DETECTION OF BIOLOGICAL PARTICLES BY THE USE OF CIRCULAR-DICHROISM MEASUREMENTS IMPROVED BY SCATTERING-THEORY

Light scattered from optically active spheres was theoretically analyz ed for biodetection. The circularly polarized signal of near-forward s cattering from circularly dichroic spheres was calculated. Both remote and point biodetection were considered. The analysis included the eff ect of a circular aperture and beam block at the detector. If the inci dent light is linearly polarized, a false signal would limit the sensi tivity of the biodetector. If the incident light is randomly polarized , shot noise would limit the sensitivity. Suggested improvements to cu rrent techniques include a beam block, precise angular measurements, r andomly polarized light, index-matching fluid, and larger apertures fo r large particles.