POLARIZATION EFFECTS IN REFLECTION-MODE SCANNING NEAR-FIELD OPTICAL MICROSCOPY

It is shown that the polarization state of light emitted from an apert ure-type scanning near-field optical microscopy (SNOM) tip may be sign ificantly altered on reflection from a metal surface in close proximit y (5 nm) to the tip, while remaining unchanged at distances of several microns. Proximity to dielectric surfaces produces no discernible cha nge. This effect is discussed and explained theoretically. We demonstr ate that optical image contrast of metal samples may be enhanced by us ing this effect. The mechanism of the enhancement is based on selectiv ely detecting the light emitted from the SNOM aperture and filtering o ut the light emitted through the sidewalls of the probe. It is also sh own that images of a metal grating pattern on glass show strong polari zation contrast, which may be understood in terms of simple dipole-ima ge dipole schemes and transmission-line concepts. (C) 1998 American In stitute of Physics.