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

We use the differential formalism of the electromagnetic theory of gra tings to interpret the images of test sinusoidal or lamellar quartz gr atings obtained with a photon scanning tunneling microscope. The perio d 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, suc h as polarization or angle of incidence, with respect to the ruling di rection. A systematic study of the isointensity lines above the gratin gs as a function of polarization is presented, and it is shown that th e 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.