Near-field optical studies of semicontinuous metal films

Abstract

Local field distributions in random metal-dielectric films near a percolation threshold are experimentally studied using scanning near-field optical microscopy ͑SNOM͒. The surface-plasmon oscillations in such percolation films are localized in small nanometer-scale areas, ''hot spots,'' where the local fields are much larger than the field of an incident electromagnetic wave. The spatial positions of the hot spots vary with the wavelength and polarization of the incident beam. Local near-field spectroscopy of the hot spots is performed using our SNOM. It is shown that the resonance quality-factor of hot spots increases from the visible to the infrared. Giant local optical activity associated with chiral plasmon modes has been obtained. The hot spot's large local fields may result in local, frequency and spatially selective photomodification of percolation films.

Resonant light interaction with plasmonic nanowire systems

“…It has been shown that the metallic nanoparticles can effectively confine the optical radiation to 'nanoscale' in the proximity of plasmon resonance; the shape and position of this resonance is controlled by the shape of the nanoparticles (or their clusters) [4][5][6][7][8][9][10][11]. The broadband confinement can be achieved in metal-dielectric films [1,12,13]. Also, the resonant nanoelements can be employed to transmit the optical light at nanoscales [14,15].…”

Enhancement of two-photon photoluminescence and SERS for low-coverage gold films

“…After all, the main requirements for SERS substrates are not only high reproducibility and robust fabrication procedure, but also large-area homogeneity, low cost, and possibility for mass production. One route for the fabrication of large-area structures with "hot spots" could be realized with the semi-continuous metallic films [27][28][29]. These films can be obtained by evaporation of noble metals like gold or silver onto a dielectric or semiconductor substrate.…”

Numerical simulations of nanostructured gold films

“…Nanostructured gold films have complex behavior as the individual particles have various resonances due to their shape and local neighborhood [1,2]. In recent years electron energy loss spectroscopy (EELS) has been gaining popularity as a technique to map plasmonic resonances in nanostructures [3].…”