Electromagnetically induced transparency (EIT)-like effects in silver, gold, and aluminum metamaterials consisting of dipole resonators and quadrupole resonators were demonstrated at visible wavelengths. Optical characteristics of the metamaterials could be controlled by the gap distance between the two resonators. EIT-like effects were observed at wavelengths between 603 and 789 nm, 654 and 834 nm, and 462 and 693 nm for the silver, gold, and aluminum EIT metamaterials, respectively. At wavelengths longer than around 650 nm, the silver metamaterials had better EIT-like features. At wavelengths shorter than around 650 nm, on the other hand, the aluminum metamaterials showed promising EIT-like results.

Metamaterials have attracted a great deal of attention as artificial electromagnetic materials having unique optical characteristics, and various innovative optical applications have been expected. Micro electromechanical systems (MEMS)-based reconfigurable metamaterials are candidate technologies for active optical control. In this paper, we focus on MEMS-based reconfigurable metamaterials operated in the optical region between visible and near-infrared wavelengths. A brief overview of static optical metamaterials and active optical metamaterials driven by MEMS actuators is presented. Moreover, points to be considered for a micromachining process of optical metamaterials are discussed with results of calculations.

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Fabrication of plasmonic metamaterials having electromagnetically induced transparency (EIT)-like characteristics with sharp and strong spectral responses is a challenging task for device applications at near-infrared wavelengths. EIT-like effects in silver metamaterials consisting of dipole resonators and quadrupole resonators were experimentally demonstrated, and their characteristics were evaluated. Optical characteristics of the metamaterials could be controlled by the gap distance between the two resonators. At wavelengths around 820 nm, EIT-like effects with transmittance between 72% and 28% were observed for the metamaterials with gap distances between 13 and 69 nm. At a gap of 13 nm, a maximum modulation depth of 2.29 was achieved.

For development of next-generation light control, a simple manufacturing technology to produce flexible metamaterials is a key component. Here, we report development of a printing method involving combination of a thermal nanoimprint method and a squeegeeing method, and demonstrate printed optical metamaterials made of commercially available ink consisting of silver nanoparticles. Optical evaluations of printed dipole resonators indicate dipole resonances corresponding to the structure lengths; these resonances are observed at wavelengths of 765-1346 nm. In particular, we report the important finding that, in metamaterials strongly affected by their constituent materials, a metamaterial structure made of the ink exhibits optical properties comparable to those produced by a vacuum deposition process.