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Multiple scattering in chiral media: Border effects, reduced depolarization, and sensitivity limit

par Delplancke, Françoise ;Badoz, Jacques;Boccara, Albert Claude
Référence Proceedings of SPIE - The International Society for Optical Engineering, 3121, page (465-475)
Publication Publié, 1997

Article révisé par les pairs

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Résumé :

Suspensions of polystyrene latex beads in chiral solutions were investigated. The rotatory power, induced by solubilized sucrose, in near-forward scattering was measured via a method using polarization modulation by photo-elastic modulator. The sensitivity of the measurement was enhanced and optimized in order to mesure sucrose concentrations as low a 5 mg/ml in a cell 5 mm thick only. Different concentrations and diameters of latex particles were used in combination with different sucrose concentrations going from 1 mg/ml up to saturation. The experiments showed that the apparent rotatory power is enhanced by multiple scattering, that depolarization effects are less important with highly concentrated sucrose solutions and that attention has to be paid to cell border effects in order to avoid important artifacts, in case of highly scattering suspensions. Qualitative and theoretical explanations of those observations are presented. One possible application of this method is to measure the sugar content in human blood, in vivo, non invasively, through the skin. The concentration to be evaluated is at the sensitivity limit. So any artifact has to be removed carefully, e.g. skin cell birefringence or chirality.