Near-field scanning optical microscope with a metallic probe tip

Abstract

A near-field scanning optical microscope with a metallic probe tip was developed for detecting localized photons near the surface of the fine structure of a sample. In this microscope a metallic probe is used for converting the evanescent photons localized near the sample surface to the propagating scattering light wave; the scattered light is detected in the far field with external condenser optics. During the measurement the probe tip vibrates normal to the surface with an amplitude of ~5 nm at 2.5 kHz, and the light intensity modulated with this frequency is lock-in detected. This operation permits the removal of stray-light noise contribution. Experimental results of the measurements of the exponential decay of the evanescent field produced by total internal reflection are given with and without the probe vibration. Image data of the surface profile of an optical compact disk are also shown.