Observation of optical resonances of dielectric spheres by light scattering

Use of the wavelength and size dependence of light scattering from optically levitated liquid drops is demonstrated as a sensitive means of detecting optical resonances of dielectric spheres. High resolution spectra are presented of the radiation pressure, far- and near-field backscatter, and 90 degrees scatter. Excellent agreement is found between experimental spectra and high resolution Mie calculations of Chylek et al. Strong evidence supporting the van de Hulst dielectric surface-wave model for these resonances is presented. Use of resonances for high precision measurement of sphere size and sphere distortion, index of refraction, temperature, and vapor pressure is discussed.