Graphene Enables Electrical Control of Energy Flow from Light Emitters

 Illustration of controlled energy flow from electrons into photons and plasmons (Source: ICFO)

Illustration of controlled energy flow from electrons into photons and plasmons (Source: ICFO)

Devices based on active plasmonics may exploit electron oscillations at the interfaces between materials.
Scientists from Europe’s Graphene Flagship at the Institute of Photonic Sciences ICFO in Barcelona, and the Donostia-based graphene manufacturer Graphenea have demonstrated active, in-situ electrical control of energy flow from erbium ions into photons and surface plasmons. In their experiment, erbium emitters were placed a few tens of nanometres away from a graphene sheet, the charge carrier density of which is electrically controlled.
Erbium ions are commonly used in optical amplifiers, emitting near-infrared light at 1.5 microns. This wavelength is in an important band for optical telecommunications, as there is very little energy loss in the range, and thus an efficient transmission of information.
The researchers show that energy flow from erbium into photons or plasmons can be controlled by applying a small voltage between the erbium and graphene layers. Surface plasmons in graphene are very strongly confined, with a plasmon wavelength two orders of magnitude smaller than the wavelength of emitted photons. As the charge carrier density of the graphene sheet is gradually increased, the erbium ions shift from exciting electrons in the graphene sheet to emitting photons or plasmons.
This revealed long-sought-after graphene plasmons at the near-infrared frequencies used in telecom applications. In addition, the strong concentration of optical energy observed offers new possibilities for data storage and manipulation through active plasmonic networks.
ICFO group leader and study co-author Frank Koppens says: “This work shows that electrical control of light at the nanometer scale is possible and efficient, thanks to the optoelectronics properties of graphene.” (Source: Graphene Flagship)

Reference:    K. J. Tielrooij et al.: Electrical control of optical emitter relaxation pathways enabled by graphene, Nat. Phys., online 19. January 2015, DOI: 10.1038/nphys3204

Links: Graphene Flagship

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