GENERALIZED OPTICAL THEOREM FOR ON-AXIS GAUSSIAN BEAMS

The optical theorem for an incident plane wave interacting with a fini te scatterer is generalized to the case of on-axis Gaussian beams, tak en as examples of shaped beams. Our results are restricted in this pap er to homogeneous spheres. The beams are defined by using (i) the stan dard description (ii) the localized approximation and (iii) the modifi ed localized approximation. Rigorous expressions generalizing the clas sical plane wave case expression are given and numerically discussed. A recently proposed approximation is investigated in order to point ou t assumptions underlying its validity.