SURFACE PLASMON-POLARITON STUDY OF THE OPTICAL DIELECTRIC FUNCTION OFSILVER

The optical dielectric function of silver is measured by excitation of surface plasmon-polaritons on a silver-covered silica grating for a r ange of wavelengths in the visible region of the spectrum. By exciting the surface plasmon-polariton at the grating/silver interface the sil ver is protected from sulphidization and contamination. Comparison of angle-dependent reflectivities with grating modelling theory gives bot h the real and imaginary parts of the dielectric function of the silve r. The results compare very favourably with those obtained by other wo rkers using more conventional methods for samples held in an ultra-hig h vacuum or with protected interfaces.