A near-field optical microscope with normal force distance regulation

Near-field imaging is a means of exceeding the diffraction limit in optical microscopy to yield subwavelength resolution optical images of a sample surface. In order to achieve such high resolution, it is necessary to scan the measurement probe above the surface at a height of only a few nanometers which requires careful control of the separation between tip and sample. In the implementation of the near-field optical microscope (NFOM) reported here, the distance regulation scheme is based on an inverted noncontact atomic force microscope (AFM) in which a cantilever is used as the sample substrate and imaging is performed with a fiber optic tip. In this way, both the benefits of AFM and NFOM are realized simultaneously.