ANALYSIS OF IMAGE-FORMATION WITH A PHOTON SCANNING TUNNELING MICROSCOPE

The photon scanning tunneling microscope (PSTM) is based on the frustr ation of a total internal reflected beam by the end of an optical fibe r. Until now it has been used to obtain topographic information, gener ally for smooth samples. We report theoretical as well as experimental results on the observation of a step on a quartz substrate with the P STM. These results demonstrate the effects on image formation of the d istance between the fiber tip and the sample surface, the orientation of the incident beam with respect to the step, the polarization, and t he coherence of the light. Good agreement exists between numerical sim ulations and experiments. We show that a perturbative approach, whose validity has been checked by comparison with a rigorous volume integra l method, provides physical insight into the main features of the diff erent images. (C) 1996 Optical Society of America.