Energy-Transport, Group, and Signal Velocities near Resonance in Spatially Dispersive Media

Theoretical results are reported for energy propagation in bounded spatially dispersive (exciton-polariton) media. A remarkable slowing down of the energy-transport velocity $V_E$ is predicted near resonance. For GaAs the decrement is by a factor of ${10}^4$, with $V_E\sim 4\times {10}^3$ m/sec at resonance. Some comparison is made between energy-transport, group, and signal velocities, and available data.