COLLECTION OF FLUORESCENCE FROM SINGLE MOLECULES IN MICROSPHERES - EFFECTS OF ILLUMINATION GEOMETRY

The collection of fluorescence from a molecule inside a sphere illumin ated with single or counterpropagating plane waves is modeled. The res ults are applicable to microdroplet-based single molecule detection te chniques and to some microparticle characterization techniques using i nelastic emission. The large position-dependent variations in the fluo rescence collection rate are primarily attributable to variations in t he excitation intensity. With plane-wave illumination the collection f rom shadow regions is low because the incident energy is refracted by the droplet surface away from these regions. The average collection ra te from molecules in shadow regions can be increased by illuminating w ith counterpropagating beams. (C) 1997 Optical Society of America.