Various properties of an electromagnetic wave whose spherical multipole expansion contains only Riccati– Neumann functions are examined. In particular, the novel behavior of the beam phase during diffractive spreading is discussed. When a Neumann beam is scattered by a spherical particle, the diffraction and external reflection portions of the scattering amplitude constructively interfere for large partial waves. As a result, a set of rapidly decreasing beam shape coefficients is required to cut off the partial wave sum in the scattering amplitudes. Because of its strong singularity at the origin, a Neumann beam can be produced by a point source of radiation at the center of a spherical cavity in a high conductivity metal, and Neumann beam scattering by a spherical particle can occur for certain partial waves if the sphere is placed at the center of the cavity as well.
© 2011 Optical Society of America
Original Manuscript: August 17, 2011
Manuscript Accepted: October 2, 2011
Published: November 17, 2011
Vol. 7, Iss. 2 Virtual Journal for Biomedical Optics
James A. Lock, "Scattering of a transversely confined Neumann beam by a spherical particle," J. Opt. Soc. Am. A 28, 2577-2587 (2011)