Asymptotic description of pulsed ultrawideband electromagnetic beam field propagation in dispersive, attenuative media.

The asymptotic description of the coupled spatial and temporal evolution of a pulsed ultrawideband electromagnetic beam field as it propagates through a dispersive, attenuative material that occupies the half-space z > or = z(0) is obtained from the angular spectrum of plane waves representation. This angular-spectrum representation expresses the wave field as a superposition of both homogeneous and inhomogeneous plane waves. The paraxial approximation of the spatial part of this representation for nontruncated beam fields results in a description that explicitly displays the temporal evolution of the pulsed-beam field through a single-contour integral that is of the same form as that obtained for a pulsed plane-wave field propagating in the positive z direction in a lossy, dispersive medium. The accuracy of this paraxial approximation is shown to improve as the material's attenuation increases.