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Keywords:

  • backscattering;
  • circular polarization;
  • helicity flip;
  • optical clearing;
  • Poincaré sphere;
  • multiple scattering;
  • random medium;
  • polarization vector

Abstract

Strong multiple scattering of light is typical for most biological tissues and leads to the loss of initial polarization, direction, phase, and wavefront of incident optical radiation. Circular polarization survives more scattering events than the direction of its propagation, whereas the helicity of backscattered optical radiation depends noticeably on the size of scattering particles. In the current study an approach of probing a disperse random medium with the use of back-scattered circular polarized light is presented. We show that the helicity flip of circular polarized light can be observed experimentally in the tissue-like media and that it is sensitive to the direction of light propagation. The flip in helicity is clearly seeing as the polarization vector traverse of the Q–U plane of the Poincaré sphere. It has been also demonstrated, for the first time in our knowledge, that the polarization changes induced by optical clearing can be clearly observed and analyzed quantitatively by tracking the polarization vectors on the Poincaré sphere. (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)