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article imageA boost for graphene-based light detectors

By Tim Sandle     May 14, 2018 in Science
Graphene functions as a light-sensitive material, which makes it suitable for light detectors. These devices can offer significant improvements over current materials presenting future possibilities for optics.
Light detection and control is essential for many types of modern device applications, such as the cameras in-built into smartphones. The potential of these optical devices can be significantly boosted if graphene is used, according to new research. For instance, graphene is capable of detecting light of almost any color. Moreover, the carbon-based material has a very fast electronic response, estimated to be within one millionth of a millionth of a second.
However, to properly design graphene-based light detectors it is necessary to understand the processes that take place inside the graphene once it absorbs light. This is the focus of the new research. The research comes from The Institute of Photonic Sciences researchers Klaas-Jan Tielrooij and ICREA Professor. The laboratory is led by Professor Dr. Frank Koppens, who specializes in studying interactions between light and matter at extreme limits.
The researchers have been assessing why graphene conductivity sometimes increases after light absorption, whereas at other times it decreases. The scientists have demonstrated that this behavior correlates with the way in which energy from absorbed light flows to the graphene electrons, which is a phenomenon that happens extremely quickly and with a very high efficiency.
Further study showed that highly doped graphene (a terms of when free electrons are present), when subject to ultrafast electron heating, triggered carriers being produced with elevated energy and to a decrease in conductivity. In contrast, weakly doped graphene (when fewer free electrons are present), then electron heating leads to the creation of additional free electrons, and a subsequent increase in conductivity. This research will advance graphene-based light detection technology.
The research findings have been published in the journal Science Advances. The research paper is "The ultrafast dynamics and conductivity of photoexcited graphene at different Fermi energies."
More about Graphene, Light, light detector, Detector
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