Abstract

The optical absorption of a bulk metal is spread over a wide spectral range. In contrast, colloids consisting of the same metal show narrow absorption resonances [1]. This spectral compression of the oscillator strength is due to enhanced optical coupling to the surface plasmon modes of spherical metal particles. E.g., the transmission spectrum of a gold-film does not show clear plasmon resonances, whereas the visible absorption spectra of gold-colloids embedded in dielectric matrices are dominated by the surface plasmon resonance lying at slightly lower energy than the onset of single-particle interband transitions.

© 1996 Optical Society of America