Aug 22 2016
Image Credit: ssguy/Shutterstock.com
A study, published in App. Phys. Lett. 2016, DOI:10.1063/1.4959272, highlights that only a streak of light is needed to transform a metal-free metamaterial from a state that blocks specific wavelengths of light to a state that allows such restricted wavelengths to pass through.
This advancement could lead to the utilization of optoelectronic and photonic devices in the field of telecommunications and various other areas.
Unnatural properties are being observed in metamaterials, for instance, because of the geometry of their engineered structures, they are able to selectively reflect, absorb, or transmit sound or light.
An increasing number of metamaterials are being developed using metals. This includes varieties that shift between “on” and “off” states in response to a thermal stimulus or electric stimulus. These metamaterials cannot be integrated in many optical devices because metals in general tend to absorb infrared and visible light.
Kevin F. MacDonald and his team at the University of Southampton built a grating by using a 300-nm-thick film of germanium antimony telluride (Ge2Sb2Te5), or GST. This grating featured parallel lines of GST, approximately 750 nm wide and spaced apart by 130 nm. GST is a phase-change material that is mostly used in DVDs to store data.
The transmission of near-IR wavelengths ranging between 1,300 and 1,600 nm are blocked by these grating blocks. However, if this grating block is irradiated using green laser light, GST shifts from amorphous state to crystalline state, as a result of which the gratings become transparent at these wavelengths.
Currently, the team is involved in encapsulating GST between protective layers of ZnS and SiO2, as is done in DVDs, in order to prevent the grating from being damaged when it is briefly heated, thus shifting it back to its amorphous state.