Experimental verification of a virtual-mode treatment for the excitation of surface plasmon polaritons by attenuated...

Attenuated-total-reflection spectra obtained by the optical excitation of surface plasmon polaritons can be interpreted in terms of two different virtual modes. It is shown that the HWHM of absorptance as a function of the incidence angle can be described by the decay constant of one of the modes. The attenuated-total-reflection resonance angle, on the other hand, is determined by the phase of another virtual mode. An experimental verification of this virtual-mode treatment is carried out for thick aluminum films.