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Proceedings Paper

Depolarization by high-aperture focusing
Author(s): Karsten Bahlmann; Stefan W. Hell
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Paper Abstract

We propose and demonstrate a method employing ferroelectric monomolecular layers, by which it is possible to precisely measure the planar light field polarization in the focus of a lens. This method allowed us to establish for the first time to our knowledge, the perpendicularly oriented field that is anticipated at high apertures. For a numerical aperture 1.4 oil immersion lens illuminated with linearly polarized plane waves, the integral of the modulus square of the perpendicular component amounts to (1.51r0.2) % of that of the initial polarization. It is experimentally proven that depolarization decreases with decreasing aperture angle and increases when using annular apertures. Annuli formed by a central obstruction with a diameter of 89 % of that of the entrance pupil raise the integral to 5.5 %. This compares well with the value of 5.8% predicted by electromagnetic focusing theory; however, the depolarization is also due to imperfections connected with focusing by refraction. Besides fluorescence microscopy and single molecule spectroscopy, the measured intensity of the depolarized component in the focal plane is relevant to all forms of light spectroscopy combining strong focusing with polarization analysis.

Paper Details

Date Published: 15 May 2002
PDF: 9 pages
Proc. SPIE 4621, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing IX, (15 May 2002); doi: 10.1117/12.467836
Show Author Affiliations
Karsten Bahlmann, Massachusetts Institute of Technology (United States)
Stefan W. Hell, Max-Planck Institute fuer Biophysikalische Chemie (Germany)

Published in SPIE Proceedings Vol. 4621:
Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing IX
Jose-Angel Conchello; Carol J. Cogswell; Tony Wilson, Editor(s)

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