Image formation and signal recovery in near field optical microscopy

A near-field scanning optical microscope (NSOM) changes the light field on an extremely small area of the sample surface by inserting a probe tip into the near field of the sample surface. Since the probe and the sample are very near each other, much nearer than the wavelength of incident light, near-field imaging is based on multiple scattering or interaction of photons with the total system including probe and sample. The image of an NSOM is, hence, very dependent on the gap distance between probe and sample surface, polarization of light, and nanometric distribution of structure and complex dielectric constant of sample. Nevertheless, theory of image formation has not been established. Currently people are trying to learn, from the numerically simulated experiences, how the image changes by parameters. Girard and Courjon derived representing an NSOM system with a self-consistent approach.1) Novotny et al. showed the imaging characteristics of a two-dimensional NSOM system with different samples and polarizations.2)