Abstract

In near-field scanning optical microscopy (NSOM),¹ understanding the near-field distribution is important for the interpretation of the images. Betzig et al. have used single molecular detection to probe the near-field distribution.² In this paper, we present a new method to measure the two-dimensional intensity distribution by use of photochemical reactions. In conjugated polymers, the π-bonds are susceptible to oxidation from simultaneous exposure to oxygen and high-intensity optical radiation. During the "photo-oxidation," excessive defects are introduced into the polymers. These defects shorten the π electrons conjugated length and result in shifting of its absorption bands from visible to UV range. Photo-oxidation can be initiated on a polymer surface by application of high near-field intensity. The absorption changes will be proportional to the near-field distribution. The NSOM can then read these changes via the absorption image subsequently. Hence the process provides a new method to measure the near-field distribution from a tapered fiber tip.

© 1996 Optical Society of America