Kinetics, morphology and pulling regimes for sensing tips in near-field microscopy

The spatial resolution provided by near-field scanning optical microscopes depends critically on the shape and size of the sharpened tip of the optical fiber used as a source of light or sensing element. The fabrication of a tip by the commonly used heating and pulling method is examined. It consists of an initially pulling and rupture followed by a cooling and relaxation. Different thermal and mechanical regimes are possible. The presented analysis leads to a deeper physical understanding of these processes and suggests avenues for technical improvements.