Near-field scattering by dielectric spheroidal particles with sizes on the order of the illuminating wavelength

We present a theoretical study of electric field scattering by wavelength-sized spheroids. The incident, internal, and scattered fields are computed analytically by a spheroidal coordinate separation-of-variables solution, assuming axially incident monochromatic illumination. The main sources of possible numerical errors are identified and an additional point-matching procedure is implemented to provide a built-in test of the validity of the results. Numerical results were obtained for prolate and oblate particles with particular aspect ratios and sizes, and a refractive index of 1.33 relative to the surrounding medium. Special attention is paid to the characteristics of the near-field in close proximity to the spheroids. It is shown that particles with sizes close to the incident wavelength can produce high field enhancements whose spatial location and extension can be controlled by the particle geometry. (C) 2010 Optical Society of America