Researchers have created computer-based models that could yield tunable metamaterials to make an invisibility cloak1 .
The researchers have pooled data from experiments and developed theoretical models to make metamaterials whose properties can be switched. They considered a periodic array of parallel metallic nanorods with sub-wavelength periodicity. This behaves like plasma at optical and near-infrared (NIR) frequencies when exposed to radiation with electric field aligned along the rods.
When this metamaterial is embedded in an appropriate resonant medium, its plasmalike response can be switched and a transmission band opens up below the cut-off (plasma) frequency. They did simulations considering silver nanorods submerged in a background of atomic sodium gas that is readily accomplished by placing the nanorod array within a vacuum cell infused with sodium vapour.
"The research opens up a window of opportunity to make controllable metamaterials making them more flexible," says S. Anantha Ramakrishna, one of the researchers from the department of physics, Indian Institute of Technology, Kanpur. Such metamaterials raise the possibility of an invisibility cloak made of these controllable metamaterials which can be switched between visible and invisible modes, he adds.
