Abstract
The degree of polarization of the scattered evanescent wave is measured with a laser-trapped particle for different incident angles. It is found that depolarization under s polarized beam illumination is stronger than that under p polarized beam illumination. As a result, the contrast of the evanescent wave interference pattern imaged in a particle-trapped near-field scanning optical microscope is improved approximately by a factor of 3 with a parallel analyzer under s polarized beam illumination. The phase shift of scattered evanescent waves under s and p polarized beam illumination is determined from the measured evanescent wave interference pattern.