SPHERICAL-CAVITY-MODE ASSIGNMENTS OF OPTICAL RESONANCES IN MICRODROPLETS USING ELASTIC-SCATTERING

We describe a procedure for identifying morphology-dependent resonances observed in various optical processes in micrometer-sized droplets. This capability results from the use of a vibrating-orifice aerosol generator in which the radius a of a droplet stream is repeatedly ramped between fixed values, providing characteristic size spectra. When acquired in conjunction with other optical data (such as fluorescence, lasing, and Raman scattering), fixed-angle elastic scattering provides a fiducial spectrum from which mode positions are assigned and transferred. From Lorenz-Mie theory calculations, spectral spans of ≈0.1a are shown to be sufficient to yield unambiguous mode identification, given an initial experimental uncertainty of ±1.5° in the scattering angle and ±6% in the refractive index. © 1990 Optical Society of America.