Large-Area Nanophotonics Fabricated by Interferometric Lithography

Large area (several cm2) mid- and near-infrared metamaterial samples including analogs to split-ring resonators and negative-index materials are fabricated using interferometric lithography and standard integrated circuit fabrication techniques. The split-ring resonators are vertical structures with the smallest dimensions defined by deposition rather than by lithography. The negative index material is an Au-Al2O3-Au stack structure perforated with a 2D hole pattern. Both the amplitude and phase of the transmission and reflectivity are measured with phase-mask, zero-path-length difference, interferometric techniques and the refractive index is deduced by inverting these measurements. A rigorous coupled wave analysis (RCWA) is in excellent agreement with the measurement. Improvements in the original structure to provide a lower loss and an improved transmission for the structure are presented. Prospects for continued reduction in the loss and an improved figure of merit, [|Re(n)|/Im(n)], are discussed. Interferometric lithography provides an inexpensive, facile, large-area technology for the fabrication of visible/infrared metamaterials with a 2D array patterning capability extending to as small as ~20-nm features.