Plasmonics largely consists of the use of subwavelength metal structures to manipulate light on the subwavelength scale. A plasmon is a quantum unit of a plasma oscillation which is most readily available through the conducting electron density of metals (or semiconductors). Plasmonics often concerns the interaction of light with the conducting electron density of metals making surface plasmon polaritons (SPPs, mixed states of light and waves on the conducting electron density), although plasmons can be excited in other ways such as with electron beams. Applications include waveguides optical switching, enhanced spectroscopy of subwavelength systems (SERS, TERS, SEIRA), subwavelength optics and apertures, improved efficiency of LEDs, faster chips, cancer therapies, and chemical and biological sensors.
In the following, we introduce the concept of surface plasmon polaritons (SPPs) by showing movies.
The most typical surface plasmon-based sensor is a metal coated prism or ATR. The metal nanofilm is located between the horizontal lines in the middle of the movie frame with the prism above. If a pulse of light impinges on the metal film (through the prism, at the right wavelength and angle), surface plasmon polaritons (SPPs) can be excited at the air side (downward side) of the metal film. A three dimensional, finite difference time domain (3D-FDTD) simulation of this arrangement is shown in the movie below. Watch the electromagnetic intensity of the SPP which follows the metal film and attenuates in time long after the incident and trasmitted beams are gone.
A metal grating (bottom center) scale spacing can also excite SPPs. This 2D simulation is periodic. After the incident pulse clears, you can see SPPs travelling along the smooth metal surface next to the grating. Later you can see SPPs coming from the adjacent grating regions. Once SPPs arrive from the neighboring gratings, watch how they are coupled back out as light. If you wait long enough, you will see the same from SPPs launched two gratings away.
Our research is accomplished with metal mesh. A broadband pulse of infrared light impinges on a metal film (~2 microns thick) with a periodic array of square holes (5 micron width) on a square lattice (12.6 micron lattice parameter).
A broadband pulse of infrared light impinges on a metal film (~2 microns thick) with a periodic array of square holes (5 micron width) on a square lattice (12.6 micron lattice parameter) in which a 5 micron diameter latex sphere resides in each hole. Notice how much more intense the electromagnetic modes are within the latex sphere as opposed to the empty mesh hole. Dielectric material with the hole effectively couples to SPPs.