Surface plasmon spectroscopy of metal/dielectric structures

Surface electromagnetic waves (i.e. plasmons) were excited in metal—oxide—metal (MOM) multi-layer thin film structures by the tunnel current from an external dc source. Surface plasmons decayed to photons in the visible region with typically 10⁻¹⁰−10⁻¹²W cm⁻² light intensity.A very sensitive single channel optical spectrometer was constructed to study both spectral and angular distributions of light emitted from aluminum—oxide—noble-metal (Ag, Au, Cu) thin film diodes mounted into a cold-finger type liquid nitrogen optical cryostat. When MOM structures were prepared on substrates with regular surface modulation of 300–900 nm periods, spectral and angular measurements of the emitted light allowed one to construct the energy—wave-vector dispersion diagram of surface plasmons. This was of help in identifying the top meta/vacuum fast mode plasmons as the source of photon emission.