Near-field spectroscopy with white-light illumination

We report on near-field optical spectroscopy based on the illumination of t he sample with white light from a Xe arc lamp through a tapered optical fib er. The light transmitted through the sample is analyzed with a grating spe ctrometer in the spectral range between 400 and 750 nm. Our setup provides a unique possibility for recording detailed spectroscopic information withi n a short acquisition time. Near-field spectra acquired on gold clusters me asuring 100 nm in diameter and 20 nm in height reveal a wavelength-dependen t transmittivity with both reduced and enhanced light intensities probably stemming from surface plasmon excitation. (C) 2001 American Institute of Ph ysics.