Physical Interpretation of the Pulse Dynamics

Abstract

The effects of dispersion and absorption on the evolution of an electromagnetic pulse as it propagates through a homogeneous linear dielectric, developed originally by Sommerfeld [10.1] and Brillouin [10.2,3] have been described in detail by the mathematical description presented in the preceeding chapters of this monograph. The results show that after the pulse has propagated sufficiently far in the material, its dynamics settle into a relatively simple regime (known as “mature dispersion”) for the rest of the propagation. In this regime, the field becomes locally quasi-monochromatic with fixed local frequency and wave number in small regions of space which move with their own characteristic constant velocity. The theory provides approximate analytic expressions for the local wave properties to be expected at a given space-time point of observation. The expressions are very complicated, however, and neither the results nor their derivations have provided insight into the physical reasons for the field having the particular local properties it does in the various subregions of space moving with specific velocities.