Large-Area Arrays of Quasi-3D Au Nanostructures for Polarization-Selective Mid-Infrared Metasurfaces

Metasurfaces are two-dimensional patterns that are used to manipulate the propagation of light by controlling the resultant transmittance, reflectance, or absorption at specific wavelengths. Metasurfaces are typically composed of metallic or dielectric components arranged in single or multiple layers and with sizes significantly less than the wavelength of incident light. While considerable advances have been made in the design of these surfaces, there are significant challenges with high-throughput parallel fabrication over large areas which limits their applicability. Here, we demonstrate the design and characterization of mid-IR metasurfaces fabricated using a combination of photo and nanoimprint lithography (NIL). We fabricate arrays over millimeter scales with a variety of 3D nanoscale designs including asymmetric disjointed shapes and symmetric accordion-like shapes with widths of 400-600 nm, thicknesses of 30-50 nm, and lengths of 5-6 mu m. We characterize the mid-IR optical response of these metasurfaces in reflection using Fourier transform infrared (FTIR) microscopy, and simulate the spectral response using finite element method (FEM) calculations with good agreement between simulations and experiments. Also, we demonstrate that the metasurfaces exhibit characteristic and significantly different plasmonic resonance modes based on the polarization of the incoming light. Our large-area fabrication methodology allows cost-effective manufacturing of large-area metasurfaces with 3D micro- and nanoelements for scalable photonic and plasmonic devices with significant tunability in geometry and optical characteristics.