Fabrication of optical negative-index metamaterials: Recent advances and outlook

A status report on optical negative-index-metamaterial fabrication is given. The advantages, drawbacks and challenges of different fabrication techniques including electron-beam lithography (EBL), focused-ion beam (FIB) milling, interference lithography (IL) and nanoimprint lithography (NIL) and direct laser writing are outlined. Since the possibility of creating a truly three-dimensional (3D) metamaterial is critical for real-life applications and the future of this research area, the recent developments on large-scale, multiple-functional-layer metamaterials are discussed in detail, and alternative methods for 3D fabrication of complex structures are mentioned. Throughout the report, main breakthroughs in fabrication of optical negative-index metamaterials are described, as well as challenges facing future manufacturing of optical metamaterials.