IMAGING OF TEST QUARTZ GRATINGS WITH A PHOTON SCANNING TUNNELING MICROSCOPE - EXPERIMENT AND THEORY

We use the differential formalism of the electromagnetic theory of gratings to interpret the images of test sinusoidal or lamellar quartz gratings obtained with a photon scanning tunneling microscope. The period of the grating is 0.5 mu m, and the height of the rule is 0.2 mu m. It is shown that the images depend strongly on several parameters, such as polarization or angle of incidence, with respect to the ruling direction. A systematic study of the isointensity lines above the gratings as a function of polarization is presented, and it is shown that the image contrast can be increased or decreased depending on the sample-probe distance. To model the interaction of the fiber probe with the electromagnetic field, we consider a second grating facing the grating under study, and by varying the periodicity of the second grating we calculate the intensity of the collected light and compare it with the experimental results.