Surface plasmon waves

A complementary approach to the standard reflection geometry described above uses the attenuated total reflection (ATR) geometry which couples surface plasmon waves to the incident electric field and enhances the SH production. Two configura-... 

Figure 10.1 (a) Surface plasmon wave propagating (in the x direction) along a metal-dielectric... 

Alternatively, various analytical methods based on SPR phenomenon have been developed, including surface plasmon field-enhanced Raman scattering (SERS) [7], surface plasmon field-enhanced fluorescence spectroscopy (SPFS) [8-11], surface enhanced second harmonic generation (SHG) [12], surface enhanced infrared absorption (SEIRA) [13], surface plasmon field-enhanced diffraction spectroscopy (SPDS) [14-18], Most of these methods take advantage of the greatly enhanced electromagnetic field of surface plasmon waves, in order to excite a chromophoric molecule, e.g., a Raman molecule or a fluorescent dye. Therefore, a better sensitivity is expected. 

Solving Maxwell s equations at the metal/dielectric interface at the appropriate boundary conditions yields the surface plasmon dispersion relation, that is, the relation of the angular frequency co and the x-component of the surface plasmon wave vector kSP,... 

Surface plasmon waves (SPW) have been explored almost half a century ago (23, 24). These are surface-bound electromagnetic waves propagating on the dielectric-metal interface. The existence of SPW strongly depends on the refiuctive index of the dielectric medium adjacent to the metal, so it is commonly known that the electromagnetic field of SPW is extended into the medium only to a depth of 200 nm or so (25, 26). Therefore, SPW is very suitable for the measurement of small changes in refractive index of dielectric medium in the vicinity of metal for detecting bio-molecules interaction (26-30). 

Y. Wang (2003), Wavelength selection with coupled surface plasmon waves, Appl. Phys. Lett. 82,4385-4387. 

The surface plasmon wave is excited when the resonant condition is fulfilled, i.e., the propagating vectors of both the surface plasmon (Kgp) and the... 

Surface plasmon resonance (SPR) biosensors exploit special electromagnetic waves-surface plasmon-polaritons-to probe interactions between an analyte in solution and a biomolecular recognition element immobilized on the SPR sensor surface. A surface plasmon wave can be described as a light-induced collective oscillation in electron density at the interface between a metal and a dielectric. At SPR, most incident photons are either absorbed or scattered at the metal/dielectric interface and, consequently, reflected light is greatly attenuated. The resonance wavelength and angle of incidence depend upon the permittivity of the metal and dielectric. 

Homola J, Slavik R, Ctyroky J (1997a) Intreaction between fiber modes and surface plasmon wave spectral properties. Opt Lett 22 1403-1405... 

The surface enhancement is ascribed to the occurrence of two separate effects, electromagnetic and chemical (70). The electromagnetic effect arises from small surface structures arising in the ORC that cause strong local increases of the electric fields of the excitation and scattered radiation via surface plasmon waves. The chemical effect is attributed to interactions between the adsorbed molecule and the metal surface which lead to electronic (charge-transfer) transitions between molecule and metal. The result is a res-onance-Raman-like effect. Since both effects operate only over very small distances, SERS is specific for molecules at the electrode surface. 

FIGURE 21-14 Surface plasmon resonance. Laser radiation is coupled into the glass substrate coaled with a thin metal film by a half-cylindrical prism. If total internal reflection occurs, an evanescent wave is generated in the medium of lower refractive index. This wave can exciie surface plasmon waves. When the angle Is suitable for surface plasmon resonance, a sharp decrease in the reflected intensity is observed at the detector. 

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