Metamaterials for negative refraction: making a perfect lens

2019 edition

Mayte G├│mez Casta├▒o

Metamaterials have attracted a great deal of attention over the recent years because of the exotic electromagnetic phenomena that they can present. Their unconventional properties do not derive from their chemical composition but rather from their artificially engineered physical structure. Therefore, the proper design of their geometry and size can enable the appearance of new optical phenomena not found in nature such as negative refraction.

Besides the challenging physics behind them, metamaterials exhibiting a negative refractive index stand out for their potential application as perfect lenses, which would present an image resolution beyond the diffraction limit. A commonly studied metamaterial for this purpose is the fishnet design, which consists of a stack of metal-insulator-metal layers perforated with a periodic array of holes. Thanks to this configuration, a new magnetic response appears in the insulator layers and gives rise to a negative refractive index.

However, the implementation of such materials in nowadays technology is limited by the traditionally used top-down fabrication techniques, which involve costly and low-throughput fabrication processes. As alternative, we study the development of new inexpensive and up scalable routes to fabricate negative-index metamaterials based on low-cost techniques such as nanosphere lithography, nanoimprinting lithography and metallic electrodeposition. These new approaches open the door to the large-area fabrication of negative index metamaterials and their future implementation.