Plasmons are an interaction between free electrons in a metallic material and electromagnetic radiation/Surface plasmons are plasmons that are confined to travel along the interface between a metallic material and a dielectric material.
Plasmonics is an extremely broad field of study. Its applications vary from integrated optics on silicon microchips to enhancing absorption in state-of-the-art solar cells to sensing individual molecules of biohazardous materials.
Plasmons are density waves of electrons, created when light hits the surface of a metal under precise circumstances. Because these density waves are generated at optical frequencies, very small and rapid waves, they can theoretically encode a lot of information, more than what’s possible for conventional electronics.
Plasmonics is thought to embody the strongest points of both optical and electronic data transfer. Optical data transfer, as in fiber optics, allows high bandwidth, but requires bulky wires, or tubes with reflective interiors. Electronic data transfer operates at frequencies inferior to fiber optics, but only requires tiny wires. Plasmonics, sometimes called light on a wire, would allow the transmission of data at optical frequencies along the surface of a tiny metal wire, despite the fact that the data travels in the form of electron density distributions rather than photons.
The main limitation to plasmonics presently is that plasmons tend to dissipate after only a few millimeters, making them too short-lived to serve as a basis for computer chips, which are a few centimeters across.
For sending data even longer distances, the technology would need even more improvement. The key is using a material with a low refractive index, ideally negative, such that the incoming electromagnetic energy is reflected parallel to the surface of the material and transmitted along its length as far as possible.
There exists no natural material with a negative refractive index, so nanostructured materials must be used to fabricate effective plasmonic devices. For this reason, plasmonics is frequently associated with nanotechnology.
Before all-plasmonic chips are developed, plasmonics will probably be integrated with conventional silicon devices. Plasmonic wires will act as high-bandwidth freeways across the busiest areas of the chip.
Plasmonics has also been used in biosensors. When a particular protein or DNA molecule rests on the surface of a plasmon- carrying metallic material, it leaves its characteristic signature in the angle at which it reflects the energy.