Polarization anomaly in near-field magnetooptical microscopy

The near-field magnetooptical microscopy of thin ferromagnetic films deals with the spatial distribution of intensity and polarization of light in a focused spot. We performed imaging Of Such distributions using a tungsten tip as an apertureless probe. At distances below 20 nm the tip influences the sample and can change the measured signal. This results in deviation of the experimental dependency from Fresnel formulas and ill the transformation of the electric field components parallel and perpendicular to the substrate. A model of electrostatic dipolar interaction provides a good quantitative explanation of the dependencies observed. Experimental procedures for magnetooptical near-field microscopy are derived from this model.