Classical and Quantum Surface Plasmon Resonance Biosensing

Figure 3

How the dispersion relation informs whether or not coupling can occur. (a) Diagram illustrating the propagation relationships in various media. is the surface plasmon frequency. The high-index medium is indicated by the letter “h” in the wave number k’s subscript. This shows that if the electromagnetic wave does not propagate through some high refractive index medium first before hitting the gold layer in the setup, then there would be no coupling as the propagation coefficients never meet; however, if the light goes through some high-index medium, then there will be coupling. This figure was drawn from an example in reference [42]. (b) This graphic displays the propagation relations in a Kretschmann prism configuration as well as the reasons surface plasmons at the metal-glass contact cannot be activated (coupling conditions are not satisfied). If a prism (high refractive index medium, such as a BK7 ) is incorporated into the setup and the light passes through it first, surface plasmons are excited at the metal-air interface. This is demonstrated by the intersection of the blue prism dispersion line and the red surface plasmon dispersion curve at the metal/air contact. Surface plasmons at the metal/glass contact cannot be stimulated, according to the green curve. This figure was drawn from an example figure in reference [42].

(a)

(b)