Near-field optical microscope image formation: Theoretical and experimental study

A macroscopic classical theory of the c-mode near-field optical microscope (NOM) which models the optical near-field over the sample as a spectrum of plane, mostly evanescent waves and the fiber tip apex as a nanometer sized dielectric sphere was developed. The model predicts that the probe and the sample interact weakly and that the intensity picked-up by the probe is proportional to the near-field intensity. The near-field intensity over the sample has been calculated using theoretical extinction theorem. A biological specimen, microtube (MT) was chosen due to its well identified nanometric size and importance biologically. A good agreement is seen for both the MT diameter and in the observed asymmetry of the edge effect.