avelength MIM waveguides. The propagation length in a modern optical fiber is drastically larger, on the order of kilometers. The small propagation lengths of surface plasmons are a significant hurdle in the practical implementation of plasmonics; however, researchers throughout the world are actively pursuing geometries which take account for this loss and new designs to limit the loss as much as possible.
Surface plasmons have many exciting potential applications and rich underlying physics drawing heavily from solid-state physics and electrodynamics. Although known for over 50 years, there are still many unsolved theoretical and experimental problems in the field of surface plasmons. Additionally, with the use of modern nanofabrication techniques, a whole range of new plasmonic devices have become possible. Although not without their drawbacks, surface plasmon based devices have a plethora of laboratory and commercial applications--including the potential to revolutionize photonic-electronic integration with the burgeouning field of plasmonics.
Both bulk and surface plasmons have associated electromagnetic waves, and can consequently be described by Maxwell's equations. The coherent oscillations of electron motion can be encapsulated in the dielectric constant of the material. A simple model for the motion of an electron in a conductor is a free electron driven by the field of the electromagnetic wave.
This electron motion can then be converted into a dielectric constant by using the definitions of the dipole moment, electric susceptibility, and dielectric constant:
|Fig. A-1: Dispersion relation for bulk plasmons and free-space electromagnetic waves.|
&omegap is known as the plasma frequency. This dielectric constant can then be inserted into the standard electromagnetic wave equation
The wave equation allows for the standard propagating wave solution, given by
This is a valid solution provided that
This is the dispersion relation of bulk plasmon polaritons propagating in a metallic film. The dispersion relat