Excitation of Surface Plasmon Modes

THEORETICAL BACKGROUND 2.1. Excitation of Surface Plasmon Modes 

A surface plasmon is a light wave that is bound to the interface of a metal in contact to a dielectric medium. The free electrons of the metal respond collectively by oscillating in resonance with the light wave. The interaction occurs only if the momentum of the incoming photon matches with that of the surface plasmon mode. 

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, 

This leads to the consequence that the momentum of a free photon, kph, propagating in a dielectric medium 

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