COMPUTATION OF THE FIELD DIFFRACTED BY A LOCAL SURFACE DEFECT - APPLICATION TO TIP-SAMPLE INTERACTION IN THE PHOTON SCANNING TUNNELING MICROSCOPE

We use a method based on the Fourier transform of the electromagnetic field to compute the field diffracted by a local deformation of a plan e boundary surface. We give a complete development of each step of the technique. To show the interaction that exists between the probe of a near-field optical microscope and the observed sample, we use the mod el of a truncated cone-shaped tip above a rectangular surface defect. We compute the electrical intensity along a line located between the t ip and the local surface defect. We show the influence of the polariza tion of the incident wave and the effect of the position of the tip wi th respect to the position of the surface defect. (C) 1996 Optical Soc iety of America