"Swiss roll" nanostructures for optical frequency chiral metamaterials

by | Feb 6, 2015

Researchers have combined self-assembled colloid monolayers and the dynamic shadowing growth technique to fabricate arrays of Swiss roll nanostructures.

In the past decade, a new class of materials, chiral metamaterials, has emerged and developed rapidly. Due to their chiral nature, chiral metamaterials interact with left-handed and right-handed circular polarizations of light differently. This has enabled them to be applied for negative refraction, manipulation of light polarizations, chiral molecule sensing, etc. The Swiss roll structure, which is constructed by a thin insulated conducting sheet helically wound around a dielectric mandrel, was proposed in 2004 by Pendry in his seminal publication because of its ideal chirality. Such structures have been fabricated on the millimeter scale and investigated in the radio frequency region. In order to achieve Swiss roll metamaterials in the highly important optical frequency region, the dimension of the structure has to be reduced to the nanometer scale, which is a great fabrication challenge.

Recently, a group of researchers reported a simple and scalable method to fabricate arrays of Swiss roll nanostructures, by combining self-assembled colloid monolayers and the dynamic shadowing growth technique. In the obtained Swiss roll nanostructures, Ag films are helically wounded around SiO2 mandrels with SiO2 films as insulated layers. Strong chiral optical response in visible to infrared region is observed for the Swiss roll nanostructures. In addition, the dimension of the Swiss roll nanostructures can be tuned by adjusting the size of the colloid beads, which subsequently tunes the chiral optical response wavelength range. With the great advantage in scalable fabrication and tunability in structure size, this strategy can serve as a universal method to realize Swiss roll micro-/nanostructures for different applications.