Abstract

The normal modes of a dielectric sphere are described by a set of vector spherical harmonics and are referred to as morphology-dependent resonances (MDR’s). These resonances occur at discrete size parameters χ_n,l = 2πa/λ_n,l, where a is the droplet radius and λ_n,l are the discrete wavelengths of the MDR’s. The MDR is characterized by a radial mode index l, an angular-momentum index n, and an azimuthal mode number, m = ±n, ±(n-1),…, 0. The spatial distribution of an m-mode MDR is mostly confined to a great circle whose normal is inclined at θ = cos⁻¹ (m/n) with respect to the z axis. For a perfect sphere [Fig. 1 (a)], each m-MDR has the same perimeter length and thus is spectrally (2n + 1) degenerate.

© 1993 Optical Society of America