Boundary diffraction waves generated from Bessel-X pulses modeled by the FDTD method

In this paper, the boundary diffraction waves generated from Bessel-X pulses passing through a thin circular aperture, a thin circular disk, and a thick circular aperture are simulated by the finite-difference time-domain (FDTD) method. Two Arago spots, which are formed from the interference of the boundary diffraction waves generated from the two branches of a Bessel-X pulse passing through the thin aperture or the thin disk, are observed clearly. The spots are shown to propagate superluminally relative to the main part of the pulse as reported previously in other papers. In particular, the boundary diffraction waves generated at the two edges located at the entrance and exit planes of the thick aperture are observed to result in four Arago spots. This observation is made possible by the fully vectorial nature of the FDTD method.