Lightweight Lenses Made From Graphene

An international team of researchers has made tunable, extremely lightweight lenses from graphene (ACS Photonics 2015, DOI: 10.1021/ph500197j). The lenses act like microscopic versions of ones used in lighthouses and could help focus light onto small pixels in cell phone cameras or route laser light in computer chips that move data with photons instead of electrons. Haider Butt of the University of Birmingham, in England, and colleagues based the design on Fresnel lenses, which are flat lenses consisting of concentric rings. The rings diffract light to create constructive interference, thereby focusing the light. The researchers built their 50-µm-wide lenses by depositing 0.3-nm-thick layers of graphene on glass via chemical vapor deposition and then carving concentric circles with photolithography. The team can tune the intensity of the focused light by applying an electric field to the lens, which changes graphene’s ability to absorb light. The present study demonstrated the lenses work with near-infrared light. Now the team is studying ways to focus light with terahertz frequencies, which have promising applications in security, spectroscopy, and biological imaging.