Tuning of surface plasmons leads to new optoelectronic devices

Surface plasmons are generated by the incident radiation, at certain frequencies, couples to the surface mode at the metal/ dielectric interface. The allowed frequencies for this coupling can be derived by solving the Maxwell's equation at such a boundary, for a given wavelength and angle of incidence of the incoming radiation. The geometry of a metal structure or the patterning of a metal film can alter the properties of the allowed surface plasmons resulting in unique absorption or transmission properties. Surface plasmons are the basis of well established technologies, such as surface-enhanced Raman spectroscopy (SERS), which has been used to demonstrate the detection of single molecules. In SERS, radiation is coupled to surface plasmons in metallic nanostructures attached to molecules, and the interaction between the surface excitation and the molecule of interest is enhanced in the near field, making SERS many order of magnitude more sensitive than traditional Raman spectroscopy.