Experimental observation of plasmon–polariton waves supported by a thin metal film of finite width

What are believed to be the first experimental observations of the existence of long-range plasmon-polariton waves, guided by a thin metal film of finite width, are presented. A waveguide composed of an 8-mum-wide, 20-nm-thick, 3.5-mm-long Au metal film embedded in SiO (2) was successfully excited at a free-space wavelength of 1.55 mum in an end-fire experiment. The theoretical nature of the phenomenon is described, and experimental observations of field confinement provided by this metal waveguide are presented in detail.