Debashis Chanda at the University of Central Florida may have just cracked the barrier to a practical large scale metamaterial cloak in the visual spectrum. The cover story in the March edition of the journal Advanced Optical Materials, explains how Chanda and fellow optical and nanotech experts were able to develop a larger swath of multilayer 3-D metamaterial operating in the visible spectral range. They accomplished this feat by using nanotransfer printing, which can potentially be engineered to modify surrounding refractive index needed for controlling propagation of light.
“Such large-area fabrication of metamaterials following a simple printing technique will enable realization of novel devices based on engineered optical responses at the nanoscale,” said Chanda, an assistant professor at UCF.
The nanotransfer printing technique creates metal/dielectric composite films, which are stacked together in a 3-D architecture with nanoscale patterns for operation in the visible spectral range. Control of electromagnetic resonances over the 3-D space by structural manipulation allows precise control over propagation of light. Following this technique, larger pieces of this special material can be created, which were previously limited to micron-scale size.
By improving the technique, the team hopes to be able to create larger pieces of the material with engineered optical properties, which would make it practical to produce for real-life device applications. For example, the team could develop large-area metamaterial absorbers, which would enable fighter jets to remain invisible from detection systems.
The material that Chanda created can’t simply be slapped on top of a tank or plane to hide it but the printing process would allow for the faster creation of the sort of highly complex material with that capability. “You should be able to engineer that,” he said. “We looked to just engineer a bunch of properties over a big area.” One of those capabilities was partial invisibility. Specifcally, he says that the material that he and his fellow researchers made had a negative refractive index over the 400-625 nanometer wavelength range.
It could be used to hide large, stationary objects but probably not moving objects.
The technique creates stacks of metallic dielectric wafers that then merge together, chemically, called nanotransfer. “You create a stack and then another stack and you actually grow them on top of each other chemically,” Chanda explained. H said he can use this technique to print 4 inch-by-4 inch areas of metamaterial that could, in principle, be altered to deflect light.
“Printing is high throughput based on a low cost nanotransfer printing technique,” Chanda said. “Other techniques don’t allow for an easy way of making multi-layer 3D metal/dielectric stacks.”
Nanotransfer printing is used to fabricate large‐area visible 3D negative index metamaterials. Material growth aspects of nanotransfer printing are explored for multilayered metamaterials, and alternative dielectrics and deposition conditions are introduced that enabled nearly ideal geometries with excellent optical properties.
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