Near-field scanning optical microscope

Abstract

Near-field scanning optical microscope(NSOM) was constructed and tested by the measurement of the near-field mode of vertical cavity surface emitting lasers(VCSELs). The NSOM consists of an optical fiber tip extended to a photomultiplier tube, a two-dimensional motor-driven micrometer stage, a vertical piezoelectric translator for tip approach, a data acquisition card, and its operating program. Three kinds of technique such as chemical etching, cold-deformation, and sidewall coating were tried for the suitable aperture at the apex of the tip. To test the feasibility of the NSOM, a microscopic pattern and VCSELs were scanned with the fabricated tip. Obtained images show better resolution in comparison with those of CCD camera with a 20× microscope objective lens. Additionally, several interesting unknown behaviors of VCSELs below and near the threshold were found. The NSOM can be enhanced further by improving a tip and employing the mechanism to control the tip-sample distance such as a shear-force feedback.