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Surface plasmon resonance

Definition

A phenomenon that occurs when light is reflected off thin metal films. Although incident light is totally reflected, the electromagnetic field component penetrates a short (tens of nanometres) distance into a medium of a lower refractive index, thereby creating a type of wave that is known as an exponentially detenuating evanescent wave. If the interface between the media is coated with a thin layer of metal (gold), and light is monochromatic and p-polarized, the intensity of the reflected light is reduced at a specific incident angle producing a sharp shadow, called surface plasmon resonance.