Abstract

The uniform asymptotic description of the propagation of an input rectangle-modulated harmonic signal of angular frequency ω_c and initial pulse width T into the half-space z ᐳ 0 that is occupied by a single resonance Lorentz medium is described. The asymptotic description is developed by representing the input rectangular pulse as the difference between two Heaviside unit step-function modulated signals that are separated in time by the initial pulse width T. This representation clearly shows that the resultant pulse distortion in the dispersive medium is solely due to the Sommerfeld and Brillouin precursor fields that are associated with the leading and trailing edges of the input pulse. The dynamic evolution of the pulse with increasing propagation distance z ᐳ 0 is described for both long and very short initial pulse widths T. In both cases it is shown that the pulse distortion becomes severe when the propagation distance z is such that the precursor fields associated with the trailing edge of the pulse interfere with the precursor fields associated with the leading edge.

© 1987 Optical Society of America