Experimental observation of the long-range surface-plasmon polariton

The propagation and attenuation constants of long-range surface-plasmon polaritons propagating on thin metal films have been measured for several film thicknesses by using a hemispherical retroreflecting coupler. The results are in agreement with our theoretical dispersion curves, which predict that the attenuation constant of this mode can decrease by a factor of 63 relative to that obtained with a thick metal film.