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Researchers from CIC nanoGUNE, in collaboration with ICFO and Graphenea, visualize for the first time infrared light in nanostructures made of graphene. This opens new opportunities for ultra-small and efficient photodetectors, sensors and other photonic and optoelectronic nanodevices. The work has been published on the cover in the prestigious scientific journal Nature Photonics.
The constant quest for compact technologies has raised a new era of nanoscience. Smarter mobile phones, faster computers, more sensitive and reliable medical tools, among others, require increasing number of sophisticated electronic elements in their built-in chips. Optical blocks, due to their much faster operation, are now seen as an alternative to semiconductor diodes and transistors. However, although light is very fast, it still cannot fit the small volumes, achievable through nanoengeneering. In fact, one of the fundamentals physical lows imposes a strong limitation on propagating light: it cannot be compressed into space smaller than a half of its wavelength, which is much larger than electronic building blocks in our electronic devices. For that reason, the ways of concentrating light to propagate it through nanoscale materials are highly demanding.
The wavelength of light captured by a graphene sheet – a monolayer sheet of carbon atoms can be shortened by a factor of 100 compared to light propagating in free space. As a consequence, this light propagating along the graphene sheet – called graphene plasmon – requires much less space. For that reason, photonic devices can be made much smaller. Graphene-based technologies enable extremely small optical nanodevices.
The light trapped inside tiny flakes of graphene (two-dimentional nano-disks and nano-rectangles) has been visualized by the researchers with the help of a state-of the-art near-field microscope. The images taken from the microscope have been interpreted with the help of computer simulations. A very rich family of ultra-compressed plasmon waves inside the nanoflakes has been discovered. These waves are very sensitive to the shapes of the nanoflakes and can be efficiently manipulated by changing the voltage applied directly to the patterned nanoflakes. “Our results pave the way to novel graphene-based technologies which could give rise to extremely small, low-power-consuming, and efficiently tunable optical nanodevices”, summarizes Ikerbasque Research Professor Rainer Hillenbrand who led the project.