Graphene's unique properties can be both a blessing and a curse to researchers, especially to those at the intersection of optical and electronic applications. These single-atom thick sheets feature highly mobile electrons on their flexible profiles, making them excellent conductors, but in general graphene sheets do not interact with light efficiently.
Problematic for shorter wavelength light, photons in the near infrared region of the spectrum, where telecommunication applications become realizable. In a paper published this week in the journal Optics Letters, from The Optical Society (OSA), researchers at the Technical University of Denmark have demonstrated, for the first time, efficient absorption enhancement at a wavelength of 2 micrometers by graphene, specifically by the plasmons of nanoscale graphene disks.
Much like water ripples arising from the energy of a dropped pebble, electronic oscillations can arise in freely moving conduction electrons by absorbing light energy. The resulting collective, coherent motions of these electrons are called plasmons, which also serve to amplify the strength of the absorbed light's electric field at close proximity. Plasmons are becoming increasingly commonplace in various optoelectronic applications where highly conductive metals can be easily integrated.
Graphene plasmons, however, face an extra set of challenges unfamiliar to the plasmons of bulk metals. One of these challenges is the relatively long wavelength needed to excite them. Many efforts taking advantage of the enhancing effects of plasmons on graphene have demonstrated promise, but for low energy light.
"The motivation of our work is to push graphene plasmons to shorter wavelengths in order to integrate graphene plasmon concepts with existing mature technologies," said Sanshui Xiao, associate professor from the Technical University of Denmark.
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