By Nick Gilbert
Purdue University researchers have discovered a way to synthesize metamaterials without using conventional gold or silver, which are expensive and incompatible with semiconductor production processes.
The researchers used aluminum-doped zinc oxide (AZO) in place of these metals, thus paving the way to realize the commercialization of hyperbolic metamaterials, which hold potential in developing advanced optical devices.
The new metamaterial developed by the Purdue research team comprises 16 alternative layers of zinc oxide and AZO. Light traversing from the zinc oxide layer to the AZO layer experiences an ‘extreme anisotropy,’ which disperses the light to turn into hyperbolic, thus causing drastic changes in the behavior of the light. Besides improving the performance, the AZO shows high-compatibility with semiconductors.
This new metamaterial can be used to fabricate a ‘planar hyperlens,’ to make powerful optical microscopes capable of viewing objects like DNA. Other potential applications include cloaking devices, quantum computing, high-efficiency solar collectors and advanced sensors.
Alexandra Boltasseva, one of the researchers, informed that the optical properties of the metamaterials containing AZO can be tuned in two ways. One way is varying the aluminum concentration in AZO. The second method involves an electrical field application to synthesize metamaterials to modify AZO’s optical properties. Thus, a new class of hyperbolic and non-hyperbolic metamaterials can be developed with this switching ability. AZO behaves like a dielectric at some wavelengths and like a metal at other wavelengths, thus enabling drastic functionality changes in the new metamaterial.
This novel metamaterial is able to function in the near-infrared spectrum range, an essential quality for optical communications. It finds use in the fabrication of next-generation light-harvesting equipment for solar power applications by enabling researchers to exploit ‘optical black holes.’ It is a plasmonic structure as it conducts plasmons. These new nanostructured material composites and plasmonic materials will advance the technology of optical metamaterials, concluded Boltasseva.