Kretschmann resonance

It is important to realize that for the plasmon resonance to occur the condition of two matching plasmons at the opposite interfaces of the thin metal must be met. In other words there must be a dielectric/metal interface at which an evanescent field is created. In the Kretschmann geometry that interface is created by having the metal coated on the glass prism. Likewise, the SPR condition can also be realized in a fiberoptic format with a thin metal layer deposited on a flattened single-mode optical... 

Fig. 2 Surface plasmon resonance device in the Kretschmann configuration, so is the refractive index of prism, ei is the refractive index of thin metal film (usually Au or Ag), 62 is the refractive index of air, and 0 represents the critical angle...

Combination of Surface Plasmon Resonance (SPR) and Optical Waveguide Spectroscopy (OWS) was used for the simultaneous determination of refractive index and film thickness of the hydrogel layers in the Kretschmann configuration [24], The resulting angle scans from the SPR instrument were fit to Fresnel calculations and different layers were represented using a simple box model. A detailed description of this process has been published previously [18]. 

Usually, there are two ways of optical excitation to achieve the resonant condition total refiection in prism-coupler structures [12] and diffraction at diffraction gratings [13]. The most commonly used is the first one due to its simplicity, and it is called the Kretschmann configuration, already shown in Fig. 5.5a. 

The potential of surface plasmons for optical sensing was recognized in the early 1980s when surface plasmons, excited in the Kretschmann geometry of the attenuated total reflection method, were used to probe processes at the surfaces of metals [1] and to detect gases [2]. Since then, numerous surface plasmon resonance (SPR) sensors have been reported. 

Figure 4. Two configurations for evanescent wave optics, (a) Top total internal reflection of a plane wave at the base of a glass prism. Bottom the reflectivity R recorded by a detector as a function of the angle of incidence shows the increase to unity at 6, the critical angle for total reflection, (b) ATR setup for the excitation of surface plasmons (PSPs) in Kretschmann geometry. Top a thin metal film (thickness 50 nm) is evaporated onto the base of the prism and acts as resonator driven by the photon field. Bottom the resonant excitation of the PSP wave is seen in the reflectivity curve as a sharp dip at coupling angle 6g.

Kretschmann E., The determination of the optical constants of metals by excitation of surface plasmon resonance, Z. Phys., 241, 313-324, 1971. 

FIGURE 4.23 Setup and principle of surface plasmon resonance (Kretschmann... 

Gwon HR, Lee SH (2010) Spectral and angular responses of surface plasmon resonance based on the Kretschmann prism configuration. Mater Trans 51 1150-1155... 

Figure 1(a) shows the Kretschmann configuration [9] for the excitation of plasmon surface polaritons (surface plasmons for short) [10] in the attenuated total reflection (ATR) mode. When a p-polarized laser beam is irradiated at the (internal) incident angle 9t from the prism of a refractive index np above 6c, a strong nonradiative electromagnetic wave, i.e. a surface plasmon is excited at the resonant angle which propagates at the metal /electrolyte interface. 

Fig. 3 Surface plasmon resonance (SPR) spectroscopy. A schematic in the Kretschmann configuration combined with an electrochemical cell.

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