Bright colors have been observed when a metal island film is deposited on top of a silver mirror with a separating quartz layer. For spacer layer thicknesses that are varied from 0 to 140 nm, the visual appearance changes from blue/black to a series of brilliant spectrumlike colors. The sequence is repeated similarly for higher interlayer thicknesses. The phenomenon is analyzed in terms of a stratified medium theory by using TEM data and an electromagnetic model for the optical constants of the metal island film. For island films with a sufficiently high absorbance (> 0.35), the spectra are characterized by two sharp minima where the reflectivity drops to values below 10−3. The observed thickness dependence is analyzed in terms of a complex combination of the phase shifts caused by the island film, the spacer, and the relevant interfaces.
© 1993 Optical Society of America
Original Manuscript: November 9, 1991
Published: January 1, 1993
Alfred Leitner, Zhensheng Zhao, Harald Brunner, Franz R. Aussenegg, and Alexander Wokaun, "Optical properties of a metal island film close to a smooth metal surface," Appl. Opt. 32, 102-110 (1993)