Excitation of broadband surface plasmon polaritons: Plasmonic continuum spectroscopy

The excitation of surface plasmon polaritons in a thin metal film is extremely sensitive to the surrounding dielectric environment. We introduce here a far-field method to directly observe surface plasmon propagation and demonstrate that the lateral intensity decay length is affected by a change of the interface properties. The method relies on the detection of the intrinsic lossy modes associated with plasmon propagation in thin films. We also introduce a method to excite a broad spectral distribution of surface plasmons simultaneously throughout the visible spectrum allowing a unique form of surface plasmon-based spectroscopy.