Using a macroscopic self-consistent model for scanning near-field optical microscopy, we show that the field distribution of light emitted by an uncoated fiber tip near a sample surface consists of two spatially separated domains, of which only the central domain (near the tip end) contains evanescent-field components. The relative magnitude of the near-field contribution is found to be strongly dependent on the tip shape. Spatial resolution in near-field microscopy and lithography with uncoated fiber tips is discussed on the basis of the numerical results. Experimental results obtained on surface modification of polymer films, phase conjugation of optical near fields, and surface-polariton localization are presented. Using optical images with true optical contrast (i.e., not correlated to surface topography), we find the spatial resolution to be ~100 nm for the light wavelength of 633 nm.
© 1997 Optical Society of AmericaPDF Article