Realization
In order to excite surface plasmons in a resonant manner, one can use an electron or light beam (visible and infrared are typical). The incoming beam has to match its momentum to that of the plasmon. In the case of p-polarized light (polarization occurs parallel to the plane of incidence), this is possible by passing the light through a block of glass to increase the wavenumber (and the momentum), and achieve the resonance at a given wavelength and angle. S-polarized light (polarization occurs perpendicular to the plane of incidence) cannot excite electronic surface plasmons. Electronic and magnetic surface plasmons obey the following dispersion relation:
where is the dielectric constant, and is the magnetic permeability of the material (1: the glass block, 2: the metal film).
Typical metals that support surface plasmons are silver and gold, but metals such as copper, titanium or chromium have also been used.
When using light to excite SP waves, there are two configurations which are well known. In the Otto setup, the light illuminates the wall of a glass block, typically a prism, and is totally internally reflected. A thin metal film (for example gold) is positioned close enough to the prism wall so that an evanescent wave can interact with the plasma waves on the surface and hence excite the plasmons.
In the Kretschmann configuration, the metal film is evaporated onto the glass block. The light again illuminates the glass block, and an evanescent wave penetrates through the metal film. The plasmons are excited at the outer side of the film. This configuration is used in most practical applications.
Read more about this topic: Surface Plasmon Resonance
Famous quotes containing the word realization:
“The ground for taking ignorance to be restrictive of freedom is that it causes people to make choices which they would not have made if they had seen what the realization of their choices involved.”
—A.J. (Alfred Jules)
“Probably nothing in the experience of the rank and file of workers causes more bitterness and envy than the realization which comes sooner or later to many of them that they are “stuck” and can go no further.”
—Mary Barnett Gilson (1877–?)
“The rush to books and universities is like the rush to the public house. People want to drown their realization of the difficulties of living properly in this grotesque contemporary world, they want to forget their own deplorable inefficiency as artists in life.”
—Aldous Huxley (1894–1963)