T
authors.initials: T
authors.lastname: Bourouina
authors.forename: D P
authors.initials: DP
authors.lastname: Tsai
authors.forename: J H
authors.initials: JH
authors.lastname: Teng
authors.forename: X H
authors.initials: XH
authors.lastname: Zhang
authors.forename: G Q
authors.initials: GQ
authors.lastname: Lo
authors.forename: D L
authors.initials: DL
authors.lastname: Kwong
authors.forename: N I
authors.initials: NI
authors.lastname: Zheludev