Internal and scattered time-dependent intensity of a dielectric sphere illuminated with a pulsed Gaussian beam

Abstract

Internal and scattered time-dependent intensities are calculated for a dielectric sphere illuminated with a pulsed Gaussian beam. The center frequency of the pulse spectrum is chosen to be on, near, or far from a morphology-dependent resonance of the sphere. The center of the beam is positioned inside, on the edge, or outside the sphere. The transfer function at a point, i.e., the electric field at each frequency of the pulse spectrum, is calculated with the plane-wave spectrum technique and the T-matrix method. The frequency spectrum of the field at a point is calculated by means of the incident field spectrum and the transfer function at that point. The time dependence of the electric field at a point inside or outside the sphere is obtained by inverse Fourier transforming the frequency spectrum. Two different decay rates in the internal and the scattered time-dependent intensity are observed: a decay rate that depends on the incident pulse spectrum and a rate that depends on the line shape of the resonant mode of the sphere.