Near-field optical microscope images of a dielectric flat substrate with subwavelength strips

Abstract

In near-field scanning optical microscopy (NSOM), optical images are calculated for flat-surface samples with an optical index distribution. This makes it possible to estimate NSOM images that are free from perturbations in the topographical information of the sample. A realistic NSOM is simulated, including an aperture probe and a three-dimensional field. The calculations reveal the imaging characteristics of both the dielectric and opaque samples. We found that the NSOM images particularly under s-polarized illumination should be analyzed with the knowledge of the point spread function to avoid misinterpreting the detected images. Differences in images due to two orthogonal polarizations and incident angle of illumination are also examined.