The field of plasmonics—the use surface plasmons generated when photons hit a metal structure—might enable photonic circuits that could do what electronic ICs do, but do it much faster—at the speed of light. Without plasmonics, photonic circuits would be too large, because they need to accommodate wavelength of light.
In a step toward that goal, a joint research team from the University of Rochester and the Swiss Federal Institute of Technology in Zurich have developed a primitive circuit consisting of a silver nanowire and single-layer flake of molybdenum disulfide (MoS2). This simple circuit can efficiently guide both electricity and light along the same wire.
In the experiment, which was published in the journal Optica, a laser was used to trigger the plasmons on the surface of the wire. The plasmons coming off the nanowire triggered a photoluminescence in the MoS2, which is a two-dimensional material like graphene but has an inherent band gap. Excitons—basically energized electrons bound to positively charged holes that form when light hits a semiconductor—form in the MoS2, and decay into the nanowire plasmons. So, the international team demonstrated that the nanowire serves the dual purpose of exciting the MoS2 via plasmons and recollecting the decaying exciton as nanowire plasmons.
“We have found that there is pronounced nanoscale light-matter interaction between plasmons and atomically thin material that can be exploited for nanophotonic integrated circuits,” said Nick Vamivakas, assistant professor at the University of Rochester, in the press release.
The combination of subwavelength light guidiance and strong nanoscale light-matter interaction they demonstrated could help lead to compact and efficient on-chip optical processing, the researchers believe.
The next step in their research will be to demonstrate the primitive circuit with light emitting diodes.