Time-dependence of backscattered intensities of a sphere illuminated with very short electromagnetic pulses

Scattered time-dependent intensities from a dielectric sphere illuminated with a very short pulsed plane wave are calculated. The time dependence of the incident pulse is considered to be a rectangular or a Gaussian function. The results are obtained for a sphere on a resonant mode. The frequency spectrum of the scattered field at a point is calculated using the incident field spectrum and the transfer function at that point. The transfer function at any frequency of the sphere at a space point is calculated using the T-matrix method. The inverse Fourier transform of the frequency spectrum is used to calculate the time-dependence of the scattered electric field. The scattered intensities are calculated for pulses of durations (~10 ps) smaller than the resonant lifetime. The computer codes are capable of calculating the scattered intensity of a shorter pulse. The computations for such shorter pulses depend on the capacity and speed of the computer system. The main factors which affect the behavior of the scattered pulse are the incident pulse spectrum (or duration) and the lifetime of the resonant mode of the sphere