Local field intensity enhancements on gold semicontinuous films investigated with an aperture nearfield optical microscope in collection mode

Optical properties of gold semicontinuous films near the percolation threshold are studied using a scanning nearfield optical microscope (SNOM) operated in a collection/transmission mode. Local field intensity enhancements due to localized surface-plasmon-polaritons are accurately observed. An intensity renormalization procedure adapted to this SNOM configuration is proposed to estimate the distribution of the enhancements. This distribution is studied for different incident wavelengths and polarizations. A statistical treatment is applied in order to obtain the probability density function of the field intensity enhancements. This function is found to decay exponentially in a wavelength dependent way.