II.Surface Plasmon Resonance (SPR)

At its most basic form, the Surface Plasmon Resonance (SPR) technique is an extension of the evanescent wave interaction depicted above, in which the waveguide or a metal–dielectric interface replaces the prism. Electromagnetic waves that propagate across the interface between a dielectric organic material and a metal film are known as surface plasmons [9, 10]. Since surface plasmons propagate as a wavevector with a specific frequency band in a metal film, no light may travel across any media, and no direct excitation of surface plasmons can be achieved immediately. The most popular approach for producing a surface plasmon wave is attenuated absolute reflection (ATR).

*Nanophotonics: Fundamentals, Challenges, Future Prospects and Applied Applications DOI: http://dx.doi.org/10.5772/intechopen.98601*

#### **Figure 3.**

*Excitation of Plasmons using Kretschmann geometry [9].*

**Figure 3**, depicts the Kretschmann structure of ATR, which is commonly used to excite surface plasmons [9].
