We report illumination-mode near-field optical microscopy images of individual 80–115-nm-diameter Au particles recorded with metal-coated fiber probes. It is found that the images are strongly influenced by the metal-coating thickness. This dependence is consistent with theoretical models, which are in good agreement with the experimental images. Probes with thick coatings (∼λ/2) produce images consisting of three extrema, owing to a resonancelike polarization of the probe end. Probes with thinner coatings generally produce simpler images. However, in some cases the images contain wavelike structures that are due to interference between direct radiation from the tip and propagating tip fields scattered by the particles.
© 1999 Optical Society of America
Original Manuscript: January 5, 1999
Revised Manuscript: March 25, 1999
Manuscript Accepted: March 25, 1999
Published: August 1, 1999
Lee J. Richter, Claire E. Jordan, Richard R. Cavanagh, Garnett W. Bryant, Ansheng Liu, Stephan J. Stranick, Christine D. Keating, and Michael J. Natan, "Influence of secondary tip shape on illumination-mode near-field scanning optical microscopy images," J. Opt. Soc. Am. A 16, 1936-1946 (1999)