Reconfigurable plasmonic nanoslits and tuneable Pancharatnam-Berry geometric phase based on electromechanical nano-kirigami [Invited]

Reconfigurable three-dimensional (3D) nanostructures possess additional spatial freedom and rich physical characteristics compared with their two-dimensional (2D) counterparts. Here we demonstrate a facile and automated nano-kirigami method to create the 3D deformed spiral metasurfaces, which can flexibly manipulate optical waves by simply applying external voltages. Through etching Archimedean spirals into Au/SiO2/Si layer, multi-order localized surface plasmon resonances are excited within the spiral nanoslits and are dynamically tuned by floating the nanopatterns and employing the electrostatic forces, which induces a reflection modulation contrast as high as 189%. The 2D-to-3D transformation induces a strong modification of the optical chirality in both aspects of spatial distributions and strength. Importantly, the Pancharatnam-Berry (PB) geometric phase can be carefully designed and dynamically broken in the 2π range by rotating the direction of the spiral units, which results in the dynamic construction and erasing of metasurface holograms. The proposed scheme of tuning plasmonic nanoslits and breaking PB geometric phase by employing the electromechanical deformation provides a new degree of freedom for reconfigurable photonic systems, as well as dynamic applications in quasi-flat optical platforms.