Graphene alone has very poor light absorption — less than two percent, and research efforts have been devoted Schematic of the cavity-coupled patterned graphene. Source: University of Central FloridaSchematic of the cavity-coupled patterned graphene. Source: University of Central Floridato increasing that percentage to make the material functional. Previous studies have used metal particles on graphene sheets to show enhanced light absorption, but in those cases the majority of the light was absorbed by the metal, thus defeating the purpose. Improved light absorption would enable manufacturers to use graphene in light detectors, touchscreens, glucose testing meters and water filtration systems.

A potential solution devised at the University of Central Florida entails placing graphene on a polymer substrate and applying a polymeric stamp to form a nanoscale pattern. An optical cavity stopped light from escaping and repeatedly bounced light back to the patterned graphene layer and enhanced light absorption.

The process also allows voltage-driven change in electron energy and thus in the electron density, enabling absorption of different wavelengths of light. This makes the scheme dynamically tunable.

The researchers say their finding is of special interest to the U.S. Defense Advanced Research Projects Agency because of the need for tunable infrared cameras that can operate at room temperature and can be used to develop multispectral night vision equipment, gas and chemical sensors. A multispectral imaging capability will enable infrared imaging across various bands with the same camera, revealing further detailed information about the object — important for space exploration and many U.S. Department of Defense applications.

The research is published in the journal Physical Review B.

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