International research partnership develops graphene-based flat lenses
A collaborative team of researchers, led by the University of Birmingham and the National Centre for Nanoscience in Beijing have designed the world’s thinnest, tunable, lightweight lenses using graphene material. The original research paper was published in ACS Photonics on 7 January 2015.
The research represents the demonstration of a very thin and light weight lens, which is one atom layer thick. The lens is also tunable and its focusing properties can be tuned by applying an electric field and by changing the number of graphene layers. The lenses act like microscopic versions of ones used in lighthouses and could help focus light onto small pixels in cell phone cameras or a route laser light in computer chips that move data with photons instead of electron.
The project team was led by Dr Haider Butt, Lecturer in Micro Engineering and Nanotechnology from the School of Mechanical Engineering, University of Birmingham. The team designed Fresnel lenses, which are flat lenses consisting of concentric rings. The rings diffract light to create constructive interference. The other advantage of these lenses is that their optical performance can be tuned by changing the electrical properties of graphene.
The design would be key for miniaturised applications, such as in computer interconnects, because the lenses could have long focal lengths while remaining flatter, thinner, and lighter than curved lenses.
The researchers built the 50-µm-wide lenses by depositing 0.335-nm-thick layers of graphene on glass using chemical vapor deposition and then carved out the concentric circles with photolithography. The graphene rings diffract light as it passes through the lens. The team found that the intensity of the focused light doubled when they went from five-layer to 10-layer versions of the lenses.
In an applied electric field, the graphene’s ability to absorb light changed, allowing the researchers to tune the intensity of the focused light.
The lenses focused 850-nm light, in the near-infrared range; however, the team are now looking at designing lenses that work at terahertz frequencies, which have promising applications in security, spectroscopy, and biological imaging.
- The original research paper titled Graphene-Based Ultrathin Flat Lenses represents a collaborative effort between University of Birmingham (lead), University of Cambridge and National Centre for Nanoscience & Technology in Beijing.