Particle-trapped near-field scanning optical microscopy: scattering and depolarization

Min Gu

doi:10.1117/12.390547

4 July 2000 Particle-trapped near-field scanning optical microscopy: scattering and depolarization

Min Gu

Proceedings Volume 4082, Optical Sensing, Imaging, and Manipulation for Biological and Biomedical Applications; (2000) https://doi.org/10.1117/12.390547
Event: Photonics Taiwan, 2000, Taipei, Taiwan

Abstract

Particle-trapped near-field scanning optical microscopy utilises a laser-trapped dielectric or metallic particle as a near-field scatterer to probe the high spatial frequency information from a sample. Scattering and depolarization by a trapped particle in an evanescent wave are two important issues in such an imaging system. These two issues are addressed in this paper. The strength of scattered evanescent waves was measured for particles of different sizes (.01 (mu) m to 2 (mu) m in diameter) and different materials (polystyrene, gold and silver). It has been found that the signal strength of scattered evanescent waves increases appreciably with the size of the particle. As a result, image contrast in improved significantly with laser-trapped metallic particles of large size. It has also been found that the depolarization of scattered evanescent waves under s polarised illumination is stronger than that under p polarized beam illumination, and that image contrast of the evanescent wave interference pattern can be improved by a factor of 3 with a parallel analyser under s polarized beam illumination. This result suggests that less depolarized scattered evanescent photons carry more information of an object and should be utilised for the imaging in particle-trapped near-field scanning optical microscopy.

Citation Download Citation

Min Gu "Particle-trapped near-field scanning optical microscopy: scattering and depolarization", Proc. SPIE 4082, Optical Sensing, Imaging, and Manipulation for Biological and Biomedical Applications, (4 July 2000); https://doi.org/10.1117/12.390547

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