POLARITON WAVE PACKET PROPAGATION IN THE EXCITON RESONANCE OF A SEMICONDUCTOR

This paper reports the first experimental observation of slow" pulse propagation in the exciton-polariton resonance of a direct-gap semiconductor. The propagation delay of short light pulses transmitted through a 3.7-m-thick GaAs crystal was measured directly with a cross-correlation technique. Polariton group velocities from cvac3.6 down to cvac2000 were found when the wave-packet center frequency was tuned through the n=1 exciton resonance. © 1979 The American Physical Society."