Abstract: A scanning near-field optical microscope(SNOM) was used to observe rodamine 6G micro-crystal by using polarization contrast. SNOMimage with a round polarized incident light correlated well with the shear-force topography image of crystals. However, with linearly polarized light, anisotropic absorption was found. When the polarization direction was parallel to strongly absorbing direction, the optical contrast came mainly from the sample absorption, therefore, well resolution was obtained in its perpendicular direction. However, when the polarization direction was perpendicular to the strongly absorbing direction, optical contrast came mainly from the complex interaction between the near-field light and the sample, which improved the resolution in the perpendicular direction. When the direction was 45° to the absorbing direction, optical contrast came from both of the near-field interaction mechanism and the absorbing mechanism, and a good resolution image was obtained. The present work demonstrates that the polarization contrast has a great application to the studies of anisotropic materials.

Key words: Near-field optics, Scanning near field optical microscope, Polarization contrast, Anisotropic