Optical singularities are localized regions in a light field where one or more of the field parameters, such as phase or polarization, become singular with associated zero intensity. Focused on a small spot, the electromagnetic field around the singularity has interesting characteristics, especially when it interacts with matter. The light scattered by a material object within the strongly varying optical field around the singularity is extremely sensitive to changes and can be exploited for metrology with high sensitivity and the study of physical processes on a nanometer scale. Several earlier application examples are briefly described and a more detailed presentation is provided of a novel approach to particle sizing down into the nanometer region.
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