Rays, stored energy, and power flow in dielectric waveguides*

Abstract

For light propagation in dielectric waveguides, interconnections are established between phase velocity, group velocity, stored energy, power flow, and a zigzag-ray model. The ray model takes account of the Goos–Haenchen shifts that occur at the film boundaries and of the associated time delays and predicts the correct group velocity. Relationships between group velocity, power flow, and stored energy are shown to be valid for guides of quite general cross section and in the presence of refractive-index dispersion. Except in cases of anomalous dispersion, the group velocity is generally smaller than the phase velocity.