In the past 4th Scientific Meeting of BNC-b Students Mayte Gómez, one of our PhD students of the Nanopto group, was awarded with the best poster for her contribution entitled ‘Tunable index metamaterials made by bottom-up approaches ‘.
Despite the exciting electromagnetic properties that negative-index metamaterials exhibit, their implementation in nowadays technology is limited by the traditionally used top-down techniques, which involve costly and low-throughput processes. As alternative, we present an inexpensive and up scalable route to fabricate double
fishnet metamaterials over centimetre-sized areas that relies on the combination of colloidal lithography and metallic electrodeposition. Our design is based on a hexagonally ordered monolayer of polystyrene beads used as template for the infiltration of two symmetric gold layers separated by an air gap. The obtained structures have been characterized by vis-NIR microspectroscopy, exhibiting extinction resonances in the near-infrared range. The good agreement between the optical measurements and the finite-difference time-domain (FDTD) simulations attests the success of our fabrication process. The effective optical properties, retrieved from the calculations by the homogenization method, demonstrate that we are experimentally able to tailor the refractive index from positive to negative and zero values by the proper choice of the particles diameter and the gap width between the metallic layers. In particular, negative metamaterials with a refractive index of -1 in the near-infrared and working over a 100 nm wide spectral range have been successfully fabricated. Our results open the door to a new approach for the low-cost fabrication of negative-index metamaterials.