Enhanced reflectivity contrast in confocal solid immersion lens microscopy

The reflected image of a diffraction limited focused spot is investigated u sing confocal solid immersion microscopy. We find that the spot's image sho ws aberrations when reflected off objects with optical indexes lower than t hat of the solid immersion lens (SIL) material. We demonstrate that such ab errations are only apparent and that the actual size of the spot at the SIL /object interface remains diffraction limited. The aberrations are due to l ateral waves at the SIL surface. These von Schmidt waves originate from the total internal reflected components of a diverging spherical wave front. W e make use of this image aberration in conjunction with the spatial filteri ng inherent to confocal microscopy in order to dramatically enhance the opt ical contrast of objects with low optical indexes. (C) 2000 American Instit ute of Physics. [S0003-6951(00)00447-2].