Nanooptics

Metasurfaces comprising three-dimensional (3D) chiral structures have shown great potential in chiroptical applications such as ultra-compact chiral optical components and sensing. So far, the main challenges lie in the nanofabrication and the limited operational bandwidth. Here, an effective one-step nanofabrication method to create a 3D chiral metasurface with broadband chiroptical properties is demonstrated. A focused ion beam is used to cut and stretch nano-wires into 3D Archimedean spirals from stacked metal/dielectric films. The 3D Archimedean spiral is a self-similar structure to circularly polarized light (CPL). This makes it capable of exhibiting a broadband chiroptical response and automatic field localization from 2μm to 8μm. The effective yet straightforward fabrication strategy and the superior broadband chiroptical response of our 3D metasurface facilitate applications in broadband chiral optics and sensing.