Failure of the optical theorem for Gaussianbeam scattering by a spherical particle
Abstract
It is shown that when an electromagnetic wave with some degree of amplitude rolloff in the transverse direction is scattered by a spherical particle, the optical theorem is not valid. For such shaped beams the extinction cross section may be written as an infinite series in powers of the reciprocal of the beam width. The imaginary part of the forwardscattering amplitude is shown to be the first term in this series. Two approximations to the extinction cross section are presented for the special case of Gaussianbeam scattering. The first one is based on the dominance of diffraction in the forward direction for w_{0} \similarorgreater a , where w_{0} is the beam halfwidth and a is the target particle radius. The second approximation, valid for w_{0} \similarorless a , is based on transmissioncompensating field interference. Copyright (c) 1995 Optical Society of America
 Publication:

Journal of the Optical Society of America A
 Pub Date:
 December 1995
 DOI:
 10.1364/JOSAA.12.002708
 Bibcode:
 1995JOSAA..12.2708L
 Keywords:

 MIE THEORY;
 BEAMS;
 SCATTERING;
 PARTICLES;
 ELECTROMAGNETIC WAVES;
 EXTINCTION