Surface waves attracted the attention of scientists already 100 years ago when researching wireless telegraphy and thereby looking into the radiation propagation along conducting surfaces. Fifty years later, accelerated charged particles were found to excite surface waves in metal foils (in addition to resonant volume oscillations of conducting electrons). These electromagnetic surface excitations coupled to electron oscillations in metals were termed as surface plasmons (SPs) and studied mainly out of academic interest until early 80-ties, when researchers realized that the intense electromagnetic fields associated with SPs generated in the vicinity of metal surfaces could be used for sensing small dielectric-constant changes associated with the adsorption of molecules on the surface. Those fields were also found to be at the heart of the enormous enhancement in the Raman spectra, which today allows researchers to resolve the chemical structure of materials even at the scale of single molecules. In photonics, however, SP modes were seen more as a nuisance because their propagation length is rather short (tens to hundreds of microns) due to energy loss by absorption into the metal.
Rapid technological developments and the demonstration of novel SP-induced phenomena during the last 10 years have changed that perception. In particular, modern nanofabrication and characterization techniques have made it possible to structure metal surfaces, so as to control the flow of SPs, and to map out features of that flow with unprecedented detail. Researchers soon realized that SP-based waveguides could transport the same huge bandwidth of information as in conventional photonics and yet not be limited by diffraction to submicron cross sections. In the effort to achieve that tantalizing vision and combine the compactness of an electronic circuit with the bandwidth of a photonic network, tackling the inevitable propagation losses became a pressing issue for practical devices and circuits. Ultimately, practical photonic circuits might use a combination of plasmonic and dielectric components, taking advantage of the best performance available.
Learn more from our review lectures on Nanoplasmonics and Plasmonic metasurfaces.