Plasmonics is a specialized field of research, dealing with surface plasmon and its uses in real life. Surface plasmons are the cumulative oscillations of excited electrons taking place at the interface between a metal and a dielectric medium such as air, when light strikes the respective metal surface. One of its major applications, currently in development, is the construction of simple, nanoscale photonic circuits through which both electricity and light can pass simultaneously, at a much higher speed than in the case of conventional electronic circuits.
Such a breakthrough will indeed be instrumental in producing advanced mobile devices, capable of transferring data at the speed of light, that are based on a system using nanoscopic wires, instead of the traditionally bulky photonic integrated circuitry.
A collaborative group of researchers from the University of Rochester and the Zurich-based Swiss Federal Institute of Technology has managed to achieve this by means of a simplified circuit comprising of “a silver nanowire and a single-layer flake of molybdenum disulfide(MoS2 )”. The project, published in The Optical Society’s journal Optica, involves the bombardment of the wire surface with the help of a laser, which leads to the excitation of plasmons. These energized plasmons in turn cause the MoS2 to emit strong light, through the process of photoluminescence. On their journey backwards, the excited electrons gradually lose their energy and are once again converted to plasmons.
This concomitant passage of light and electricity takes place mainly as a result of the specific structure of molybdenum disulfide. Being a two-dimensional material like graphene, MoS2 consists of loosely bound layers, that can be easily separated from each other. In case of a single MoS2 layer, the electron-photon interaction becomes stronger and more efficient, due to the presence of energy band gaps. Consequently, the constituent electrons can easily shift between the different energy bands, by emitting photons which are in turn responsible for the corresponding photoluminescence.
In an attempt to explicate this feature of MoS2, Nick Vamivakas , quantum optics and quantum physics professor at the University of Rochester, said:
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.
The project aims to overcome the challenges faced in scaling down the size of photonic devices, which unlike electronic circuits, are larger in order to include the wavelength of light. If successful, it will lead to the development of nano-sized chips, needed for more efficient data transfer and processing.
To learn more about the project and its objectives, check the University of Rochester’s official website.
Via: IEEE Spectrum