SIMULTANEOUS DETERMINATION OF SIZE AND WAVELENGTH-DEPENDENT REFRACTIVE-INDEXES OF THIN-LAYERED DROPLETS FROM OPTICAL RESONANCES

A technique for determining the size and wavelength-dependent refracti ve indices of a droplet coated with a thin layer is presented. The exi stence of a layer on the droplet is identified by a procedure that inv olves separate alignments of independently measured TE- and TM-mode re sonances with computed homogeneous- procedure also yields the mode and the order numbers associated with The observed resonances are then al igned with layered-sphere resonances of the same mode and order number s to determine the core radius, layer thickness, and constants of core acid shell dispersion formulas that minimize the difference between t he observed and the calculated positions of resonances. The technique has been tested with synthetic data with various levels of random erro rs as well as with experimental data from two droplets under identical conditions. The results show that the core radius, layer thickness, a nd core and layer refractive indices can be determined with relative e rrors of 3.5 x 10(-4), 4.5 x 10(-2), 2.3 x 10(-4), and 4.4 x 10(-3), r espectively, with the technique. (C) 1995 Optical Society of America