title: Extension of geometrical-optics approximation to on-axis Gaussian beam scattering. I. By a spherical particle.
abstract: The geometrical-optics approximation of light scattering by a transparent or absorbing spherical particle is extended from plane wave to Gaussian beam incidence. The formulas for the calculation of the phase of each ray and the divergence factor are revised, and the interference of all the emerging rays is taken into account. The extended geometrical-optics approximation (EGOA) permits one to calculate the scattering diagram in all directions from 0 degrees to 180 degrees. The intensities of the scattered field calculated by the EGOA are compared with those calculated by the generalized Lorenz-Mie theory, and good agreement is found. The surface wave effect in Gaussian beam scattering is also qualitatively analyzed by introducing a flux ratio factor. The approach proposed is particularly important to the further extension of the geometrical-optics approximation to the scattering of large spheroidal particles.
authors.affiliation: Institute of Particle and Two-Phase Flow Measurement Technology, University of Shanghai for Science and Technology, Shanghai, China. f3_xu@yahoo.com
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.forename: Kuan Fang
authors.initials: KF
authors.lastname: Ren
authors.forename: Xiaoshu
authors.initials: X
authors.lastname: Cai