|SURFACE PLASMON RESONANCE:|
ContentsSurface wave guide
Surface plasmon resonamce
Surface plasmon wave
Differenr structures of plasmon waveguides
Metal core dielectric cladding waveguide
Metal clad waveguide
The two different medium containing different dielectric constants have different density and refractive indices. At an interface between two transparent media of different refractive index (glass and water), light coming from the side of higher refractive index is partly reflected and partly refracted. Above a certain critical angle of incidence, no light is refracted across the interface, and total internal reflection is observed. While incident light is totally reflected the electromagnetic field component penetrates a short (tens of nanometers) distance into a medium of a lower refractive index creating an exponentially attenuating evanescent wave. If the interface between the media is coated with a thin layer of metal (gold), and light is monochromatic and p-polarized, the intensity of the reflected light is reduced at a specific incident angle producing a sharp shadow (called surface plasmon resonance) due to the resonance energy transfer between evanescent wave and surface plasmons. The resonance conditions are influenced by the material absorbed onto the thin metal film. Satisfactory linear relationship is found between resonance energy and mass concentration of biochemical relevant molecules such as proteins, sugars and DNA. The SPR signal which is expressed in resonance units is therefore a measure of mass concentration at the sensor chip surface.
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