Three-dimensional metamaterials: From split ring resonator to toroidal metamolecule

Split ring resonator (SRR) has attracted wide attentions since the discovery of negative refraction in 2002. Here, we designed and fabricated vertical SRR (VSRR) arrays and toroidal metamolecule by using double exposure e-beam lithography with precise alignment technique, and their resonance behaviors are subsequently studied in optical region. The fundamental resonance properties of VSRR are studied as well as the plasmon coupling in a VSRR dimer structure by changing the gap distance between SRRs. In addition, we proposed a three-dimensional toroidal structure composed a VSRR with a dumbbell structure that supported a toroidal resonance under normal incidence with broadband working frequency. Such toroidal metamaterial confines effectively the electric as well as magnetic energy paving a way for promising applications in the field of plasmonics, such as integrated 3D plasmonic metamaterials, plasmonic biosensor and lasing spaser.